...A acidified aqueous potassium dichromate(VI) B an alkaline solution containing complexed Cu2+...

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IB10 06_9701_11/4RP © UCLES 2010 [Turn over

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UNIVERSITY OF CAMBRIDGE INTERNATIONAL EXAMINATIONS General Certificate of Education Advanced Subsidiary Level and Advanced Level

CHEMISTRY 9701/11

Paper 1 Multiple Choice May/June 2010

1 hour

Additional Materials: Multiple Choice Answer Sheet Soft clean eraser Soft pencil (type B or HB is recommended) Data Booklet

READ THESE INSTRUCTIONS FIRST

Write in soft pencil.

Do not use staples, paper clips, highlighters, glue or correction fluid.

Write your name, Centre number and candidate number on the Answer Sheet in the spaces provided unless this has been done for you.

There are forty questions on this paper. Answer all questions. For each question there are four possible answers A, B, C and D.

Choose the one you consider correct and record your choice in soft pencil on the separate Answer Sheet.

Read the instructions on the Answer Sheet very carefully.

Each correct answer will score one mark. A mark will not be deducted for a wrong answer.

Any rough working should be done in this booklet.

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© UCLES 2010 9701/11/M/J/10

Section A

For each question there are four possible answers, A, B, C, and D. Choose the one you consider to be correct. 1 Use of the Data Booklet is relevant to this question.

What could be the proton number of an element that has three unpaired electrons in each of its atoms?

A 5 B 13 C 15 D 21 2 Use of the Data Booklet is relevant to this question.

The elements radon (Rn), francium (Fr) and radium (Ra) have consecutive proton numbers in the Periodic Table.

What is the order of their first ionisation energies?

least

endothermic

most endothermic

A Fr Ra Rn

B Fr Rn Ra

C Ra Fr Rn

D Rn Ra Fr

3 Which gas closely approaches ideal behaviour at room temperature and pressure?

A ammonia

B carbon dioxide

C helium

D oxygen

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© UCLES 2010 9701/11/M/J/10 [Turn over

4 Some bond energy values are listed below.

bond bond energy / kJ mol 1

C–H 410

C–Cl 340

Cl–Cl 244

Br–Br 193

These bond energy values relate to the following four reactions.

P Br2 → 2Br

Q 2Cl → Cl2

R CH3 + Cl → CH3Cl

S CH4 → CH3 + H

What is the order of enthalpy changes of these reactions from most negative to most positive?

A P → Q → R → S

B Q → R → S → P

C R → Q → P → S

D S → P → Q → R 5 Given the following enthalpy changes,

I2(g) + 3Cl2(g) → 2ICl3(s) ∆Ho = –214 kJ mol 1

I2(s) → I2(g) ∆Ho = +38 kJ mol 1

What is the standard enthalpy change of formation of iodine trichloride, ICl3(s)?

A +176 kJ mol 1

B –88 kJ mol 1

C –176 kJ mol 1

D –214 kJ mol 1 6 Ammonium nitrate, NH4NO3, can decompose explosively when heated.

NH4NO3 → N2O + 2H2O

What are the changes in the oxidation numbers of the two nitrogen atoms in NH4NO3 when this reaction proceeds?

A –2, –4 B +2, +6 C +4, –6 D +4, –4

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7 The Haber process for the manufacture of ammonia is represented by the following equation.

N2(g) + 3H2(g) 2NH3(g) ∆H = –92 kJ mol 1

Which statement is correct about this reaction when the temperature is increased?

A Both forward and backward rates increase.

B The backward rate only increases.

C The forward rate only increases.

D There is no effect on the backward or forward rate. 8 Use of the Data Booklet is relevant to this question.

2.920 g of a Group II metal, X, reacts with an excess of chlorine to form 5.287 g of a compound with formula XCl2.

What is metal X?

A barium

B calcium

C magnesium

D strontium

9 Which mass of gas would occupy a volume of 3 dm3 at 25 °C and 1 atmosphere pressure?

[1 mol of gas occupies 24 dm3 at 25 °C and 1 atmosphere pressure.]

A 3.2 g O2 gas

B 5.6 g N2 gas

C 8.0 g SO2 gas

D 11.0 g CO2 gas

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10 The table gives the concentrations and pH values of the aqueous solutions of two compounds, X and Y. Either compound could be an acid or a base.

X Y

concentration 2 mol dm 3 2 mol dm 3

pH 6 9

Student P concluded that X is a strong acid.

Student Q concluded that the extent of dissociation is lower in X(aq) than in Y(aq).

Which of the students are correct?

A both P and Q

B neither P nor Q

C P only

D Q only 11 Swimming pool water can be kept free of harmful bacteria by adding aqueous sodium chlorate(I),

NaOCl. This reacts with water to produce HOCl molecules which kill bacteria.

OCl (aq) + H2O OH (aq) + HOCl (aq)

In bright sunshine, the OCl ion is broken down by ultra-violet light.

OCl (aq) + uv light → Cl (aq) + ½O2(g)

Which method would maintain the highest concentration of HOCl (aq)?

A acidify the pool water

B add a solution of chloride ions

C add a solution of hydroxide ions

D bubble air through the water

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12 Na2S2O3 reacts with dilute HCl to give a pale yellow precipitate. If 1 cm3 of 0.1 mol dm 3 HCl is added to 10 cm3 of 0.02 mol dm 3 Na2S2O3 the precipitate forms slowly.

If the experiment is repeated with 1 cm3 of 0.1 mol dm 3 HCl and 10 cm3 of 0.05 mol dm 3 Na2S2O3 the precipitate forms more quickly.

Why is this?

A The activation energy of the reaction is lower when 0.05 mol dm 3 Na2S2O3 is used.

B The reaction proceeds by a different pathway when 0.05 mol dm 3 Na2S2O3 is used.

C The collisions between reactant particles are more violent when 0.05 mol dm 3 Na2S2O3 is used.

D The reactant particles collide more frequently when 0.05 mol dm 3 Na2S2O3 is used. 13 How does concentrated sulfuric acid behave when it reacts with sodium chloride?

A as an acid only

B as an acid and oxidising agent

C as an oxidising agent only

D as a reducing agent only 14 X is a salt of one of the halogens chlorine, bromine, iodine, or astatine (proton number 85).

The reaction scheme shows a series of reactions using a solution of X as the starting reagent.

X a precipitatea colourless

solution

a precipitate

HNO3(aq)

AgNO3(aq)

an excess of

dilute NH3(aq)

an excess ofHNO3(aq)

What could X be?

A sodium chloride

B sodium bromide

C potassium iodide

D potassium astatide

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15 The percentage of ammonia obtainable, if equilibrium were established during the Haber process,

is plotted against the operating pressure for two temperatures, 400 °C and 500 °C.

Which diagram correctly represents the two graphs?

A

40

20

10 20 0 0

pressure / 103 kPa

400 °C

500 °C% NH3 at equilibrium

B

40

20

10 20 0 0

pressure / 103 kPa

500 °C


C

40

20

10 20 0 0

pressure / 103 kPa

400 °C

500 °C

% NH3 at equilibrium

D

40

20

10 200 0

pressure / 103 kPa


500 °C

400 °C

16 Consecutive elements X, Y, Z are in the third period of the Periodic Table. Element Y has the

highest first ionisation energy and the lowest melting point.

What could be the identities of X, Y and Z?

A aluminium, silicon, phosphorus

B magnesium, aluminium, silicon

C silicon, phosphorus, sulfur

D sodium, magnesium, aluminium 17 Which property of Group II elements (beryllium to barium) decreases with increasing atomic

number?

A reactivity with water

B second ionisation energy

C solubility of hydroxides

D stability of the carbonates

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18 Which element of the third period requires the least number of moles of oxygen for the complete combustion of 1 mol of the element?

A aluminium

B magnesium

C phosphorus

D sodium 19 Two properties of non-metallic elements and their atoms are as follows.

property 1 has an oxide that can form a strong acid in water

property 2 has no paired 3p electrons

Which properties do phosphorus and sulfur have?

phosphorus sulfur

A 1 and 2 1 only

B 1 only 1 and 2

C 1 and 2 1 and 2

D 2 only 1 only

20 When gaseous chemicals are transported by road or by rail they are classified as follows.

flammable non-flammable poisonous

Which commonly transported gas is non-flammable?

A butane

B hydrogen

C oxygen

D propene

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21 When heated with chlorine, the hydrocarbon 2,2-dimethylbutane undergoes free radical substitution.

In a propagation step the free radical X• is formed.

CH3CH2 CH3 + Cl → X + HCl

CH3

CH3

C ●●

How many different forms of X• are possible?

A 1 B 2 C 3 D 4 22 What will react differently with the two isomeric alcohols, (CH3)3CCH2OH and

(CH3)2CHCH2CH2OH?

A acidified aqueous potassium manganate(VII)

B concentrated sulfuric acid

C phosphorus pentachloride

D sodium 23 Which reagent will give similar results with both butanone and butanal?

A acidified aqueous potassium dichromate(VI)

B an alkaline solution containing complexed Cu2+ ions (Fehling’s solution)

C an aqueous solution containing [Ag(NH3)2]+ (Tollens’ reagent)

D 2,4-dinitrophenylhydrazine reagent 24 What is formed when propanone is refluxed with a solution of NaBH4?

A propanal

B propan-1-ol

C propan-2-ol

D propane 25 Which compound is a product of the hydrolysis of CH3CO2C3H7 by boiling aqueous sodium

hydroxide?

A CH3OH B C3H7OH C C3H7CO2H D +

a NCOHC 273

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© UCLES 2010 9701/11/M/J/10

26 In many countries plastic waste is collected separately and sorted. Some of this is incinerated to provide heat for power stations.

Why is pvc, polyvinylchloride, removed from any waste that is to be incinerated?

A It destroys the ozone layer.

B It does not burn easily.

C It is easily biodegradable.

D Its combustion products are harmful. 27 Polymerisation of 1,1-dichloroethene produces a dense, high melting point substance that does

not allow gases to pass through. It is used as cling wrapping.

Which sequence appears in a short length of the polymer chain?

[ CH2CCl2CH2CCl2CH2CCl2 ]

[ CHClCHClCHClCHClCHClCHCl ]

[ CCl2CCl2CCl2CCl2CCl2CCl2 ]

[ CH2CCl2CHClCHClCH2CCl2 ]

A

B

C

D

28 When an isomer Y of molecular formula C4H9Br undergoes hydrolysis in aqueous alkali to form

an alcohol C4H9OH, the rate of reaction is found to be unaffected by changes in the concentration of OH ions present.

Which is the most likely molecular structure of Y?

A CH3CH2CH2CH2Br

B CH3CH2CHBrCH3

C (CH3)2CHCH2Br

D (CH3)3CBr 29 Which isomer of C4H10O forms three alkenes on dehydration?

A butan-1-ol

B butan-2-ol

C 2-methylpropan-1-ol

D 2-methylpropan-2-ol

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30 Which compound exhibits both cis-trans and optical isomerism?

A CH3CH=CHCH2CH3

B CH3CHBrCH=CH2

C CH3CBr=CBrCH3

D CH3CH2CHBrCH=CHBr

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© UCLES 2010 9701/11/M/J/10

Section B For each of the questions in this section, one or more of the three numbered statements 1 to 3 may be correct. Decide whether each of the statements is or is not correct (you may find it helpful to put a tick against the statements that you consider to be correct). The responses A to D should be selected on the basis of

A B C D

1, 2 and 3 are

correct

1 and 2 only are correct


1 only is

correct

No other combination of statements is used as a correct response. 31 Which diagrams represent part of a giant molecular structure?

1 2 3

= C = C = Na= Cl

32 Which reactions are redox reactions?

1 CaBr2 + 2H2SO4 → CaSO4 + Br2 + SO2 + 2H2O

2 CaBr2 + 2H3PO4 → Ca(H2PO4)2 + 2HBr

3 CaBr2 + 2AgNO3 → Ca(NO3)2 + 2AgBr 33 Sodium hydrogensulfide, NaSH, is used to remove hair from animal hides.

Which statements about the SH ion are correct?

1 It contains 18 electrons.

2 Three lone pairs of electrons surround the sulfur atom.

3 Sulfur has an oxidation state of +2.

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34 When organic refuse decomposes in water carboxylic acids are formed. The water becomes acidic and aquatic life is destroyed.

Which additives are suitable to remove this acid pollution?

1 calcium carbonate

2 calcium hydroxide

3 potassium nitrate 35 In a car engine, non-metallic element X forms a pollutant oxide Y.

Further oxidation of Y to Z occurs in the atmosphere. In this further oxidation, 1 mol of Y reacts with ½ mol of gaseous oxygen.

What can X be?

1 carbon

2 nitrogen

3 sulfur 36 Sulfur dioxide and sulfites are used in food preservation.

Why are they used for this purpose?

1 They are reducing agents so retard the oxidation of food.

2 They inhibit the growth of aerobic bacteria.

3 They react with NO2(g) converting it to NO(g). 37 Propanoic acid occurs naturally as a result of the bacterial fermentation of milk, and is partly

responsible for the flavour of Swiss cheese.

OH

O

propanoic acid

Which starting materials could be used to synthesise propanoic acid?

1 CH3CH2CH2OH

2 CH3CH2CN

3 CH3CH2CHO

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© UCLES 2010 9701/11/M/J/10

The responses A to D should be selected on the basis of

A B C D

1, 2 and 3 are

correct



1 only is

correct

No other combination of statements is used as a correct response. 38 Which structural formulae represent 2,2-dimethylpentane?

1 (CH3)2CHCH2CH(CH3)2

2 (CH3)3CCH2CH2CH3

3 CH3CH2CH2C(CH3)3 39 Which reactions are examples of nucleophilic substitution?

1 CH3CH2Br + OH → CH3CH2OH + Br

2 CH3I + H2O H

+

→ CH3OH + HI

3 CH3CH2CH2Cl + NH3 → CH3CH2CH2NH2 + HCl 40 The diagram shows some laboratory apparatus.

water

heat

Which preparations could this apparatus be used for?

1 bromoethane, from ethanol, sodium bromide and concentrated sulfuric acid

2 ethanal, from ethanol, sodium dichromate(VI) and sulfuric acid

3 1,2-dibromoethane, from bromine and ethene

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Permission to reproduce items where third party owned material protected by copyright is included has been sought and cleared where possible. Every reasonable effort has been made by the publisher (UCLES) to trace copyright holders, but if any items requiring clearance have unwittingly been included, the publisher will be pleased to make amends at the earliest possible opportunity.

University of Cambridge International Examinations is part of the Cambridge Assessment Group. Cambridge Assessment is the brand name of University of Cambridge Local Examinations Syndicate (UCLES), which is itself a department of the University of Cambridge.

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IB10 06_9701_12/2RP © UCLES 2010 [Turn over

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CHEMISTRY 9701/12


1 hour











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© UCLES 2010 9701/12/M/J/10

Section A

For each question there are four possible answers, A, B, C, and D. Choose the one you consider to be correct. 1 Which gas closely approaches ideal behaviour at room temperature and pressure?

A ammonia

B carbon dioxide

C helium

D oxygen 2 Use of the Data Booklet is relevant to this question.


A 5 B 13 C 15 D 21 3 Use of the Data Booklet is relevant to this question. The elements radon (Rn), francium (Fr) and radium (Ra) have consecutive proton numbers in the Periodic Table.


least

endothermic

most endothermic

A Fr Ra Rn

B Fr Rn Ra

C Ra Fr Rn

D Rn Ra Fr

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C–H 410

C–Cl 340

Cl–Cl 244

Br–Br 193


P Br2 → 2Br

Q 2Cl → Cl2


S CH4 → CH3 + H


A P → Q → R → S

B Q → R → S → P

C R → Q → P → S

D S → P → Q → R 5 Given the following enthalpy changes,


I2(s) → I2(g) ∆Ho = +38 kJ mol 1


A +176 kJ mol 1

B –88 kJ mol 1

C –176 kJ mol 1

D –214 kJ mol 1 6 Ammonium nitrate, NH4NO3, can decompose explosively when heated.



A –2, –4 B +2, +6 C +4, –6 D +4, –4

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A 3.2 g O2 gas

B 5.6 g N2 gas

C 8.0 g SO2 gas

D 11.0 g CO2 gas 8 Use of the Data Booklet is relevant to this question.


What is metal X?

A barium

B calcium

C magnesium

D strontium 9 The table gives the concentrations and pH values of the aqueous solutions of two compounds, X

and Y. Either compound could be an acid or a base.

X Y


pH 6 9




A both P and Q

B neither P nor Q

C P only

D Q only

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N2(g) + 3H2(g) 2NH3(g) ∆H = –92 kJ mol 1





D There is no effect on the backward or forward rate. 11 The percentage of ammonia obtainable, if equilibrium were established during the Haber process,



A

40

20

10 20 0 0

pressure / 103 kPa

400 °C


B

40

20

10 20 0 0

pressure / 103 kPa

500 °C


C

40

20

10 20 0 0

pressure / 103 kPa

400 °C

500 °C


D

40

20

10 200 0

pressure / 103 kPa


500 °C

400 °C

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© UCLES 2010 9701/12/M/J/10

12 Swimming pool water can be kept free of harmful bacteria by adding aqueous sodium chlorate(I), NaOCl. This reacts with water to produce HOCl molecules which kill bacteria.








D bubble air through the water 13 Na2S2O3 reacts with dilute HCl to give a pale yellow precipitate. If 1 cm3 of 0.1 mol dm 3 HCl is

added to 10 cm3 of 0.02 mol dm 3 Na2S2O3 the precipitate forms slowly.


Why is this?




D The reactant particles collide more frequently when 0.05 mol dm 3 Na2S2O3 is used. 14 How does concentrated sulfuric acid behave when it reacts with sodium chloride?

A as an acid only



D as a reducing agent only

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15 X is a salt of one of the halogens chlorine, bromine, iodine, or astatine (proton number 85).



solution

a precipitate

HNO3(aq)

AgNO3(aq)

an excess of

dilute NH3(aq)


What could X be?

A sodium chloride

B sodium bromide

C potassium iodide

D potassium astatide 16 Which element of the third period requires the least number of moles of oxygen for the complete

combustion of 1 mol of the element?

A aluminium

B magnesium

C phosphorus

D sodium 17 Two properties of non-metallic elements and their atoms are as follows.




phosphorus sulfur

A 1 and 2 1 only

B 1 only 1 and 2

C 1 and 2 1 and 2

D 2 only 1 only

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18 Consecutive elements X, Y, Z are in the third period of the Periodic Table. Element Y has the highest first ionisation energy and the lowest melting point.






number?




D stability of the carbonates 20 When gaseous chemicals are transported by road or by rail they are classified as follows.



A butane

B hydrogen

C oxygen

D propene 21 What will react differently with the two isomeric alcohols, (CH3)3CCH2OH and

(CH3)2CHCH2CH2OH?




D sodium

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22 Which reagent will give similar results with both butanone and butanal?




D 2,4-dinitrophenylhydrazine reagent 23 What is formed when propanone is refluxed with a solution of NaBH4?

A propanal

B propan-1-ol

C propan-2-ol

D propane 24 Which compound is a product of the hydrolysis of CH3CO2C3H7 by boiling aqueous sodium

hydroxide?


a NCOHC 273

25 When heated with chlorine, the hydrocarbon 2,2-dimethylbutane undergoes free radical

substitution.



CH3

CH3

C ●●


A 1 B 2 C 3 D 4 26 When an isomer Y of molecular formula C4H9Br undergoes hydrolysis in aqueous alkali to form

an alcohol C4H9OH, the rate of reaction is found to be unaffected by changes in the concentration of OH ions present.


A CH3CH2CH2CH2Br

B CH3CH2CHBrCH3

C (CH3)2CHCH2Br

D (CH3)3CBr

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27 Which isomer of C4H10O forms three alkenes on dehydration?

A butan-1-ol

B butan-2-ol


D 2-methylpropan-2-ol 28 Which compound exhibits both cis-trans and optical isomerism?

A CH3CH=CHCH2CH3

B CH3CHBrCH=CH2

C CH3CBr=CBrCH3

D CH3CH2CHBrCH=CHBr 29 In many countries plastic waste is collected separately and sorted. Some of this is incinerated to

provide heat for power stations.












A

B

C

D

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A B C D

1, 2 and 3 are

correct



1 only is

correct

No other combination of statements is used as a correct response. 31 Sodium hydrogensulfide, NaSH, is used to remove hair from animal hides.




3 Sulfur has an oxidation state of +2. 32 Which diagrams represent part of a giant molecular structure?

1 2 3

= C = C = Na= Cl

33 Which reactions are redox reactions?



3 CaBr2 + 2AgNO3 → Ca(NO3)2 + 2AgBr

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© UCLES 2010 9701/12/M/J/10


A B C D

1, 2 and 3 are

correct



1 only is

correct

No other combination of statements is used as a correct response. 34 When organic refuse decomposes in water carboxylic acids are formed. The water becomes

acidic and aquatic life is destroyed.


1 calcium carbonate

2 calcium hydroxide

3 potassium nitrate 35 In a car engine, non-metallic element X forms a pollutant oxide Y.


What can X be?

1 carbon

2 nitrogen

3 sulfur 36 Sulfur dioxide and sulfites are used in food preservation.




3 They react with NO2(g) converting it to NO(g). 37 Which reactions are examples of nucleophilic substitution?


2 CH3I + H2O H

+

→ CH3OH + HI

3 CH3CH2CH2Cl + NH3 → CH3CH2CH2NH2 + HCl

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© UCLES 2010 9701/12/M/J/10

38 Propanoic acid occurs naturally as a result of the bacterial fermentation of milk, and is partly responsible for the flavour of Swiss cheese.

OH

O

propanoic acid


1 CH3CH2CH2OH

2 CH3CH2CN

3 CH3CH2CHO 39 Which structural formulae represent 2,2-dimethylpentane?


2 (CH3)3CCH2CH2CH3

3 CH3CH2CH2C(CH3)3 40 The diagram shows some laboratory apparatus.

water

heat





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IB10 06_9701_13/RP © UCLES 2010 [Turn over

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CHEMISTRY 9701/13


1 hour











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© UCLES 2010 9701/13/M/J/10

Section A

For each question there are four possible answers, A, B, C, and D. Choose the one you consider to be correct. 1 Which gas closely approaches ideal behaviour at room temperature and pressure?

A ammonia

B carbon dioxide

C helium

D oxygen 2 Use of the Data Booklet is relevant to this question.

The elements radon (Rn), francium (Fr) and radium (Ra) have consecutive proton numbers in the Periodic Table.


least

endothermic

most endothermic

A Fr Ra Rn

B Fr Rn Ra

C Ra Fr Rn

D Rn Ra Fr

3 Use of the Data Booklet is relevant to this question.


A 5 B 13 C 15 D 21 4 Given the following enthalpy changes,


I2(s) → I2(g) ∆Ho = +38 kJ mol 1


A +176 kJ mol 1

B –88 kJ mol 1

C –176 kJ mol 1

D –214 kJ mol 1

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C–H 410

C–Cl 340

Cl–Cl 244

Br–Br 193


P Br2 → 2Br

Q 2Cl → Cl2


S CH4 → CH3 + H


A P → Q → R → S

B Q → R → S → P

C R → Q → P → S

D S → P → Q → R



A 3.2 g O2 gas

B 5.6 g N2 gas

C 8.0 g SO2 gas

D 11.0 g CO2 gas 7 Ammonium nitrate, NH4NO3, can decompose explosively when heated.



A –2, –4 B +2, +6 C +4, –6 D +4, –4

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© UCLES 2010 9701/13/M/J/10


N2(g) + 3H2(g) 2NH3(g) ∆H = –92 kJ mol 1





D There is no effect on the backward or forward rate. 9 Use of the Data Booklet is relevant to this question.


What is metal X?

A barium

B calcium

C magnesium

D strontium 10 The table gives the concentrations and pH values of the aqueous solutions of two compounds, X

and Y. Either compound could be an acid or a base.

X Y


pH 6 9




A both P and Q

B neither P nor Q

C P only

D Q only

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11 How does concentrated sulfuric acid behave when it reacts with sodium chloride?

A as an acid only



D as a reducing agent only 12 Swimming pool water can be kept free of harmful bacteria by adding aqueous sodium chlorate(I),

NaOCl. This reacts with water to produce HOCl molecules which kill bacteria.








D bubble air through the water 13 Na2S2O3 reacts with dilute HCl to give a pale yellow precipitate. If 1 cm3 of 0.1 mol dm 3 HCl is

added to 10 cm3 of 0.02 mol dm 3 Na2S2O3 the precipitate forms slowly.


Why is this?




D The reactant particles collide more frequently when 0.05 mol dm 3 Na2S2O3 is used.

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© UCLES 2010 9701/13/M/J/10

14 X is a salt of one of the halogens chlorine, bromine, iodine, or astatine (proton number 85).



solution

a precipitate

HNO3(aq)

AgNO3(aq)

an excess of

dilute NH3(aq)


What could X be?

A sodium chloride

B sodium bromide

C potassium iodide

D potassium astatide 15 The percentage of ammonia obtainable, if equilibrium were established during the Haber process,



A

40

20

10 20 0 0

pressure / 103 kPa

400 °C


B

40

20

10 20 0 0

pressure / 103 kPa

500 °C


C

40

20

10 20 0 0

pressure / 103 kPa

400 °C

500 °C


D

40

20

10 200 0

pressure / 103 kPa


500 °C

400 °C

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16 Two properties of non-metallic elements and their atoms are as follows.




phosphorus sulfur

A 1 and 2 1 only

B 1 only 1 and 2

C 1 and 2 1 and 2

D 2 only 1 only

17 Consecutive elements X, Y, Z are in the third period of the Periodic Table. Element Y has the

highest first ionisation energy and the lowest melting point.






number?




D stability of the carbonates 19 Which element of the third period requires the least number of moles of oxygen for the complete

combustion of 1 mol of the element?

A aluminium

B magnesium

C phosphorus

D sodium

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20 When gaseous chemicals are transported by road or by rail they are classified as follows.



A butane

B hydrogen

C oxygen

D propene 21 What will react differently with the two isomeric alcohols, (CH3)3CCH2OH and

(CH3)2CHCH2CH2OH?




D sodium 22 What is formed when propanone is refluxed with a solution of NaBH4?

A propanal

B propan-1-ol

C propan-2-ol

D propane 23 When heated with chlorine, the hydrocarbon 2,2-dimethylbutane undergoes free radical

substitution.



CH3

CH3

C ●●


A 1 B 2 C 3 D 4

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24 Which reagent will give similar results with both butanone and butanal?




D 2,4-dinitrophenylhydrazine reagent 25 Which compound is a product of the hydrolysis of CH3CO2C3H7 by boiling aqueous sodium

hydroxide?


a NCOHC 273

26 Which compound exhibits both cis-trans and optical isomerism?

A CH3CH=CHCH2CH3

B CH3CHBrCH=CH2

C CH3CBr=CBrCH3

D CH3CH2CHBrCH=CHBr 27 In many countries plastic waste is collected separately and sorted. Some of this is incinerated to

provide heat for power stations.












A

B

C

D

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29 When an isomer Y of molecular formula C4H9Br undergoes hydrolysis in aqueous alkali to form an alcohol C4H9OH, the rate of reaction is found to be unaffected by changes in the concentration of OH ions present.


A CH3CH2CH2CH2Br

B CH3CH2CHBrCH3

C (CH3)2CHCH2Br

D (CH3)3CBr 30 Which isomer of C4H10O forms three alkenes on dehydration?

A butan-1-ol

B butan-2-ol


D 2-methylpropan-2-ol

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A B C D

1, 2 and 3 are

correct



1 only is

correct

No other combination of statements is used as a correct response. 31 Which reactions are redox reactions?



3 CaBr2 + 2AgNO3 → Ca(NO3)2 + 2AgBr 32 Sodium hydrogensulfide, NaSH, is used to remove hair from animal hides.




3 Sulfur has an oxidation state of +2. 33 Which diagrams represent part of a giant molecular structure?

1 2 3

= C = C = Na= Cl

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A B C D

1, 2 and 3 are

correct



1 only is

correct

No other combination of statements is used as a correct response. 34 In a car engine, non-metallic element X forms a pollutant oxide Y.


What can X be?

1 carbon

2 nitrogen

3 sulfur 35 When organic refuse decomposes in water carboxylic acids are formed. The water becomes

acidic and aquatic life is destroyed.


1 calcium carbonate

2 calcium hydroxide

3 potassium nitrate 36 Sulfur dioxide and sulfites are used in food preservation.




3 They react with NO2(g) converting it to NO(g). 37 Which structural formulae represent 2,2-dimethylpentane?


2 (CH3)3CCH2CH2CH3

3 CH3CH2CH2C(CH3)3

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38 Which reactions are examples of nucleophilic substitution?


2 CH3I + H2O H

+

→ CH3OH + HI

3 CH3CH2CH2Cl + NH3 → CH3CH2CH2NH2 + HCl 39 Propanoic acid occurs naturally as a result of the bacterial fermentation of milk, and is partly

responsible for the flavour of Swiss cheese.

OH

O

propanoic acid


1 CH3CH2CH2OH

2 CH3CH2CN

3 CH3CH2CHO 40 The diagram shows some laboratory apparatus.

water

heat





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This document consists of 11 printed pages and 1 blank page.

DC (SHW 00422 3/09) 11740/2© UCLES 2010 [Turn over

UNIVERSITY OF CAMBRIDGE INTERNATIONAL EXAMINATIONSGeneral Certificate of Education Advanced Subsidiary Level and Advanced Level


Write your name, Centre number and candidate number on all the work you hand in.Write in dark blue or black pen.You may use a pencil for any diagrams, graphs, or rough working.Do not use staples, paper clips, highlighters, glue or correction fluid.DO NOT WRITE ON ANY BARCODES.

Answer all questions.You may lose marks if you do not show your working or if you do not use appropriate units.A Data Booklet is provided.

The number of marks is given in brackets [ ] at the end of each question or part question.At the end of the examination, fasten all your work securely together.

*1565076543*

CHEMISTRY 9701/21

Paper 2 Structured Questions AS Core May/June 2010

1 hour 15 minutes

Candidates answer on the Question Paper.

Additional Materials: Data Booklet

For Examiner’s Use

1

2

3

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Answer all the questions in the spaces provided.

1 Elements and compounds which have small molecules usually exist as gases or liquids.

(a) Chlorine, Cl 2, is a gas at room temperature whereas bromine, Br 2, is a liquid under the same conditions.

Explain these observations.

..........................................................................................................................................

..........................................................................................................................................

.................................................................................................................................... [2]

(b) The gases nitrogen, N2, and carbon monoxide, CO, are isoelectronic, that is they have the same number of electrons in their molecules.

Suggest why N2 has a lower boiling point than CO.

..........................................................................................................................................

..........................................................................................................................................

.................................................................................................................................... [2]

(c) A ‘dot-and-cross’ diagram of a CO molecule is shown below. Only electrons from outer shells are represented.

C O

In the table below, there are three copies of this structure. On the structures, draw a circle round a pair of electrons that is associated with each of

the following.

(i) a co-ordinate bond (ii) a covalent bond (iii) a lone pair

C O C O C O

[3]

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(d) Hydrogen cyanide, HCN, is a gas which is also isoelectronic with N2 and with CO. Each molecule contains a strong triple bond with the following bond energies.

bond bond energy / kJ mol–1

–C�N in HCN 890

N�N 994

C�O 1078

Although each compound contains the same number of electrons and a strong triple bond in its molecule, CO and HCN are both very reactive whereas N2 is not.

Suggest a reason for this.

..........................................................................................................................................

.................................................................................................................................... [1]

(e) HCN reacts with ethanal, CH3CHO.

(i) Give the displayed formula of the organic product formed.

(ii) What type of reaction is this?

...................................................................

(iii) Draw the mechanism of this reaction. You should show all full and partial charges and represent the movement of electron pairs by curly arrows.

[5]

[Total: 13]

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2 The diagram below shows, for a given temperature T, a Boltzmann distribution of the kinetic energy of the molecules of a mixture of two gases that will react together, such as nitrogen and hydrogen.

The activation energy for the reaction, Ea, is marked.

Ea energy

number ofmolecules

(a) On the graph above,

(i) draw a new distribution curve, clearly labelled T�, for the same mixture of gases at a higher temperature, T�;

(ii) mark clearly, as H, the position of the activation energy of the reaction at the higher temperature, T�.

[3]

(b) Explain the meaning of the term activation energy.

..........................................................................................................................................

..........................................................................................................................................

..........................................................................................................................................

.................................................................................................................................... [2]

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The reaction between nitrogen and hydrogen to produce ammonia in the Haber process is an example of a large-scale gaseous reaction that is catalysed.

(c) (i) State the catalyst used and give the operating temperature and pressure of the Haber process.

catalyst ......................................................

temperature ...............................................

pressure ....................................................

(ii) On the energy axis of the graph opposite, mark the position, clearly labelled C, of the activation energy of the reaction when a catalyst is used.

(iii) Use your answer to (ii) to explain how the use of a catalyst results in reactions occurring at a faster rate.

..................................................................................................................................

..................................................................................................................................

..................................................................................................................................[3]

(d) Two reactions involving aqueous NaOH are given below.

CH3CHBrCH3 + NaOH CH3CH(OH)CH3 + NaBr reaction 1

HCl + NaOH NaCl + H2O reaction 2

In order for reaction 1 to occur, the reagents must be heated together for some time. On the other hand, reaction 2 is almost instantaneous at room temperature.

Suggest brief explanations why the rates of these two reactions are very different.

reaction 1 ........................................................................................................................

..........................................................................................................................................

..........................................................................................................................................

reaction 2 ........................................................................................................................

..........................................................................................................................................

.................................................................................................................................... [4]

[Total: 12]

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3 This question refers to the elements shown in the portion of the Periodic Table given below.

H HeLi Be B C N O F Ne

Na Mg Al Si P S Cl ArK Ca Sc Ti V Cr Mn Fe Co Ni Cu Zn Ga Ge As Se Br Kr

(a) From this table, identify in each case one element that has the property described. Give the symbol of the element in each case.

(i) The element that has a molecule which contains exactly eight atoms.

............................................................

(ii) The element that forms the largest cation.

............................................................

(iii) An element that floats on water and reacts with it.

............................................................

(iv) An element that reacts with water to give a solution that can behave as an oxidising agent.

............................................................

(v) An element whose nitrate gives a brown gas on thermal decomposition.

............................................................[5]

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(b) (i) Give the formula of the oxide of the most electronegative element.

............................................................

(ii) Several of these elements form more than one acidic oxide. Give the formulae of two such oxides formed by the same element.

.......................... and .........................[3]

The formulae and melting points of the fluorides of the elements in Period 3, Na to Cl, are given in the table.

formula of fluoride NaF MgF2 Al F3 SiF4 PF5 SF6 Cl F5

m.p. / K 1268 990 1017 183 189 223 170

(c) (i) Suggest the formulae of two fluorides that could possibly be ionic.

..................................................................................................................................

(ii) What is the shape of the SF6 molecule?

............................................................

(iii) In the sequence of fluorides above, the oxidation number of the elements increases from NaF to SF6 and then falls at Cl F5.

Attempts to make Cl F7 have failed but IF7 has been prepared. Suggest an explanation for the existence of IF7 and for the non-existence of Cl F7.

..................................................................................................................................

..................................................................................................................................

..................................................................................................................................[4]

[Total: 12]

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4 (a) Complete the following reaction scheme which starts with propene. In each empty box, write the structural formula of the organic compound that would

be formed.

A

CH3CH=CH2KMnO4 /H+Br2

cold, dilute

NH3

in an excess

KCN in

aqueousethanol

B

D C F

E G

H2SO4(aq)heat under

reflux

NaOH(in ethanol)heat under

reflux

HBr

[7]

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(b) Under suitable conditions, compound E will react with compound B.

(i) What functional group is produced in this reaction?

............................................................

(ii) How is this reaction carried out in a school or college laboratory?

..................................................................................................................................

..................................................................................................................................[3]

[Total: 10]

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5 Isomerism occurs in many organic compounds. The two main forms of isomerism are structural isomerism and stereoisomerism. Many organic compounds that occur naturally have molecules that can show stereoisomerism, that is cis-trans or optical isomerism.

(a) (i) Explain what is meant by structural isomerism.

..................................................................................................................................

..................................................................................................................................

(ii) State two different features of molecules that can give rise to stereoisomerism.

..................................................................................................................................

..................................................................................................................................[3]

Unripe fruit often contains polycarboxylic acids, that is acids with more than one carboxylic acid group in their molecule.

One of these acids is commonly known as tartaric acid, HO2CCH(OH)CH(OH)CO2H.

(b) Give the structural formula of the organic compound produced when tartaric acid is reacted with an excess of NaHCO3.

[1]

Another acid present in unripe fruit is citric acid,

HO2CCH2CCH2CO2H

CO2H

OH

(c) Does citric acid show optical isomerism? Explain your answer.

..........................................................................................................................................

..........................................................................................................................................

.................................................................................................................................... [1]

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A third polycarboxylic acid present in unripe fruit is a colourless crystalline solid, W, which has the following composition by mass: C, 35.8%; H, 4.5%; O, 59.7%.

(d) (i) Show by calculation that the empirical formula of W is C4H6O5.

(ii) The Mr of W is 134. Use this value to determine the molecular formula of W.

[3]

A sample of W of mass 1.97 g was dissolved in water and the resulting solution titrated with 1.00 mol dm–3 NaOH. 29.4 cm3 were required for complete neutralisation.

(e) (i) Use these data to deduce the number of carboxylic acid groups present in one molecule of W.

(ii) Suggest the displayed formula of W.

[5]

[Total: 13]

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University of Cambridge International Examinations is part of the Cambridge Assessment Group. Cambridge Assessment is the brand name of University of Cambridge Local Examinations Syndicate (UCLES), which is itself a department of he University of Cambridge.

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UNIVERSITY OF CAMBRIDGE INTERNATIONAL EXAMINATIONSGeneral Certificate of EducationAdvanced Subsidiary Level and Advanced Level





*3828945530*

CHEMISTRY 9701/22


1 hour 15 minutes




1

2

3

4

5

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ForExaminer’s

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1 In the 19th and 20th centuries, experimental results showed scientists that atoms consist of a positive, heavy nucleus which is surrounded by electrons.

Then in the 20th century, theoretical scientists explained how electrons are arranged in

orbitals around atoms.

(a) The diagram below represents the energy levels of the orbitals present in atoms of the second period (Li to Ne).

(i) Label the energy levels to indicate the principal quantum number and the type of orbital at each energy level.

ener

gy

(ii) On the axes below, draw a sketch diagram of one of each different type (shape) of orbital that is occupied by the electrons in a second-period element.

Label each type.

zy

x

zy

x

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(iii) Complete the electronic configurations of nitrogen atoms and oxygen atoms on the energy level diagrams below.

Use arrows to represent electrons.

ener

gyen

ergy

nitrogen

oxygen [6]

(b) (i) Use the Data Booklet to state the value of the first ionisation energy of nitrogen and of oxygen.

N ............................... kJ mol–1 O ............................... kJ mol–1

(ii) Explain, with reference to your answer to (a)(iii), the relative values of these two ionisation energies.

..................................................................................................................................

..................................................................................................................................

.................................................................................................................................. [3]

[Total: 9]

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2 Copper, proton number 29, and argon, proton number 18, are elements which have different physical and chemical properties.

In the solid state, each element has the same face-centred cubic crystal structure which is shown below.

The particles present in such a crystal may be atoms, molecules, anions or cations. In the diagram above, the particles present are represented by .

(a) Which types of particle are present in the copper and argon crystals? In each case, give their formula.

element particle formula

copper

argon

[2]

At room temperature, copper is a solid while argon is a gas.

(b) Explain these observations in terms of the forces present in each solid structure.

..........................................................................................................................................

..........................................................................................................................................

..........................................................................................................................................

..........................................................................................................................................

..........................................................................................................................................

.................................................................................................................................... [4]

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Although copper is a relatively unreactive element, when it is heated to a high temperature in an excess of chlorine, copper(II) chloride is formed.

When a mixture of argon and chlorine is heated to a high temperature, no reaction occurs.

(c) (i) How does chlorine behave in its reaction with copper?

..................................................................................................................................

(ii) Suggest a reason for the lack of a reaction between argon and chlorine.

..................................................................................................................................

.................................................................................................................................. [2]

The melting points of the noble gases neon to xenon are given below.

Ne Ar Kr Xe

melting point /K 25 84 116 161

(d) Explain why there is an increase in melting point from neon to xenon.

..........................................................................................................................................

..........................................................................................................................................

.................................................................................................................................... [2]

[Total: 10]

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3 The table below gives data for some of the oxides of Period 3 elements.

oxide Na2O MgO Al 2O3 SiO2 P4O6 SO2

melting point /°C 1275 2827 2017 1607 24 –75

bonding

structure

(a) Complete the table by filling in

(i) the ‘bonding’ row by using only the words ‘ionic’ or ‘covalent’,

(ii) the ‘structure’ row by using only the words ‘simple’ or ‘giant’. [2]

(b) From the table of oxides above, suggest the formula of one oxide that is completely insoluble in water.

................... [1]

(c) Separate samples of Na2O and SO2 were added to water.

(i) For each oxide, write a balanced equation for its reaction with water and suggest a numerical value for the pH of the resulting solution.

Na2O

equation ...................................................................................................................

pH ............

SO2

equation ...................................................................................................................

pH ............

(ii) Construct a balanced equation for the reaction that occurs when a solution of Na2O in water reacts with a solution of SO2 in water.

.................................................................................................................................. [5]

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(d) Separate samples of the oxides MgO and SiO2 are melted. Each molten sample is then tested to see whether or not it conducts electricity.

Suggest what would be the results in each case. Explain your answers.

MgO .................................................................................................................................

..........................................................................................................................................

..........................................................................................................................................

SiO2 .................................................................................................................................

..........................................................................................................................................

.......................................................................................................................................... [4]

[Total: 12]

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4 An organic compound, E, has the following composition by mass: C, 48.7%; H, 8.1%; O, 43.2%.

(a) Calculate the empirical formula of E.

[2]

(b) When vaporised in a suitable apparatus, 0.130 g of E occupied a volume of 58.0 cm3 at 127 °C and 1.00 × 105 N m–2.

(i) Use the expression pV = mRTMr

to calculate Mr of E,

where m is the mass of E.

(ii) Hence calculate the molecular formula of E.

[4]

(c) Compound F, is an ester with the molecular formula C4H8O2.

F is one of four isomers, S, T, U, and V, that are all esters.

In the boxes below, the structural formula of S is given.

Draw the structural formulae of the other three isomers of F that are esters.

HCO2CH(CH3)2

S T U V

[3]

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(d) When the ester F is hydrolysed, an alcohol G is produced.

(i) What reagent can be used to hydrolyse an ester to an alcohol? ...................................

(ii) What other type of organic compound is produced at the same time?

................................... [2]

(e) On mild oxidation, the alcohol G gives a compound H which forms a silver mirror with Tollens’ reagent.

(i) What functional group does the reaction with Tollens’ reagent show to be present in compound H? Give the name of this group.

...................................

(ii) What type of alcohol is G?

.........................................

(iii) What could be the structural formula of the alcohol G?

[3]

(f) (i) Which of the four isomers, S, T, U, or V, could not be F?

.........................................

(ii) Explain your answer.

..................................................................................................................................

.................................................................................................................................. [2]

[Total: 16]

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5 Alkenes such as propene can be readily prepared from alcohols in a school or college laboratory by using the apparatus below.

mineral woolsoaked withthe alcohol

strong heat

Xpropene

water

(a) (i) Give the name of an alcohol that can be used in this apparatus to prepare propene.

.......................................................

(ii) Draw the skeletal formula of the alcohol you have named in (i).

(iii) What type of reaction occurs in this case?

....................................................... [3]

(b) (i) During the reaction, the material X becomes black in colour. Suggest the identity of the black substance and suggest how it is produced during

the reaction.

..................................................................................................................................

..................................................................................................................................

..................................................................................................................................

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(ii) At the end of the experiment, when no more propene is being produced, the delivery tube is removed from the water before the apparatus is allowed to cool.

Suggest why this done.

..................................................................................................................................

..................................................................................................................................

..................................................................................................................................

(iii) The material labelled X can be broken crockery, broken brick or pumice.

Give the chemical formula of a compound that is present in one of these materials.

..............................

(iv) State another reagent that could be used to produce propene from an alcohol.

....................................................... [5]

(c) Give the structural formula of the organic product formed when propene reacts separately with each of the following substances.

(i) bromine

(ii) cold, dilute manganate(VII) ions

(iii) hot, concentrated manganate(VII) ions

[3]

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(d) Propene may be polymerised.

(i) What is the essential condition for such a polymerisation?

.......................................................

(ii) The disposal of waste poly(propene) is very difficult. Give one important reason for this.

..................................................................................................................................

.................................................................................................................................. [2]

[Total: 13]



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UNIVERSITY OF CAMBRIDGE INTERNATIONAL EXAMINATIONSGeneral Certificate of EducationAdvanced Subsidiary Level and Advanced Level





*7524377035*

CHEMISTRY 9701/23


1 hour 15 minutes




1

2

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1 Hydrazine, N2H4, can be used as a rocket fuel and is stored as a liquid. It reacts exothermically with oxygen to give only gaseous products.

The enthalpy change of a reaction such as that between hydrazine and oxygen may be calculated by using standard enthalpy changes of formation.

(a) Define the term standard enthalpy change of formation, ΔHf .

..........................................................................................................................................

..........................................................................................................................................

.................................................................................................................................... [3]

(b) Hydrazine reacts with oxygen according to the following equation.

N2H4(l) + O2(g) N2(g) + 2H2O(g)

(i) Use the data in the table to calculate the standard enthalpy change of this reaction.

compound ΔHf /kJ mol–1

N2H4(l) 50.6

H2O(g) –241.8

ΔH = ........................................ kJ mol–1

(ii) Although the above reaction is highly exothermic, hydrazine does not burn spontaneously in oxygen.

Suggest a reason for this.

..................................................................................................................................

..................................................................................................................................

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(iii) Suggest why using hydrazine as a rocket fuel could be regarded as being ‘environmentally friendly’.

..................................................................................................................................

.................................................................................................................................. [4]

(c) The bonding in hydrazine is similar to that in ammonia.

(i) Showing outer-shell electrons only, draw a ‘dot-and-cross’ diagram of an ammonia molecule.

(ii) Draw a diagram to show the three-dimensional shape of an ammonia molecule.

(iii) Draw a diagram to show the shape of a hydrazine molecule. Show clearly which atom is joined to which and show clearly the value of one bond

angle.

[4]

(d) Deduce the oxidation state of nitrogen in hydrazine.

.......................................... [1]

[Total: 12]

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2 The alkali metals are a series of six elements in Group I of the Periodic Table. The first ionisation energy of these elements shows a marked trend as the Group is descended.

(a) Define the term first ionisation energy.

..........................................................................................................................................

..........................................................................................................................................

.................................................................................................................................... [2]

(b) (i) State and explain the trend in first ionisation energy as Group I is descended.

..................................................................................................................................

..................................................................................................................................

..................................................................................................................................

(ii) Suggest how this trend helps to explain the increase in the reactivity of the elements as the Group is descended.

..................................................................................................................................

.................................................................................................................................. [3]

(c) In a redox reaction, 0.83 g of lithium reacted with water to form 0.50 dm3 of aqueous lithium hydroxide.

2Li(s) + 2H2O(l) 2LiOH(aq) + H2(g)

(i) Calculate the amount, in moles, of lithium that reacted.

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(ii) Calculate the volume of hydrogen produced at room temperature and pressure.

(iii) Calculate the concentration, in mol dm–3, of the LiOH(aq) formed.

[5]

(d) When heated in chlorine, all of the alkali metals react to form the corresponding chloride.

Describe what you see when sodium is heated in chlorine and write a balanced equation for the reaction.

description

..........................................................................................................................................

..........................................................................................................................................

..........................................................................................................................................

equation

.......................................................................................................................................... [2]

[Total: 12]

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3 This question refers to the elements shown in the section of the Periodic Table below.

H He

Li Be B C N O F Ne

Na Mg Al Si P S Cl Ar

K Ca Sc Ti V Cr Mn Fe Co Ni Cu Zn Ga Ge As Se Br Kr

(a) From this list of elements, identify in each case one element that has the property described. Give the symbol of the element.

(i) an element that sinks in cold water and reacts readily with it

.............

(ii) an element that forms an oxide that is a reducing agent

.............

(iii) the element that has the largest first ionisation energy

.............

(iv) the metal in Period 3 (Na to Ar) that has the smallest cation

.............

(v) the element which has a giant molecular structure and forms an oxide which also has a giant molecular structure

.............

(vi) the element in Period 3 (Na to Ar) with the greatest electrical conductivity

............. [6]

(b) From the section of the Periodic Table above, identify two elements whose hydrides form hydrogen bonds between their molecules.

............. and ............. [1]

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(c) Use the elements in Period 3 (Na to Ar) in the section of the Periodic Table opposite to identify the oxide(s) referred to below.

In each case, give the formula of the oxide(s).

(i) an oxide which has no reaction with water

.............

. (ii) two acidic oxides formed by the same element

............. and .............

(iii) an oxide which dissolves readily in water to give a strongly alkaline solution

.............

(iv) an oxide which is amphoteric

............. [5]

[Total: 12]

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4 Organic reactions involve substances which may be

atoms, molecules, ions or free radicals.

We also apply the terms

electrophilic, nucleophilic, addition, elimination and substitution

to organic reactions.

Consider the following reactions.

CH4 + Cl 2 CH3Cl + HCl reaction 1

CH3CH2OH CH2=CH2 + H2O reaction 2

CH3I + OH– CH3OH + I – reaction 3

CH3COCH3 + HCN CH3C(OH)(CN)CH3 reaction 4

(a) Using the terms mentioned above, state as clearly as you can the nature of each of the following reactions.

reaction 1 .......................................................................

reaction 2 ....................................................................... [2]

(b) By considering the four reactions above, suggest a formula for each of the following substances.

In each case, state which reaction you are considering.

(i) one substance that is an addition product

reaction....... addition product

(ii) one substance that is a leaving group

reaction....... leaving group

(iii) one substance that behaves as an electrophile

reaction....... electrophile

[3]

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(c) What is meant by the term nucleophile?

..........................................................................................................................................

.................................................................................................................................... [1]

(d) Reactions 3 and 4 involve nucleophiles. For each reaction, give the formula of the nucleophile.

reaction 3

reaction 4

[2] (e) One characteristic reaction of ethene is its ability to decolourise bromine.

CH2=CH2 + Br2 BrCH2CH2Br

In this reaction, ethene behaves as a nucleophile.

Suggest an explanation for how ethene can behave in this way.

..........................................................................................................................................

.................................................................................................................................... [1]

[Total: 9]

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5 Lactic acid, 2-hydroxypropanoic acid, CH3CH(OH)CO2H, occurs naturally in sour milk and in our muscles when we take hard exercise.

Lactic acid is chiral and shows stereoisomerism.

(a) Draw fully displayed structures of the two optical isomers of lactic acid. Indicate with an asterisk (*) the chiral carbon atom in the lactic acid molecule.

[3]

(b) Lactic acid may be synthesised from ethanol by the following route.

CH3CH2OH step 1

CH3CHO step 2

CH3CH(OH)CN step 3

CH3CH(OH)CO2H

Give the reagent(s) and essential condition(s) for each step.

reagent(s) condition(s)

step 1

step 2

step 3

[6]

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During exercise, lactic acid is produced in our muscles from pyruvic acid, CH3COCO2H. This reaction occurs in the presence of the enzyme lactic acid dehydrogenase.

(c) (i) What type of chemical compound is the enzyme lactic acid dehydrogenase?

.................................................

(ii) How would you detect a small quantity of pyruvic acid in a sample of lactic acid?

State the reagent(s) you would use and what would be seen in your test.

reagent(s) .................................................................................................................

observation ...............................................................................................................

(iii) How would you detect a small quantity of lactic acid in a sample of pyruvic acid?

State the reagent(s) you would use and what would be seen in your test.

reagent(s) .................................................................................................................

observation ...............................................................................................................

(iv) What chemical reagent would be used to convert pyruvic acid into lactic acid?

CH3COCO2H CH3CH(OH)CO2H

................................................. [6]

[Total: 15]

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DC (SJF5445/CGW) 11612/5© UCLES 2010 [Turn over



Write your Centre number, candidate number and name on all the work you hand in.Give details of the practical session and laboratory where appropriate, in the boxes provided.Write in dark blue or black pen.You may use a soft pencil for any diagrams, graphs or rough working.Do not use staples, paper clips, highlighters, glue or correction fluid.DO NOT WRITE IN ANY BARCODES.

Answer all questions.You may lose marks if you do not show your working or if you do not use appropriate units.Use of a Data Booklet is unnecessary.

Qualitative Analysis Notes are printed on pages 10 and 11.

At the end of the examination, fasten all your work securely together.The number of marks is given in brackets [ ] at the end of each question orpart question.

*2141916687*

CHEMISTRY 9701/31

Paper 31 Advanced Practical Skills May/June 2010

2 hours


Additional Materials: As listed in the Instructions to Supervisors


1

2

Total

Session

Laboratory

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1 Read through question 1 before starting any practical work.

You are provided with the following reagents. FA 1, 2.0 mol dm–3 sulfuric acid, H2SO4 FA 2, aqueous sodium hydroxide, NaOH

The reaction of sulfuric acid with sodium hydroxide is exothermic. In separate experiments you will add increasing volumes of FA 2 to a fixed volume of

FA 1. In each experiment you will measure the maximum temperature rise. As the volume of FA 2 is increased, this maximum temperature rise will increase and then decrease.

By measuring the maximum temperature rise for different mixtures of the two reagents you are to determine the following.

• the concentration of sodium hydroxide, NaOH, in FA 2 • the enthalpy change when 1 mol of H2SO4 is neutralised by NaOH

(a) Method

• Fill the burette with FA 1. • Support the plastic cup in the 250 cm3 beaker. • Run 10.00 cm3 of FA 1 from the burette into the plastic cup. • Measure 10 cm3 of FA 2 in a measuring cylinder. • Place the thermometer in the FA 2 in the measuring cylinder and record the steady

temperature of the solution. • Tip the FA 2 in the measuring cylinder into the plastic cup, stir and record the

maximum temperature obtained in the reaction. • Empty and rinse the plastic cup. Rinse the thermometer. Shake dry the plastic cup. • Carry out the experiment four more times. Each time use 10.00 cm3 of FA 1. Use 20 cm3, 30 cm3, 40 cm3 and 50 cm3 of FA 2 in these different experiments.

Carry out two further experiments. Choose volumes of FA 2 which will allow you to investigate more precisely the volume

of FA 2 that produces the highest temperature rise when added to 10.00 cm3 of FA 1.

Results Record your results in an appropriate form showing, for each experiment, the volumes of solution used, temperature measurements and the temperature rise.

[9]

i

ii

iii

iv

v

vi

vii

viii

ix

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(b) Use the grid below to plot a graph of temperature rise (y-axis) against the volume of FA 2 added (x-axis).

Draw a line of best fit through the points where the temperature rise is increasing and another line through the points where the temperature rise is decreasing.

The intersection of these lines represents the temperature rise for the volume of FA 2 that exactly neutralises the sulfuric acid present in 10.00 cm3 of FA 1.

[4]

i

ii

iii

iv

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(c) Read from the graph the volume of FA 2 that gives the maximum temperature rise.

The volume of FA 2 giving the maximum temperature rise is ………….. cm3. [1]

(d) Explain why the temperature rise is plotted on the y-axis rather than on the x-axis.

..........................................................................................................................................

...................................................................................................................................... [1]

(e) Construct the balanced equation for the reaction of sulfuric acid with sodium hydroxide.

...................................................................................................................................... [1]

(f) (i) Calculate how many moles of sulfuric acid, H2SO4, are contained in 10.00 cm3 of FA 1.

10.00 cm3 of FA 1 contain ………….. mol of H2SO4.

(ii) Calculate how many moles of NaOH are required to neutralise the amount of H2SO4 calculated in (i) above.

The sulfuric acid in 10.00 cm3 of FA 1 is neutralised by ………… mol of NaOH. [2]

(g) Use the equation below to calculate the concentration of NaOH in FA 2.

concentration of NaOH (mol dm–3) = answer to (f)(ii) × 1000volume of FA 2 (cm3) from (c)

The concentration of NaOH in FA 2 = ………………………. mol dm–3. [1]

(h) Read the maximum temperature rise from the graph and use this to calculate the enthalpy change when 1 mol H2SO4 is neutralised by NaOH. Give your answer in kJ mol–1 and include the correct sign for the reaction.

[4.3 J are absorbed or released when the temperature of 1 cm3 of solution changes by 1 °C. Remember that separate volumes of FA 1 and FA 2 were mixed together.]

ΔH = ……………………… kJ mol–1. [2]

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(i) A student suggested that the accuracy of the experiment would be improved if the volume of FA 2 had been measured using a burette rather than a measuring cylinder.

Suggest an advantage and a disadvantage of using a burette in the procedure.

advantage ........................................................................................................................

..........................................................................................................................................

disadvantage ...................................................................................................................

..........................................................................................................................................[2]

(j) Identify two further significant sources of error, other than the measurement of volume, in the experiments used for measuring temperature rise.

error 1 ..............................................................................................................................

..........................................................................................................................................

error 2 ..............................................................................................................................

..........................................................................................................................................[1]

(k) Complete the sections below.

(i) The maximum error in taking a temperature reading on a thermometer with

graduations at 1 °C is ………………°C.

(ii) The temperature rise when 30 cm3 of FA 2 is added to 10.00 cm3 of FA 1

is ………………°C.

(iii) Calculate the maximum percentage error due to the thermometer when measuring the temperature rise in (ii) above.

The maximum percentage error = ……………… %.[2]

[Total: 26]

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2 Solutions FA 3, FA 4 and FA 5 each contain a Group 2 halide. Solution FA 6 contains a potassium salt.

You will carry out tests to deduce the following. • the anion present in FA 6 • the solution containing the chloride ions • the solution containing barium ions

At each stage of any test you are to record details of the following. • colour changes seen • the formation of any precipitate and the colour of the precipitate

Where gases are released they should be identified by a test, described in the appropriate place in your observations.

You should indicate clearly at what stage in a test a change occurs. Marks are not given for chemical equations. No additional tests for ions present should be attempted.

If any solution is warmed directly with a Bunsen burner a boiling-tube MUST be used. Rinse and reuse test-tubes where possible.

(a) Use information from the Qualitative Analysis Notes on page 11 to select a pair of reagents that, used together, identify the halide ion present.

The reagents are ……………………………..………… followed by ……………………………..………… . [1]

(b) Use your chosen reagents to carry out tests on FA 3, FA 4 and FA 5. Record your results in an appropriate form in the space below.

[2]

(c) From the results of the tests in (b) state which solution contains the chloride ion, Cl –.

Solution ………….. contains the chloride ion.

Explain the evidence that supports your conclusion.

..........................................................................................................................................

...................................................................................................................................... [1]

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(d) Carry out the following tests on each of the solutions FA 3, FA 4 and FA 5. Record your observations below.

testobservations

FA 3 FA 4 FA 5

To 1 cm depth of solution in a test-tube, add 2 cm depth of aqueous sodium hydroxide.

To 1 cm depth of solution in a test-tube, add 2 cm depth of aqueous ammonia.

To 1 cm depth of solution in a test-tube, add 1 cm depth of FA 6.

[3]

(e) To 1 cm depth of FA 6 in a test-tube add 1 cm depth of dilute sulfuric acid.

observation

..........................................................................................................................................

...................................................................................................................................... [1]

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(f) From your observations in (d) and (e) you should be able to identify the anion in FA 6 and which of the solutions FA 3, FA 4 or FA 5 contains barium cations.

The anion present in FA 6 is ………………………. .

Ba2+ ions are contained in solution ………………………. .

Explain how your observations support your conclusions for

(i) the anion present in FA 6, .......................................................................................

.................................................................................................................................

(ii) the solution containing Ba2+ ions. ............................................................................

................................................................................................................................. [1]

Read through the remainder of question 2 before starting further practical work.

Heat a half-full 250 cm3 beaker of water for use as a hot water-bath.

(g) FA 7, FA 8, FA 9 and FA 10 are organic compounds. Each contains one of the following different functional groups.

• primary alcohol • tertiary alcohol • aldehyde • ketone

You are to react some of these compounds with some of the following reagents. • acidified aqueous potassium dichromate(VI) • 2,4-dinitrophenylhydrazine (2,4-DNPH) reagent • ammoniacal silver nitrate (Tollens’ reagent)

You are provided with the first two reagents. You must prepare the last of these reagents, Tollens’ reagent, immediately before use. Follow the instructions in the box below.

To 2 cm depth of aqueous silver nitrate in a boiling-tube add ½ cm depth of aqueous sodium hydroxide. This will produce a brown precipitate of silver(I) oxide. Add aqueous ammonia a little at a time, with continuous shaking, until the brown precipitate just dissolves. Do not add an excess of aqueous ammonia.

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In each of the following tests add a few drops of the reagent to 1 cm depth of FA 7, FA 8, FA 9 and FA 10 in separate test-tubes.

In the tests using acidified potassium dichromate(VI) and Tollens’ reagent, if no initial reaction is seen, warm that tube and its contents in your hot water-bath. There is no need to heat any tube to which you have added 2,4-DNPH reagent.

Do not heat any tube with a naked flame.

Record your results in the table below.

Do not carry out tests for the shaded boxes.

reagentobservations

FA 7 FA 8 FA 9 FA 10

acidified potassium dichromate(VI)

2,4-DNPH reagent

Tollens’ reagent

[3]

(h) State which of the solutions contains a tertiary alcohol. Explain the observations leading to your conclusion.

FA …………… contains the tertiary alcohol.

explanation ......................................................................................................................

..........................................................................................................................................

State which of the solutions contains the aldehyde. Explain the observations leading to your conclusion.

FA …………… contains the aldehyde.

explanation ......................................................................................................................

.......................................................................................................................................... [2]

[Total: 14]

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Key: [ ppt. = precipitate. ]

1 Reactions of aqueous cations

ionreaction with

NaOH(aq) NH3(aq)

aluminium,

Al 3+(aq)

white ppt.

soluble in excess

white ppt.

insoluble in excess

ammonium,

NH4+(aq)

no ppt.

ammonia produced on heating–

barium,

Ba2+(aq)no ppt. (if reagents are pure) no ppt.

calcium,

Ca2+(aq)white ppt. with high [Ca2+(aq)] no ppt.

chromium(III),Cr3+(aq)

grey-green ppt. soluble in excess

giving dark green solution

grey-green ppt.

insoluble in excess

copper(II),Cu2+(aq)

pale blue ppt.

insoluble in excess

blue ppt. soluble in excess

giving dark blue solution

iron(II),Fe2+(aq)

green ppt. turning brown on contact with air

insoluble in excess


insoluble in excess

iron(III),Fe3+(aq)

red-brown ppt.

insoluble in excess

red-brown ppt.

insoluble in excess

lead(II),Pb2+(aq)

white ppt.

soluble in excess

white ppt.

insoluble in excess

magnesium,

Mg2+(aq)

white ppt.

insoluble in excess

white ppt.

insoluble in excess

manganese(II),Mn2+(aq)

off-white ppt. rapidly turning brown on contact with air

insoluble in excess


insoluble in excess

zinc,

Zn2+(aq)

white ppt.

soluble in excess

white ppt.

soluble in excess

[Lead(II) ions can be distinguished from aluminium ions by the insolubility of lead(II) chloride.]

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2 Reactions of anions

ion reaction

carbonate,

CO32–

CO2 liberated by dilute acids

chromate(VI),

CrO42– (aq)

yellow solution turns orange with H+(aq);

gives yellow ppt. with Ba2+(aq);

gives bright yellow ppt. with Pb2+(aq)

chloride,

Cl– (aq)

gives white ppt. with Ag+(aq) (soluble in NH3(aq));

gives white ppt. with Pb2+(aq)

bromide,

Br– (aq)

gives cream ppt. with Ag+(aq) (partially soluble in NH3(aq));


iodide,

I– (aq)

gives yellow ppt. with Ag+(aq) (insoluble in NH3(aq));

gives yellow ppt. with Pb2+(aq)

nitrate,

NO3– (aq)

NH3 liberated on heating with OH-(aq) and Al foil

nitrite,

NO2– (aq)

NH3 liberated on heating with OH-(aq) and Al foil;

NO liberated by dilute acids(colourless NO → (pale) brown NO2 in air)

sulfate,

SO42– (aq)

gives white ppt. with Ba2+(aq) or with Pb2+(aq) (insoluble in excess dilute strong acids);

sulfite,

SO32– (aq)

SO2 liberated with dilute acids;

gives white ppt. with Ba2+(aq) (soluble in excess dilute strong acids)

3 Tests for gases

gas test and test result

ammonia, NH3 turns damp red litmus paper blue

carbon dioxide, CO2 gives a white ppt. with limewater(ppt. dissolves with excess CO2)

chlorine, Cl2 bleaches damp litmus paper

hydrogen, H2 “pops” with a lighted splint

oxygen, O2 relights a glowing splint

sulfur dioxide, SO2 turns acidified aqueous potassium dichromate(VI) from orange to green

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DC (LEO/SW) 23111/3© UCLES 2010 [Turn over

*8263371454*







CHEMISTRY 9701/33


2 hours




1

2

Total

Session

Laboratory

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1 You are required to determine the molar enthalpy change of solution for ammonium chloride, FA 1.

When an exothermic reaction takes place in a container such as a beaker, some of the evolved heat energy is absorbed by the beaker.

When an endothermic reaction takes place some of the required heat energy is supplied by the beaker.

The amount of heat energy evolved or supplied for a 1 °C change in temperature is known as the heat capacity of the beaker.

In preparation for your experiment to determine the molar enthalpy change of solution for FA 1 you will first need to determine the approximate heat capacity of a 250 cm3 beaker.

Before starting any practical work read through the instructions in (a) and draw up a table to record your results.

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(a) Determining the approximate heat capacity of the 250 cm3 beaker

When samples of hot and cold water are mixed in the 250 cm3 beaker, some heat is lost to the beaker in raising its temperature. To determine the approximate heat capacity of your 250 cm3 beaker, you will determine the maximum temperature rise when a sample of hot water is added to cold water in the beaker.

• Use a 50 cm3 measuring cylinder to transfer 50 cm3 of cold water into the 250 cm3

beaker. • Use the 50 cm3 measuring cylinder to transfer 50 cm3 of cold water into a 100 cm3

beaker. Note the temperature of the water in this 100 cm3 beaker and heat it carefully and gently until the temperature of the water in it has increased by 45–50 °C then stop heating, e.g. if the water is at 20.0 °C you should warm it to 65–70 °C.

• Stir the cold water in the 250 cm3 beaker with the thermometer. • Record the temperature of the cold water (this is the temperature at t = 0 min). • Record the temperature each minute for 3 minutes.

• After you have taken the reading at t = 3 min, use the thermometer to stir the hot water in the 100 cm3 beaker.

• At t = 4 min, measure the temperature of the hot water and record this value in the box below.

• Immediately add the hot water from the 100 cm3 beaker to the cold water in the 250 cm3 beaker. Stir with the thermometer but do not record the temperature.

• Continue to stir the water throughout the experiment. • Record the temperature at t = 5 min, and then every ½ minute until t = 8 min. • Empty and rinse the 250 cm3 beaker. Dry it using a paper towel. • Record all measurements of time and temperature obtained.

The temperature, T1, of the hot water at t = 4 min is ………… °C.

Table of results

[3]

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(b) Graph plotting 1. Plot a graph of the temperature of the water in the 250 cm3 beaker (y-axis) against

time (x-axis) on the grid below. Do not plot the temperature, T1, of the hot water at t = 4 min. 2. Draw two straight lines of best fit; one through the points up to t = 3 min; the second

through the points from t = 5 min to t = 8 min. Extrapolate both lines to t = 4 min. 3. From the extrapolated lines read the minimum and the maximum temperatures at

t = 4 min. Record these values in the spaces provided below. 4. Determine the values for the two temperature changes at t = 4 min.

Minimum temperature, T2, at t = 4 min is ............... °C.

Maximum temperature, T3, at t = 4 min is ............... °C.

Temperature rise for 50 cm3 of cold water in the 250 cm3 beaker, (T3 – T2) is ............... °C.

Temperature fall for 50 cm3 of hot water from the 100 cm3 beaker, (T1 – T3) is ............... °C. [4]

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(c) Calculations

Working should be shown in all calculations.

[4.2 J are absorbed or released when the temperature of 1.0 cm3 of water changes by 1.0 °C.]

(i) Calculate the heat energy gained by the 50 cm3 of cold water in the 250 cm3

beaker.

The heat energy gained by the cold water = ………… J.

(ii) Calculate the heat energy lost by the 50 cm3 of hot water from the 100 cm3 beaker.

The heat energy lost by the hot water = ………… J.

(iii) The difference between the values calculated in (i) and (ii) is an approximate value for the total heat energy absorbed by the 250 cm3 beaker during the experiment. The heat capacity of the beaker is the amount of heat energy absorbed for a 1 °C change in temperature.

approximate heat capacityof the 250 cm3 beaker

= (heat energy lost) – (heat energy gained)(T3 – T2)

J °C–1

Use your answers to (i) and (ii) and the temperature rise from (b) to calculate the approximate heat capacity of the 250 cm3 beaker.

The approximate heat capacity of the 250 cm3 beaker = ………… J °C–1.

[1]

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(d) Determining the enthalpy change of solution for ammonium chloride

Follow the instructions below to find the temperature change when a known mass of solid ammonium chloride dissolves in water.

You are provided with two samples of ammonium chloride. You should use the sample labelled NH4Cl in experiment 1 and the sample labelled FA 1 in experiment 2.

Experiment 1 • Enter all results in the table below. • Weigh the stoppered tube containing ammonium chloride, which is labelled

NH4Cl. • Use the 50 cm3 measuring cylinder to transfer 100 cm3 of cold water into the rinsed

and dried 250 cm3 beaker used in (a). • Stir the water in the beaker with the thermometer and record the temperature. • Add the solid from the weighed tube to the water. • Stir the mixture constantly with the thermometer. • Record the minimum temperature obtained in the solution. • Reweigh the tube labelled NH4Cl, its stopper and any residual ammonium

chloride. • Empty and rinse the beaker and dry it using a paper towel.

Experiment 2 • Enter all results in the table below. • Weigh a clean, dry, boiling-tube. • Weigh between 9.8 g and 10.2 g of FA 1, ammonium chloride, into the boiling-tube. • Repeat the procedure in experiment 1 and record the minimum temperature

obtained when this mass of FA 1 dissolves in 100 cm3 of water. • Reweigh the boiling-tube and any residual ammonium chloride.

Results

experiment 1 experiment 2

mass of tube + ammonium chloride / g

mass of empty tube / g

mass of tube + residual ammonium chloride / g

mass of ammonium chloride / g

initial temperature of water / °C

minimum temperature obtained / °C

temperature fall, ΔT / oC

[6]

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(e) Calculations


(i) Use the temperature fall from (d), experiment 1, to calculate the change in heat energy of the solution.

[4.3 J are absorbed or released when the temperature of 1.0 cm3 of solution changes by 1.0 °C.]

The change in heat energy of the solution = ................. J.

(ii) To calculate the total change in heat energy as ammonium chloride dissolves in water, the change in heat energy of the 250 cm3 beaker has to be added to the change in heat energy of the solution.

Explain why these two changes in heat energy have to be added together.

..................................................................................................................................

..................................................................................................................................

..................................................................................................................................

(iii) Use your answer in (i) above and the approximate heat capacity of the 250 cm3 beaker calculated in (c)(iii) to calculate the combined change in heat energy of the beaker and solution.

The combined change in heat energy of the beaker and solution = ................. J.

(iv) Calculate how many moles of FA 1, NH4Cl, were used in (d), experiment 1. [Ar; Cl, 35.5; H, 1.0; N, 14.0]

………… mol of FA 1 were used in experiment 1.

i

ii

iii

iv

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(v) Calculate the enthalpy change when 1 mol of FA 1 dissolves in an excess of water.This is the molar enthalpy change of solution, ΔHsolution (NH4Cl ).

Make certain that your answer is given in kJ mol–1 and has the appropriate sign.

ΔHsolution (NH4Cl ) = ........ ............................ kJ mol–1.

sign calculated value

(vi) Explain the significance of the sign you have given in (v) and how it is related to your experimental results.

..................................................................................................................................

..................................................................................................................................

.................................................................................................................................. [8]

v

vi

vii

viii

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(f) Evaluation

A data book value for the molar enthalpy change of solution, ΔHsolution (NH4Cl ), is +15.2 kJ mol–1.

The value you have obtained may be significantly different from this value.

Calculate the difference between your value of ΔHsolution (NH4Cl ) and the data book value. Record this difference below. Express this difference as a percentage of the data book value.

difference = ……………….. kJ mol–1

percentage difference = ……………….. % [1]

(g) Sources of error

Describe one major source of error in this experiment. Suggest an improvement which would significantly increase the accuracy of the experiment. Explain why your suggestion would produce a more accurate value.

description of major source of error

.........................................................................................................................................

.........................................................................................................................................

suggested improvement

.........................................................................................................................................

.........................................................................................................................................

explanation of why suggestion would increase experimental accuracy

.........................................................................................................................................

......................................................................................................................................... [2]

[Total: 25]

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ForExaminer’s

Use

2 (a) You are provided with three solutions, FA 2, FA 3 and FA 4. The only anions that may be present in these solutions are sulfate and carbonate. One or more of the solutions may contain both anions.

Identification of the anions in FA 2, FA 3 and FA 4.

Most metal carbonates are insoluble, most metal sulfates are soluble and all metal nitrates are soluble in water.

(i) Use this information and the Qualitative Analysis Notes on page 16 to select • reagent 1, to identify any carbonate ion present, • reagent 2, to identify any sulfate ion present.

reagent 1 ............................................. reagent 2 ............................................. [1]

(ii) Explain the order in which you will add your chosen reagents to determine the anion or anions present in each of FA 2, FA 3 and FA 4.

..................................................................................................................................

..................................................................................................................................

..............................................................................................................................[1]

(iii) Use the reagents selected in (a)(i) to test each of the solutions FA 2, FA 3 and FA 4. Record your observations in the table below.

reagentobservations

FA 2 FA 3 FA 4

[2]

(iv) From your observations, identify the anion or anions present in each of the solutions.

solution carbonate sulfate evidence

FA 2

FA 3

FA 4

[2]

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13


ForExaminer’s

Use

(b

) Yo

u ar

e pr

ovid

ed w

ith fo

ur s

olut

ions

, FA

5, F

A 6

, FA

7 a

nd F

A 8

. Per

form

the

test

-tub

e ex

perim

ents

des

crib

ed b

elow

and

reco

rd y

our o

bser

vatio

ns

in th

e ta

ble.

Whe

re g

ases

are

rel

ease

d th

ey s

houl

d be

iden

tifie

d by

a te

st, d

escr

ibed

in t

he

app

rop

riat

e p

lace

in y

ou

r o

bse

rvat

ion

s.

test

sob

serv

atio

ns

FA 5

FA 6

FA 7

FA 8

(i)

To a

bout

1 c

m d

epth

of s

olut

ion

in a

test

-tub

e,

add

10 d

rops

of a

queo

us s

odiu

m h

ydro

xide

.S

hake

the

mix

ture

,

then

add

a fu

rthe

r 2

cm d

epth

of a

queo

us

sodi

um h

ydro

xide

.S

hake

the

mix

ture

aga

in,

then

leav

e th

e tu

be to

sta

nd fo

r 2–

3 m

inut

es.

(ii)

If no

pre

cipi

tate

has

form

ed in

test

(i)

abo

ve;

tran

sfer

the

solu

tion

to a

bo

ilin

g-t

ub

e an

d w

arm

gen

tly w

ith a

Bun

sen

burn

er.

Car

e: h

eati

ng

aq

ueo

us

sod

ium

hyd

roxi

de

in a

tu

be

may

cau

se t

he

solu

tio

n t

o b

e ej

ecte

d f

rom

th

e tu

be.

(iii)

To a

bout

1 c

m d

epth

of s

olut

ion

in a

test

-tub

e,

add

10 d

rops

of a

queo

us a

mm

onia

.S

hake

the

mix

ture

,

then

add

a fu

rthe

r 2

cm d

epth

of a

queo

us

amm

onia

.S

hake

the

mix

ture

aga

in,

then

leav

e th

e tu

be to

sta

nd fo

r 2–

3 m

inut

es.

[7

]

i

ii

iii

iv

v

vi

vii

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14

9701/33/M/J/10© UCLES 2010

ForExaminer’s

Use

(c) From your observations in (b), identify the cation present in each of the following solutions.

solution cation evidence

FA 5

FA 6

FA 8

[2]

[Total: 15]

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9701/33/M/J/10© UCLES 2010

Qualitative Analysis Notes



ionreaction with

NaOH(aq) NH3(aq)

aluminium,

Al 3+(aq)

white ppt.

soluble in excess

white ppt.

insoluble in excess

ammonium,

NH4+(aq)

no ppt.


barium,


calcium,





grey-green ppt.

insoluble in excess

copper(II),Cu2+(aq)

pale blue ppt.

insoluble in excess



iron(II),Fe2+(aq)


insoluble in excess


insoluble in excess

iron(III),Fe3+(aq)

red-brown ppt.

insoluble in excess

red-brown ppt.

insoluble in excess

lead(II),Pb2+(aq)

white ppt.

soluble in excess

white ppt.

insoluble in excess

magnesium,

Mg2+(aq)

white ppt.

insoluble in excess

white ppt.

insoluble in excess



insoluble in excess


insoluble in excess

zinc,

Zn2+(aq)

white ppt.

soluble in excess

white ppt.

soluble in excess


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16

9701/33/M/J/10© UCLES 2010




ion reaction

carbonate,

CO32–


chromate(VI),

CrO42– (aq)




chloride,

Cl– (aq)



bromide,

Br– (aq)



iodide,

I– (aq)



nitrate,

NO3– (aq)

NH3 liberated on heating with OH–(aq) and Al foil

nitrite,

NO2– (aq)

NH3 liberated on heating with OH–(aq) and Al foil;


sulfate,

SO42– (aq)

gives white ppt. with Ba2+(aq) (insoluble in excess dilute strong acid) or gives white ppt. with Pb2+(aq)

sulfite,

SO32– (aq)


gives white ppt. with Ba2+(aq) (soluble in excess dilute strong acid)

3 Tests for gases







sulfur dioxide, SO2 turns acidified aqueous potassium dichromate(VI) (aq) from orange to green

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DC (SJF5449/CGW) 11614/4© UCLES 2010 [Turn over

*1626130202*







CHEMISTRY 9701/34


2 hours




1

2

Total

Session

Laboratory

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9701/34/M/J/10© UCLES 2010

ForExaminer’s

Use

1 Read through question 1 before starting any practical work.

You are provided with the following reagents. • weighing bottles/tubes labelled FB 1, FB 2 and FB 3; each containing a different mass

of sodium hydrogencarbonate, NaHCO3 • additional solid sodium hydrogencarbonate (approximately 10 g) • FB 4, 3.0 mol dm–3 hydrochloric acid, HCl

The reaction of sodium hydrogencarbonate with hydrochloric acid is endothermic.

By measuring the maximum temperature decrease when the different masses of sodium hydrogencarbonate react with hydrochloric acid you are to determine the enthalpy change of neutralisation for 1 mol of NaHCO3 with HCl.

(a) Method

• Weigh the bottle/tube containing the sodium hydrogencarbonate labelled FB 1. • Support the plastic cup in the 250 cm3 beaker. • Use the measuring cylinder to transfer 30 cm3 of FB 4 into the plastic cup. • Place the thermometer in the acid in the plastic cup and record the steady

temperature of the acid. • Add the contents of the weighed tube, FB 1, to the acid in the plastic cup, a little at

a time with constant stirring. • You should add the solid as quickly as possible – taking care to minimise any acid

spray from the plastic cup. Avoid breathing any fumes from the experiment. • Record the minimum temperature obtained in the reaction. • Reweigh the emptied tube, FB 1, containing any remaining solid that was not tipped

from the tube. • Empty and rinse the plastic cup. Rinse the thermometer. Shake dry the plastic cup. • Repeat the experiment using tubes labelled FB 2 and FB 3. In each experiment

use 30 cm3 of FB 4.

Carry out two further experiments. Using the empty weighing bottles/tubes, labelled FB 5 and FB 6, weigh two further

masses of sodium hydrogencarbonate. Choose masses to enable you to plot an appropriate graph of temperature change against mass of sodium hydrogencarbonate.

Results Record your results in an appropriate form showing, for each experiment, the

measurements of mass and temperature and the calculated temperature fall.

[9]

i

ii

iii

iv

v

vi

vii

viii

ix

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3


ForExaminer’s

Use

(b) Use the grid below to plot a graph of decrease in temperature (y-axis) against the mass of sodium hydrogencarbonate added (x-axis).

Draw a line of best fit through the plotted points. You should consider if the best-fit line passes through the origin (0,0) of the graph.

[4]

i

ii

iii

iv

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9701/34/M/J/10© UCLES 2010

ForExaminer’s

Use

(c) Explain why the mass of NaHCO3 is plotted on the x-axis rather than on the y-axis.

.........................................................................................................................................

..................................................................................................................................... [1]

(d) Construct the balanced equation for the reaction of NaHCO3 with hydrochloric acid.

..................................................................................................................................... [1]

(e) Calculate the gradient of your graph. Show all of your working clearly, both construction lines on the graph and working in the

calculation.

[3]

(f) Although there is insufficient acid in 30 cm3 of FB 4 to neutralise 1 mol of NaHCO3 it is possible to calculate the theoretical fall in temperature for this reaction.

Use your answer from (e) to calculate this value. [Ar: C, 12.0; H, 1.0; Na, 23.0; O, 16.0]

The theoretical fall in temperature for 1 mol of NaHCO3 = ………………………. °C [1]

(g) Calculate the theoretical enthalpy change for the neutralisation of 1 mol of NaHCO3 by hydrochloric acid. Give your answer in kJ mol–1 and include the correct sign for the reaction.

[4.3 J are absorbed or released when the temperature of 1 cm3 of solution changes by 1 °C.]

ΔH = ……………………… kJ mol–1 [2]

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ForExaminer’s

Use

(h) Suggest two ways in which your apparatus could be modified to reduce transfer of heat from the surroundings to the solution in the apparatus.

modification 1 ..................................................................................................................

.........................................................................................................................................

modification 2 ..................................................................................................................

..................................................................................................................................... [1]

(i) State and explain why the experiment would be more accurate if the volumes of FB 4 had been measured using a burette instead of a measuring cylinder.

.........................................................................................................................................

..................................................................................................................................... [1]

(j) The mass of NaHCO3 used in a further experiment and its associated temperature change are shown in the tables below.

• The mass was obtained on a balance reading to 1 decimal place. • The thermometer used was graduated at 1 °C.

Complete the table to show the errors in these results.

mass of NaHCO3 5.6 g temperature change –12.0 °C

maximum error in a single balance reading ± ………… g

maximum error in a single thermometer reading ± ………… °C

% error in measured mass ………… %

% error in temperature change ………… %

[2]

(k) Two students add 6.0 g of sodium carbonate to 50.00 cm3 of 2.0 mol dm–3 hydrochloric acid. Each student repeats the experiment a number of times.

The thermometer readings and temperature changes obtained consistently by each student are shown below.

initial temperature / °C

final temperature / °C

temperature rise/ °C

student 1 20.0 28.0 8.0

student 2 19.0 27.0 8.0

Suggest the type of error shown by these results.

..................................................................................................................................... [1]

[Total: 26]

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9701/34/M/J/10© UCLES 2010

ForExaminer’s

Use

2 FB 7 and FB 8 are aqueous solutions of salts. One of these contains two cations and one anion.

The other contains one cation and one anion. Both FB 7 and FB 8 have a common cation.

You will carry out tests to deduce the following. • the cations present in each solution • whether a sulfate ion is present in either solution

At each stage of any test you are to record details of the following. • colour changes seen • the formation of any precipitate and the colour of the precipitate

Where gases are released they should be identified by a test, described in the appropriate place in your observations.

You should indicate clearly at what stage in a test a change occurs. Marks are not given for chemical equations. No additional tests for ions present should be attempted. If any solution is warmed directly with a Bunsen burner a boiling-tube MUST be used.

Rinse and reuse test-tubes where possible.

(a) Use information from the Qualitative Analysis Notes on page 11 to select a pair of reagents that, used together, determine whether a sulfate ion is present in either solution.

The reagents are …………………………………………

followed by ………………………………………… . [1]

(b) Use your chosen reagents to carry out tests on FB 7 and FB 8. Record your results in an appropriate form in the space below.

[2]

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ForExaminer’s

Use

(c) From your observations in (b) show with a tick which of the following statements is true.

FB 7 contains the sulfate ion

FB 8 contains the sulfate ion

neither solution contains the sulfate ion

Explain the evidence that supports your conclusion.

.........................................................................................................................................

..................................................................................................................................... [1]

(d) Carry out the following tests on the solutions FB 7 and FB 8. Record your observations below.

test observations

FB 7 FB 8

To 1 cm depth of solution in a boiling-tube, add 2 cm depth of aqueous sodium hydroxide;then

warm the solution gently.

Care is needed when heating aqueous sodium hydroxide.

To 1 cm depth of solution in a test-tube, add 2 cm depth of aqueous ammonia.

[3]

(e) To 1 cm depth of FB 7 in a test-tube add 1 cm depth of sodium hydroxide. Leave to stand for a few minutes.

observation

.........................................................................................................................................

..................................................................................................................................... [1]

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9701/34/M/J/10© UCLES 2010

ForExaminer’s

Use

(f) From your observations in (d) and (e) you should be able to identify the common cation in the solutions and the second cation in one of the solutions.

The common cation present in both solutions is ………………………. .

The second cation contained in one of the solutions is ………………………. .

Explain how your observations support your conclusions for

(i) the common cation,

.................................................................................................................................

.................................................................................................................................

(ii) the second cation.

.................................................................................................................................

................................................................................................................................. [1]

Read through the remainder of question 2 before starting further practical work. Heat a half-full 250 cm3 beaker of water for use as a hot water-bath.

(g) FB 9, FB 10, FB 11 and FB 12 are organic compounds. Each contains one of the following different functional groups.

• primary alcohol • secondary alcohol • aldehyde • ketone

You are to react each of these compounds with some of the following reagents. • acidified aqueous potassium dichromate(VI) • 2,4-dinitrophenylhydrazine (2,4-DNPH) reagent • ammoniacal silver nitrate (Tollens’ reagent)

You are provided with the first two reagents. You must prepare the last of these reagents, Tollens’ reagent, immediately before use. Follow the instructions in the box below.

To 2 cm depth of aqueous silver nitrate in a boiling-tube add ½ cm depth of aqueous sodium hydroxide. This will produce a brown precipitate of silver(I) oxide. Add aqueous ammonia a little at a time, with continuous shaking, until the brown precipitate just dissolves. Do not add an excess of aqueous ammonia.

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9

9701/34/M/J/10© UCLES 2010

ForExaminer’s

Use

In each of the following tests add a few drops of the reagent to 1 cm depth of FB 9, FB 10, FB 11 and FB 12 in separate test-tubes.

In the tests using acidified potassium dichromate(VI) and Tollens’ reagent, if no initial reaction is seen, warm that tube and its contents in your hot water-bath. There is no need to heat any tube to which you have added 2,4-DNPH reagent.

Do not heat any tube with a naked flame.

Record your results in the table below.

Do not carry out tests for the shaded boxes.

reagentobservations

FB 9 FB 10 FB 11 FB 12

acidified potassium dichromate(VI)

2,4-DNPH reagent

Tollens’ reagent

[3]

(h) State which of the solutions contain alcohols. Explain the observations leading to your conclusion.

FB …………… and FB …………… contain alcohols.

explanation .....................................................................................................................

.........................................................................................................................................

State which solution contains the ketone. Explain the observations leading to your conclusion.

FB …………… contains the ketone.

explanation .....................................................................................................................

......................................................................................................................................... [2]

[Total: 14]

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9701/34/M/J/10© UCLES 2010



ionreaction with

NaOH(aq) NH3(aq)

aluminium,

Al 3+(aq)

white ppt.

soluble in excess

white ppt.

insoluble in excess

ammonium,

NH4+(aq)

no ppt.


barium,


calcium,





grey-green ppt.

insoluble in excess

copper(II),Cu2+(aq)

pale blue ppt.

insoluble in excess



iron(II),Fe2+(aq)


insoluble in excess


insoluble in excess

iron(III),Fe3+(aq)

red-brown ppt.

insoluble in excess

red-brown ppt.

insoluble in excess

lead(II),Pb2+(aq)

white ppt.

soluble in excess

white ppt.

insoluble in excess

magnesium,

Mg2+(aq)

white ppt.

insoluble in excess

white ppt.

insoluble in excess



insoluble in excess


insoluble in excess

zinc,

Zn2+(aq)

white ppt.

soluble in excess

white ppt.

soluble in excess


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11

9701/34/M/J/10© UCLES 2010


ion reaction

carbonate,

CO32–


chromate(VI),

CrO42– (aq)




chloride,

Cl– (aq)



bromide,

Br– (aq)



iodide,

I– (aq)



nitrate,

NO3– (aq)

NH3 liberated on heating with OH-(aq) and Al foil

nitrite,

NO2– (aq)

NH3 liberated on heating with OH-(aq) and Al foil;


sulfate,

SO42– (aq)

gives white ppt. with Ba2+(aq) or with Pb2+(aq) (insoluble in excess dilute strong acids);

sulfite,

SO32– (aq)


gives white ppt. with Ba2+(aq) (soluble in excess dilute strong acids)

3 Tests for gases







sulfur dioxide, SO2 turns acidified aqueous potassium dichromate(VI) from orange to green

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9701/34/M/J/10© UCLES 2010

BLANK PAGE



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DC (LEO/SW) 23108/2© UCLES 2010 [Turn over

*5803539249*







CHEMISTRY 9701/35


2 hours




1

2

Total

Session

Laboratory

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2

9701/35/M/J/10© UCLES 2010

BLANK PAGE

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3


ForExaminer’s

Use

1 You are required to find the molar enthalpy change for the decomposition of sodium hydrogencarbonate, NaHCO3.

NaHCO3 ½Na2CO3 + ½H2O + ½CO2

FA 1 is anhydrous sodium hydrogencarbonate. FA 2 is anhydrous sodium carbonate. FA 3 is 4.0 mol dm–3 hydrochloric acid.

You will determine the value for the molar enthalpy change of neutralisation for each of FA 1 and FA 2, using an excess of FA 3. You will then use these values to calculate the molar enthalpy change for the decomposition of sodium hydrogencarbonate.

Warning: 4.0 mol dm–3 hydrochloric acid is an irritant. Very rapid effervescence occurs when FA 1 or FA 2 are added to FA 3.

For safe working, and to minimize the formation of ‘acid mist’, the solid must be added carefully, with stirring, to the acid. See further instructions below.

Before starting any practical work read through the instructions in (a) and draw up two tables to record your results.

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9701/35/M/J/10© UCLES 2010

ForExaminer’s

Use

(a) Determining the molar enthalpy change of neutralisation between FA 1 and FA 3

NaHCO3 + HCl NaCl + H2O + CO2

Follow the instructions below to determine the temperature change when a known mass of FA 1, sodium hydrogencarbonate, reacts with an excess of FA 3, hydrochloric acid.

• Weigh the stoppered tube labelled FA 1 containing sodium hydrogencarbonate. • Use a 50 cm3 measuring cylinder to transfer 50 cm3 of FA 3 into a 250 cm3 beaker. • Stir the acid in the beaker with the thermometer. Record the temperature of the

acid; this is the temperature at t = 0 min. • Record the temperature each minute for 3 minutes. • At t = 4 min, start to carefully add the weighed sample of FA 1 to the acid. • Add the solid in at least 4 or 5 portions to prevent excessive effervescence. • While adding the solid stir the mixture constantly with the thermometer, but do not

record the temperature. • Continue to stir the mixture throughout the experiment. • Record the temperature at t = 5 min, then every ½ minute until t = 8 min. • Reweigh the tube labelled FA 1, its stopper and any residual sodium

hydrogencarbonate. • Empty and rinse the beaker and dry it using a paper towel. • In one of your tables record the balance readings and the mass of FA 1 added;

in the second table record all measurements of time and temperature.

Table of results

[3]

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5


ForExaminer’s

Use

(b) Graph plotting

1. Plot a graph of temperature (y-axis) against time (x-axis) on the grid below. 2. Draw two straight lines of best fit; one through the points up to t = 3 min; the second

through the points from t = 5 min to t = 8 min. Extrapolate both lines to t = 4 min. 3. From the extrapolated lines read the minimum and the maximum temperatures at

t = 4 min. Record these values in the spaces provided below. 4. Determine the value for the temperature fall at t = 4 min.

The minimum temperature at t = 4 min is …………. °C.

The maximum temperature at t = 4 min is ………… °C.

The temperature fall, ΔT1, at t = 4 min is ………… °C. [4]

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6

9701/35/M/J/10© UCLES 2010

ForExaminer’s

Use

(c) Calculations


(i) Use the equation below and the temperature fall, ΔT1, from (b) to calculate the change in heat energy during the reaction of FA 1 with FA 3.

change in heat energy = 50 × 4.3 × ΔT1

The change in heat energy = .................. J.

(ii) Calculate how many moles of FA 1, NaHCO3, were used in your experiment. [Ar; C, 12.0; H, 1.0; O, 16.0; Na, 23.0]

.................. mol of FA 1 were used in the experiment.

(iii) Calculate the enthalpy change when 1 mol of FA 1 reacts with an excess of the hydrochloric acid, FA 3.

This is the molar enthalpy change of neutralisation, ΔHneutralisation (NaHCO3). Make certain that your answer is given in kJ mol–1 and has the appropriate sign.

ΔHneutralisation(NaHCO3) = ........ ............................ kJ mol–1.


(iv) Explain the significance of the sign you have given in (iii) and how it is related to your experimental results.

..................................................................................................................................

..................................................................................................................................

.................................................................................................................................. [3]

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ForExaminer’s

Use

(d) Determining the molar enthalpy change of neutralisation between FA 2 and FA 3

Na2CO3 + 2HCl 2NaCl + H2O + CO2

Follow the instructions below to find the temperature change when a known mass of FA 2, sodium carbonate, reacts with an excess of FA 3, hydrochloric acid.

You are provided with two samples of sodium carbonate. You should use the sample labelled Na2CO3 in experiment 1 and the sample labelled FA 2 in experiment 2.

Experiment 1 • Enter all results in the table below. • Weigh the stoppered tube containing sodium carbonate, which is labelled Na2CO3. • Use a 50 cm3 measuring cylinder to transfer 50 cm3 of FA 3 into the rinsed and

dried 250 cm3 beaker used in (a). • Stir the acid in the beaker with the thermometer and record the temperature. • Start to add carefully the weighed sample of Na2CO3 to the acid. • As in the experiment in (a), add the solid in at least 4 or 5 portions to prevent

excessive effervescence. • While adding the solid stir the mixture constantly with the thermometer. • Record the maximum temperature obtained during the reaction. • Reweigh the tube labelled Na2CO3, its stopper and any residual sodium

carbonate. • Empty and rinse the beaker and dry it using a paper towel.

Experiment 2 • Enter all results in the table below. • Weigh a clean, dry, boiling-tube. • Weigh between 7.0 g and 7.5 g of FA 2, sodium carbonate, into the boiling-tube. • Repeat the procedure in experiment 1 and record the maximum temperature

obtained when this mass of FA 2 reacts with 50 cm3 of FA 3. • Reweigh the boiling-tube and any residual sodium carbonate.

Results

experiment 1 experiment 2

mass of tube + anhydrous sodium carbonate / g

mass of empty tube / g

mass of tube + residual sodium carbonate / g

mass of anhydrous sodium carbonate / g

initial temperature of acid / oC

maximum temperature obtained / oC

temperature rise, ΔT2 / oC

[6]

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9


ForExaminer’s

Use

(e) Calculations


(i) Use the equation below and the temperature rise, ΔT2, from (d) for experiment 1 to calculate the change in heat energy during the reaction of sodium carbonate with FA 3.

change in heat energy = 50 × 4.3 × ΔT2

Change in heat energy = .................. J.

(ii) Calculate how many moles of sodium carbonate were used in your experiment 1. [Ar; C, 12.0; O, 16.0; Na, 23.0]

.................. mol of sodium carbonate were used in experiment 1.

(iii) Calculate the enthalpy change when 1 mol of sodium carbonate reacts with an excess of the hydrochloric acid, FA 3.

This is the molar enthalpy change of reaction, ΔHneutralisation(Na2CO3). Make certain that your answer is given in kJ mol–1 and has the appropriate sign.

ΔHneutralisation(Na2CO3) = ........ ............................ kJ mol–1.


(iv) Explain the significance of the sign you have given in (iii) and how it is related to your experimental results.

..................................................................................................................................

..................................................................................................................................

.................................................................................................................................. [5]

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10

9701/35/M/J/10© UCLES 2010

ForExaminer’s

Use

(f) Calculating the enthalpy change of decomposition of FA 1, ΔHdecomposition(NaHCO3)

Use your values for ΔHneutralisation (NaHCO3) and ΔHneutralisation (Na2CO3) in the expression below to calculate a value for the molar enthalpy change of decomposition, ΔH decomposition (NaHCO3), for FA 1.

ΔH decomposition (NaHCO3) = ΔHneutralisation (NaHCO3) – ½ΔHneutralisation (Na2CO3)

ΔHdecomposition(NaHCO3) = ........ ............................ kJ mol–1.

sign calculated value [1]

(g) Evaluation

An alternative method for the determination of ΔHdecomposition (NaHCO3) gave a value of +42.5 kJ mol–1.

The value you have obtained may be significantly different from this value.

Calculate the difference between your value of ΔHdecomposition (NaHCO3) and that obtained by the alternative method.

Record this difference below. Express this difference as a percentage of the alternative value.

difference = ………………. kJ mol–1

percentage difference = ……………….. % [1]

(h) Sources of error

Describe one major source of error in this experiment. Suggest an improvement which would significantly increase the accuracy of the experiment. Explain why your suggestion would produce a more accurate value.

description of major source of error

.........................................................................................................................................

.........................................................................................................................................

suggested improvement

.........................................................................................................................................

.........................................................................................................................................

explanation of why suggestion would increase experimental accuracy

.........................................................................................................................................

......................................................................................................................................... [2]

[Total: 25]

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11


ForExaminer’s

Use

2 (a) You are provided with three solutions, FA 4, FA 5 and FA 6. The only anions that may be present in these solutions are carbonate and chloride. One or more of the solutions may contain both anions.

Identification of the anions in FA 4, FA 5 and FA 6

Most metal carbonates are insoluble, most metal chlorides are soluble and all metal nitrates are soluble in water.

(i) Use this information and the Qualitative Analysis Notes on page 15 to select • reagent 1, to identify any carbonate ion that is present, • reagent 2, to identify any chloride ion present.

reagent 1 ............................................. reagent 2 ............................................. [1]

(ii) Explain the order in which you will add your chosen reagents to determine the anion or anions present in each of FA 4, FA 5 and FA 6.

..................................................................................................................................

..................................................................................................................................

............................................................................................................................. [1]

(iii) Use the reagents selected in (a)(i) to test each of the solutions FA 4, FA 5 and FA 6. Record your observations in the table below.

reagentobservations

FA 4 FA 5 FA 6

[2]

(iv) From your observations, identify the anion or anions present in each of the solutions.

solution carbonate chloride evidence

FA 4

FA 5

FA 6

[2]

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ForExaminer’s

Use

(b

) Yo

u ar

e pr

ovid

ed w

ith f

our

solu

tions

, FA

7,

FA 8

, FA

9 a

nd F

A 1

0. P

erfo

rm t

he t

est-

tube

exp

erim

ents

des

crib

ed b

elow

and

rec

ord

your

ob

serv

atio

ns in

the

tabl

e.

test

sob

serv

atio

ns

FA 7

FA 8

FA 9

FA 1

0

(i)

To a

bout

1 c

m d

epth

of s

olut

ion

in a

te

st-t

ube,

add

5 d

rops

of a

queo

us s

odiu

m

hydr

oxid

e, s

hake

the

mix

ture

then

,

add

a fu

rthe

r 2

cm d

epth

of a

queo

us

sodi

um h

ydro

xide

.

(ii)

To a

bout

1 c

m d

epth

of s

olut

ion

in a

te

st-t

ube,

add

10

drop

s of

aqu

eous

am

mon

ia, s

hake

the

mix

ture

then

,

add

a fu

rthe

r 2

cm d

epth

of a

queo

us

amm

onia

.

(iii)

Sel

ect a

rea

gent

that

will

con

firm

the

iden

tity

of a

ny io

ns p

rodu

cing

whi

te p

reci

pita

tes

in b

oth

of th

e te

sts

abov

e.To

abo

ut 1

cm

dep

th o

f sol

utio

n in

a te

st-t

ube

add

the

sele

cted

rea

gent

. Rec

ord

the

appr

opria

te o

bser

vatio

ns b

elow

.

Th

e re

agen

t is

[7

]

i

ii

iii

iv

v

vi

vii

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(c) From your observations, identify the cation present in each of the following solutions.

solution cation evidence

FA 7

FA 9

FA 10

[2]

[Total: 15]

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9701/35/M/J/10© UCLES 2010

Qualitative Analysis Notes



ionreaction with

NaOH(aq) NH3(aq)

aluminium,

Al 3+(aq)

white ppt.

soluble in excess

white ppt.

insoluble in excess

ammonium,

NH4+(aq)

no ppt.


barium,


calcium,





grey-green ppt.

insoluble in excess

copper(II),Cu2+(aq)

pale blue ppt.

insoluble in excess



iron(II),Fe2+(aq)


insoluble in excess


insoluble in excess

iron(III),Fe3+(aq)

red-brown ppt.

insoluble in excess

red-brown ppt.

insoluble in excess

lead(II),Pb2+(aq)

white ppt.

soluble in excess

white ppt.

insoluble in excess

magnesium,

Mg2+(aq)

white ppt.

insoluble in excess

white ppt.

insoluble in excess



insoluble in excess


insoluble in excess

zinc,

Zn2+(aq)

white ppt.

soluble in excess

white ppt.

soluble in excess


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9701/35/M/J/10© UCLES 2010


ion reaction

carbonate,

CO32–


chromate(VI),

CrO42– (aq)




chloride,

Cl– (aq)



bromide,

Br– (aq)



iodide,

I– (aq)



nitrate,

NO3– (aq)

NH3 liberated on heating with OH–(aq) and Al foil

nitrite,

NO2– (aq)

NH3 liberated on heating with OH–(aq) and Al foil;


sulfate,

SO42– (aq)

gives white ppt. with Ba2+(aq) (insoluble in excess dilute strong acid) or gives white ppt. with Pb2+(aq)

sulfite,

SO32– (aq)


gives white ppt. with Ba2+(aq) (soluble in excess dilute strong acid)

3 Tests for gases







sulfur dioxide, SO2 turns acidified aqueous potassium dichromate(VI) (aq) from orange to green

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DC (CW/DJ) 25442/4© UCLES 2010 [Turn over

UNIVERSITY OF CAMBRIDGE INTERNATIONAL EXAMINATIONSGeneral Certificate of Education Advanced Level


Write your Centre number, candidate number and name on all the work you hand in.Write in dark blue or black pen.You may use a pencil for any diagrams, graphs or rough working.Do not use staples, paper clips, highlighters, glue or correction fluid.DO NOT WRITE IN ANY BARCODES.

Section AAnswer all questions.

Section BAnswer all questions.

You may lose marks if you do not show your working or if you do not use appropriate units.A Data Booklet is provided.

At the end of the examination, fasten all your work securely together.The number of marks is given in brackets [ ] at the end of each question or part question.

*8342870404*

CHEMISTRY 9701/41

Paper 4 Structured Questions May/June 2010

1 hour 45 minutes




1

2

3

4

5

6

7

8

9

10

Total

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Section A

Answer all questions in the spaces provided.

1 (a) Phosphorus and sulfur are two non-metallic elements on the right hand side of the Periodic Table.

For each of these elements describe the observations you would make when it burns in air, and write a balanced equation for the reaction.

phosphorus

observation ......................................................................................................................

equation ...........................................................................................................................

sulfur

observation ......................................................................................................................

equation ........................................................................................................................... [4]

(b) White phosphorus, P4, is produced commercially by heating calcium phosphate(V) rock with a mixture of silica, SiO2, and coke in an electric furnace at 1400 °C. Calcium silicate, CaSiO3, and carbon monoxide are the other products.

(i) Balance the following equation which represents the overall process.

___ Ca3(PO4)2 + ___ SiO2 + ___ C ___ P4 + ___ CaSiO3 + ___ CO

When heated to 400 °C in the absence of air, white phosphorus is changed into the red form of the element. The following table lists some of the properties of the two forms, which are known as allotropes.

allotropeelectrical

conductivitymelting point

/ °Csolubility in

watersolubility in benzene

white none 44 insoluble soluble

red none 500 insoluble insoluble

(ii) Suggest the type of structure and bonding in each allotrope.

allotrope type of structure type of bonding

white

red

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(iii) In both allotropes, phosphorus has a valency of 3. Suggest by means of diagrams how the phosphorus atoms might be joined together in each allotrope.

white phosphorus

red phosphorus

[7]

[Total: 11]

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2 (a) Describe three characteristic chemical properties of transition elements that are not shown by Group II elements.

..........................................................................................................................................

..........................................................................................................................................

...................................................................................................................................... [3]

(b) When NH3(aq) is added to a green solution containing Ni2+(aq) ions, a grey-green precipitate is formed. This precipitate dissolves in an excess of NH3(aq) to give a blue-violet solution.

Suggest an explanation for these observations, showing your reasoning and including equations for the reactions you describe.

..........................................................................................................................................

..........................................................................................................................................

..........................................................................................................................................

..........................................................................................................................................

..........................................................................................................................................

...................................................................................................................................... [4]

(c) Dimethylglyoxime, DMG, is a useful reagent for the quantitative estimation of nickel. It forms an insoluble salt with nickel ions according to the following equation.

Ni2+(aq) + C4H8N2O2 NiC4H6N2O2(s) + 2H+(aq) DMG Ni-DMG

A small coin of mass 3.40 g was dissolved in nitric acid and an excess of DMG was added. The precipitated Ni-DMG was filtered off, washed and dried. Its mass was 4.00 g.

Calculate the % of nickel in the coin.

percentage of nickel = ..................................% [3]

[Total: 10]

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3 (a) Describe how the behaviour of the oxides of tin and lead in their +4 oxidation states differ on heating.

..........................................................................................................................................

...................................................................................................................................... [1]

(b) Explain the following by using data from the Data Booklet where appropriate, and writing equations for all reactions.

(i) A sample of liquid PbCl4 is placed in a flask and the flask is gently warmed. A gas is evolved and a white solid is produced. When the gas is bubbled through KI(aq), purple fumes are produced.

..................................................................................................................................

..................................................................................................................................

..................................................................................................................................

..................................................................................................................................

(ii) Repeating the same experiment using liquid SnCl4 instead of PbCl4 results in no evolution of gas, and no reaction with KI(aq).

..................................................................................................................................

..................................................................................................................................[4]

(c) The molecule dichlorocarbene, CCl2, can be produced under certain conditions. It is highly unstable, reacting with water to produce carbon monoxide and a strongly acidic solution.

(i) Suggest the electron arrangement in CCl2 and draw a dot-and-cross diagram showing this. Predict the shape of the molecule.

(ii) Construct an equation for the reaction of CCl2 with water.

..................................................................................................................................[3]

[Total: 8]

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4 Ethanolamine and phenylamine are two organic bases that are industrially important. Ethanolamine is a useful solvent with basic properties, whilst phenylamine is an important starting material in the manufacture of dyes and pharmaceuticals.

The following table lists some of their properties, together with those of propylamine.

compound formula Mr boiling point/ °C solubility in water

propylamine CH3CH2CH2NH2 59 48 fairly soluble

ethanolamine HOCH2CH2NH2 61 170 very soluble

phenylamine NH2 93 184

sparingly soluble

(a) Suggest why the boiling point of ethanolamine is much higher than that of propylamine. Draw a diagram to illustrate your answer.

..........................................................................................................................................

..........................................................................................................................................

[2]

(b) Describe and explain the relative basicities of propylamine and phenylamine.

..........................................................................................................................................

..........................................................................................................................................

...................................................................................................................................... [2]

(c) Write an equation showing ethanolamine acting as a Brønsted-Lowry base.

...................................................................................................................................... [1]

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(d) Propylamine can be synthesised from bromoethane by the following route.

CH3CH2Br CH3CH2CH2NH2

step 1

X

step 2

(i) Draw the structure of the intermediate compound X in the box above.

(ii) Suggest reagents and conditions for

step 1 ........................................................................................................................

step 2 ........................................................................................................................ [3]

(e) Apart from their relative basicities, ethanolamine and phenylamine differ in many of their reactions.

For each of these two compounds, describe one test that would give a positive result with the stated compound, but a negative result with the other.

ethanolamine

test ...................................................................................................................................

observation ......................................................................................................................

phenylamine

test ...................................................................................................................................

observation ...................................................................................................................... [4]

[Total: 12]

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Use

5 Although standard electrode potentials are measured for solutions where the concentrations of ions are 1.0 mol dm–3, cells used as sources of battery power tend to operate with more concentrated solutions. This question concerns the electrode reactions involved in the hydrogen-oxygen fuel cell and the lead-acid car battery.

(a) In the hydrogen-oxygen fuel cell, H2(g) and O2(g) are fed onto two inert electrodes dipping into NaOH(aq).

V

hydrogenoxygen

NaOH(aq)

The following reactions take place.

left hand electrode (cathode): H2(g) + 2OH–(aq) 2H2O(l) + 2e–

right hand electrode (anode): O2(g) + 2H2O(l) + 4e– 4OH–(aq)

(i) Use the Data Booklet to calculate E o––cell for this reaction.

..................................................................................................................................

(ii) Construct an equation for the overall reaction.

..................................................................................................................................

(iii) By using one of the phrases more positive, more negative or no change, deduce the effect of increasing [OH–(aq)] on the electrode potential of

• the left hand electrode .......................................................................

• the right hand electrode .......................................................................

(iv) Hence deduce whether the overall Ecell is likely to increase, decrease or remain the same, when [OH–(aq)] increases. Explain your answer.

..................................................................................................................................

..................................................................................................................................

(v) Suggest one other reason why a high [NaOH(aq)] is used in the fuel cell.

..................................................................................................................................[6]

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(b) In the cells of a lead-acid car battery the following reactions take place.

cathode: Pb(s) Pb2+(aq) + 2e–

anode: PbO2(s) + 4H+(aq) + 2e– Pb2+(aq) + 2H2O(l)

(i) Use the Data Booklet to calculate E o––cell for this reaction.

..................................................................................................................................

(ii) Construct an equation for the overall reaction.

..................................................................................................................................

The electrolyte in a lead-acid cell is H2SO4(aq). Most of the Pb2+(aq) ions that are produced at the electrodes are precipitated as the highly insoluble PbSO4(s).

(iii) Construct an equation for the overall cell reaction in the presence of H2SO4.

..................................................................................................................................

(iv) By considering the effect of decreasing [Pb2+(aq)] on the electrode potentials of the cathode and the anode, deduce the effect of the presence of H2SO4(aq) in the electrolyte on the overall Ecell.

State whether the Ecell will increase, decrease or remain the same. Overall Ecell will ................................................ .

Explain your answer.

..................................................................................................................................

..................................................................................................................................[5]

[Total: 11]

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Use

6 Acyl chlorides are useful intermediates in organic syntheses.

(a) (i) State a suitable reagent for converting carboxylic acids into acyl chlorides.

..................................................................................................................................

(ii) Construct an equation for the reaction between ethanoic acid, CH3CO2H, and the reagent you have stated in (i).

..................................................................................................................................[2]

(b) (i) In the boxes provided draw the structures of the compounds formed when benzoyl chloride undergoes the following reactions.

C2H5OH

COCl

I II

A

NH3

B

(ii) Name the functional group in

• compound A ..................................................................

• compound B ................................................................. .

(iii) What type of reaction is reaction II?

..................................................................................................................................[5]

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(c) (i) Suggest suitable acyl chlorides to use in the following reaction. Draw their structures in the boxes provided.

+ H2NNH2

NHHN

O O

OH

OHO

O

C E

O

O On

+

D F

Compound E dissolves in, but does not react with, cold water.

(ii) Suggest the major type of intermolecular interaction that occurs between E and water.

..................................................................................................................................

(iii) A solution of the diamine H2NCH2CH2NH2 in water has pH = 11 but a solution of E in water has pH = 7. Suggest why this is the case.

..................................................................................................................................

..................................................................................................................................

(iv) What type of polymer is compound F?

..................................................................................................................................[5]

[Total: 12]

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ForExaminer’s

Use

7 Predict the products of the following reactions and draw their structures in the boxes provided. Note that the molecular formula of the final product is given in each case.

Cl2 + light

C8H10O

NaOH

heat

Cl2 + AlCl3

C8H8ClO2N

HNO3 +

H2SO4

55˚C

KMnO4

+ OH–

+ heat

then H+

C10H10O4

CH3OH +conc. H2SO4

heat

[6]

[Total: 6]

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ForExaminer’s

Use

Section B


8 The molecule that contains the genetic information for an individual organism is called deoxyribonucleic acid, DNA.

(a) The diagram shows part of a DNA molecule. Study the diagram and identify the blocks labelled J, K, L and M as accurately as you can.

J cytosine K

adenine M

L

block letter identity

J

K

L

M [3]

(b) The DNA molecule is formed from two polymer strands. What stops these strands from separating from each other?

..........................................................................................................................................

...................................................................................................................................... [2]

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ForExaminer’s

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(c) List three differences between the structures of DNA and RNA.

1. ......................................................................................................................................

..........................................................................................................................................

..........................................................................................................................................

2. ......................................................................................................................................

..........................................................................................................................................

..........................................................................................................................................

3. ......................................................................................................................................

..........................................................................................................................................

.......................................................................................................................................... [3]

(d) Outline the different roles of mRNA and tRNA in the processes of transcription and translation.

mRNA ..............................................................................................................................

..........................................................................................................................................

..........................................................................................................................................

tRNA ................................................................................................................................

..........................................................................................................................................

.......................................................................................................................................... [2]

[Total: 10]

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ForExaminer’s

Use

9 A range of modern analytical techniques has made the identification of molecules, and atoms in compounds, much more rapid than traditional laboratory analysis.

(a) One instrumental technique is NMR spectroscopy, which uses the fact that under certain conditions protons can exist in two different energy states.

Explain how these different energy states arise.

..........................................................................................................................................

..........................................................................................................................................

...................................................................................................................................... [2]

(b) When methanol, CH3OH, is examined using NMR spectroscopy, it absorbs at two different frequencies. Explain why, and predict the relative areas of the two peaks.

..........................................................................................................................................

..........................................................................................................................................

...................................................................................................................................... [2]

(c) The NMR spectrum below is that of one of three possible isomers of molecular formula C3H6O2.

10 9 8 7 6 5chemical shift, δ / ppm

A B

4 3 2 1 0

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The compound could be propanoic acid, methyl ethanoate or ethyl methanoate.

(i) In the boxes provided, draw the structures of the three compounds.

propanoic acid methyl ethanoate ethyl methanoate

(ii) Explain which compound produced the spectrum shown, indicating which protons are responsible for each of the peaks A and B.

..................................................................................................................................

..................................................................................................................................

..................................................................................................................................

(iii) The NMR spectrum of another of the compounds has a peak at δ11.0. State which compound this would be, and identify the proton(s) responsible for this

peak.

compound ..................................................

proton(s) .................................................. [4]

(d) X-ray crystallography is a technique used to identify the relative positions of atoms in a crystal of a compound.

(i) What further information about organic macromolecules can be deduced by the use of X-ray crystallography?

..................................................................................................................................

..................................................................................................................................

(ii) Which atoms cannot be located by X-ray crystallography?

........................................................ [2]

[Total: 10]

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10 The nature and variety of drugs that are available to treat diseases or life-threatening conditions has never been greater. At the same time, we are much better able to deliver drugs to their targets in the body.

(a) Some drugs have to be given by injection, rather than by mouth. Name a functional group in a drug molecule that might be broken down by the acid in

the stomach.

...................................................................................................................................... [1]

(b) The anti-cancer drug Taxol could be broken down if taken by mouth.

O

O O

O

O

O

O

O

O

O

OH

O

NH

HO

OHH

Taxol

Circle two bonds, each in a different functional group, that could be hydrolysed in the digestive system. [2]

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(c) One way of protecting drug molecules that are taken by mouth is to enclose them in liposomes. These are artificially created spheres made from phospholipids which have an ionic phosphate ‘head’ and two hydrocarbon ‘tails’.

BA C

phospholipid

(i) State in which area of the liposome, A, B or C, each of the following types of drug would be carried.

a hydrophilic drug .........................

a hydrophobic drug .......................

(ii) For the remaining position, A, B or C, explain why this would not be a suitable area for carrying a drug.

..................................................................................................................................

..................................................................................................................................[3]

(d) One way of carrying drugs in the bloodstream is to attach them by a chemical bond to a polymer. One such polymer is polyethylene glycol or PEG.

HO – (CH2 – CH2 – O)n – H

(i) Where would a drug be attached to a molecule of PEG?

..................................................................................................................................

(ii) Suggest why a liposome can carry more drug molecules than a molecule of PEG.

..................................................................................................................................

..................................................................................................................................[2]

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(e) Better-targeted delivery of drugs allows smaller amounts to be used, which brings significant advantages.

Suggest two advantages of using smaller drug doses.

..........................................................................................................................................

..........................................................................................................................................

..........................................................................................................................................

...................................................................................................................................... [2]

[Total: 10]



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DC (SM/CGW) 22690/3© UCLES 2010 [Turn over








*4308885825*

CHEMISTRY 9701/42


1 hour 45 minutes




1

2

3

4

5

6

7

8

Total

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© UCLES 2010 9701/42/M/J/10

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Use

Section A


1 Phenacyl chloride has been used as a component of some tear gases. Its lachrymatory and irritant properties are due to it reacting with water inside body tissues to produce hydrochloric acid.

It undergoes a nucleophilic substitution reaction with NaOH(aq).

O

+ OH–

phenacyl chloride

+

Cl

(a) Write the formulae of the products of this reaction in the two boxes above. [2]

When the rate of this reaction was measured at various concentrations of the two reagents, the following results were obtained.

experiment number [phenacyl chloride] [NaOH] relative rate

1 0.020 0.10 1.0

2 0.030 0.10 1.5

3 0.025 0.20 2.5

(b) (i) What is meant by the term order of reaction?

..................................................................................................................................

(ii) Use the above data to deduce the order with respect to each reactant. Explain your reasoning.

..................................................................................................................................

..................................................................................................................................

..................................................................................................................................

..................................................................................................................................

..................................................................................................................................

(iii) Write the overall rate equation for the reaction.

..................................................................................................................................

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© UCLES 2010 [Turn over9701/42/M/J/10

ForExaminer’s

Use

(iv) Describe the mechanism for this reaction that is consistent with your overall rate equation.

You should show all intermediates and/or transition states and partial charges, and you should represent the movements of electron pairs by curly arrows.

[7]

(c) (i) Describe an experiment that would show that CH3COCl reacts with water at a much faster rate than phenacyl chloride. Include the reagents you would use, and the observations you would make with each chloride.

..................................................................................................................................

..................................................................................................................................

..................................................................................................................................

..................................................................................................................................

..................................................................................................................................

..................................................................................................................................

..................................................................................................................................

(ii) Suggest an explanation for this difference in reactivity.

..................................................................................................................................

..................................................................................................................................[4]

[Total: 13]

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© UCLES 2010 9701/42/M/J/10

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Use

2 (a) Describe and explain how the solubilities of the sulfates of the Group II elements vary down the group.

..........................................................................................................................................

..........................................................................................................................................

..........................................................................................................................................

..........................................................................................................................................

..........................................................................................................................................

...................................................................................................................................... [3]

(b) The following table lists some enthalpy changes for magnesium and strontium compounds.

enthalpy change value for magnesium/ kJ mol–1

value for strontium/ kJ mol–1

lattice enthalpy of M (OH)2 –2993 –2467

enthalpy change of hydration of M 2+(g) –1890 –1414

enthalpy change of hydration of OH–(g) –550 –550

(i) Use the above data to calculate values of ΔH osolution for Mg(OH)2 and for Sr(OH)2.

Mg(OH)2 ...................................................................................................................

..................................................................................................................................

ΔH osolution = ..................................... kJ mol–1

Sr(OH)2 ....................................................................................................................

..................................................................................................................................


(ii) Use your results in (i) to suggest whether Sr(OH)2 is more or less soluble in water than is Mg(OH)2. State any assumptions you make.

..................................................................................................................................

..................................................................................................................................

(iii) Suggest whether Sr(OH)2 would be more or less soluble in hot water than in cold. Explain your reasoning.

..................................................................................................................................

..................................................................................................................................[5]

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(c) Calcium hydroxide, Ca(OH)2, is slightly soluble in water.

(i) Write an expression for Ksp for calcium hydroxide, and state its units.

Ksp = units ............................................

(ii) 25.0 cm3 of a saturated solution of Ca(OH)2 required 21.0 cm3 of 0.0500 mol dm–3 HCl for complete neutralisation.

Calculate the [OH–(aq)] and the [Ca2+(aq)] in the saturated solution, and hence calculate a value for Ksp.

[OH–(aq)] = .................................

[Ca2+(aq)] = ................................

Ksp = .........................................................................................

(iii) How would the solubility of Ca(OH)2 in 0.1 mol dm–3 NaOH compare with that in water?


..................................................................................................................................

..................................................................................................................................[6]

[Total: 14]

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© UCLES 2010 9701/42/M/J/10

ForExaminer’s

Use

3 (a) Fluorine is much more electronegative than both silicon and sulfur, but whereas the molecule of SF4 has an overall dipole, that of SiF4 has none.

Suggest a reason for this difference.

..........................................................................................................................................

...................................................................................................................................... [1]

(b) Predict whether or not the following molecules will have an overall dipole. Place a tick in the appropriate column.

compound molecule has anoverall dipole

molecule does not havean overall dipole

BCl 3

PCl 3

CCl 4

SF6

[2]

(c) Boron and silicon are two elements adjacent to carbon in the periodic table. CCl4 does not react with water, whereas BCl 3 and SiCl4 do react.

(i) Suggest a reason for this difference in reactivity.

..................................................................................................................................

..................................................................................................................................

(ii) Construct equations showing the reaction of these two chlorides with an excess of water.

BCl 3 .........................................................................................................................

SiCl4 .........................................................................................................................[3]

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(d) When reacted with a small quantity of water, SiCl 4 produces an oxychloride X, SixCl yOz. The mass spectrum of X shows peaks at mass numbers of 133, 149, 247, 263 and 396. (You should assume that the species responsible for all these peaks contain the 16O,

the 35Cl and the 28Si isotopes only.)

(i) Use these data to deduce the molecular formula of X.

molecular formula .........................................

(ii) Suggest the structures of the fragments responsible for the peaks at the following mass numbers.

mass number structure

133

247

263

(iii) Hence suggest the displayed formula of X.

[5]

[Total: 11]

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4 (a) Complete the electronic structures of the Cr3+ and Mn2+ ions.

Cr3+ 1s22s22p6 .............

Mn2+ 1s22s22p6 .............[2]

(b) (i) Describe what observations you would make when dilute KMnO4(aq) is added slowly and with shaking to an acidified solution of FeSO4(aq) until the KMnO4 is in a large excess.

..................................................................................................................................

..................................................................................................................................

..................................................................................................................................

..................................................................................................................................

..................................................................................................................................

..................................................................................................................................

(ii) Construct an ionic equation for the reaction that occurs.

..................................................................................................................................[4]

(c) By selecting relevant E o data from the Data Booklet explain why acidified solutions of Fe2+(aq) are relatively stable to oxidation by air, whereas a freshly prepared precipitate of Fe(OH)2 is readily oxidised to Fe(OH)3 under alkaline conditions.

relevant E o values and half equations

..........................................................................................................................................

..........................................................................................................................................

..........................................................................................................................................

..........................................................................................................................................

explanation

..........................................................................................................................................

..........................................................................................................................................[4]

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(d) Predict the organic products of the following reactions and draw their structures in the boxes below. You may use structural or skeletal formulae as you wish.

hot conc.MnO4

– + H+

hot conc.MnO4

– + H+

hotCr2O7

2– + H+

OH

OH

[4]

(e) KMnO4 and K2Cr2O7 are the reagents that can be used to carry out the following transformation.

E

I IICHO

OH

(i) Draw the structure of intermediate E in the box above.

(ii) Suggest reagents and conditions for the following.

reaction I ...................................................................................................................

reaction II ..................................................................................................................[3]

[Total: 17]

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5 (a) (i) Briefly explain why the benzene molecule is planar.

..................................................................................................................................

..................................................................................................................................

..................................................................................................................................

(ii) Briefly explain why all the carbon-carbon bonds in benzene are the same length.

..................................................................................................................................

..................................................................................................................................

..................................................................................................................................[2]

(b) Benzene can be nitrated by warming it with a mixture of concentrated sulfuric andnitric acids.

(i) By means of an equation, illustrate the initial role of the sulfuric acid in this reaction.

..................................................................................................................................

(ii) Name the type of reaction and describe the mechanism for the nitration reaction, including curly arrows showing the movement of electrons and all charges.

type of reaction .........................................................................................................

mechanism

[4]

(c) State the reagents and conditions needed to convert benzene into chlorobenzene.

...................................................................................................................................... [1]

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(d) Nitrobenzene undergoes further substitution considerably more slowly than chlorobenzene. In nitrobenzene the incoming group joins to the benzene ring in the 3-position, whereas

in chlorobenzene the incoming group joins to the benzene ring in the 4-position.

(i) Use these ideas to suggest the structures of the intermediate compounds Y and Z in the following synthesis of 4-chlorophenylamine.

I II

ZY

III

NH2

Cl

(ii) Suggest the reagents and conditions needed for reaction III in the above synthesis.

..................................................................................................................................

..................................................................................................................................

(iii) Suggest the structural formulae of the products A, B, C and D of the following reactions. If no reaction occurs write “no reaction” in the relevant box.

BA

DC

NH2

Br2(aq)

OH–(aq) NaNO2+ HCl

CH3COCl

Cl

[8]

[Total: 15]

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Section B


6 Human hair and silk both consist of proteins. Proteins are described as having three major levels of structure: primary, secondary and tertiary.

(a) Outline what is meant by the terms primary structure and tertiary structure of a protein.

primary structure ..............................................................................................................

..........................................................................................................................................

..........................................................................................................................................

tertiary structure ..............................................................................................................

..........................................................................................................................................

..........................................................................................................................................[2]

(b) In hair, the secondary structure consists of α-helices which are cross-linked bydisulfide bonds. The amino acid responsible for this cross-linking is cysteine, H2NCH(CH2SH)CO2H.

(i) Show by means of a diagram how the disulfide cross-links are formed.


..................................................................................................................................

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(iii) State three other interactions that stabilise the tertiary structure of proteins.

..................................................................................................................................

..................................................................................................................................

..................................................................................................................................[4]

(c) The β-pleated sheet is a different form of secondary structure found in proteins, such as those in silk.

(i) What type of bonding is responsible for stabilising the β-pleated sheet in silk?

..................................................................................................................................

(ii) On the diagram below, draw a second polypeptide strand and show how bonds would be formed that stabilise this β-pleated sheet.

N

H

CH CH

CHCH

R

O R H O R

C

N

H O R H O

C

N C

N C

[3]

(d) The cysteine-containing protein in hair is called α-keratin. A similar sequence of amino acids can produce β-keratin proteins found in the scales, claws and shells of reptiles such as tortoises. In β-keratin the secondary structure of the protein is in the form of a β-pleated sheet.

Suggest what makes the β-pleated sheet in β-keratin so much less flexible than the β-pleated sheet in silk.

..........................................................................................................................................

..........................................................................................................................................

...................................................................................................................................... [1]

[Total: 10]

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7 A mixture of amino acids may be separated using electrophoresis. A typical practical set-up is shown in the diagram.

d.c. power supply

+ –glass slides

filter paper soaked in buffer solutionamino acid mixture placed here

electrolyte

(a) When the power supply is switched on, some amino acids may not move, but remain stationary. Suggest an explanation for this observation.

..........................................................................................................................................

..........................................................................................................................................

...................................................................................................................................... [2]

(b) The amino acid glycine has the formula H2NCH2CO2H. Identify the species formed on the filter paper if glycine moves to the left (positive) end of the filter paper.

.................................................................. [1]

(c) The following result was obtained from another electrophoresis. What can be deduced about the relative sizes of, and charges on, the amino acid species A, B and C?

A

+ –

B

mixture placed here

C

amino acid relative size charge

A

B

C

[3]

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(d) The sequence of amino acids in a polypeptide may be determined by partial hydrolysis of the chain into smaller pieces, often tripeptides.

(i) Following such a partial hydrolysis, the following tripeptides were obtained from a given polypeptide.

ala-gly-asp gly-ala-gly lys-val-ser ser-ala-gly val-ser-ala

Given that the N-terminal amino acid is lysine (lys) suggest the amino acid sequence of the shortest polypeptide that would give the above tripeptides.

..................................................................................................................................

The structural formulae of the amino acids in the polypeptide are given below.

abbreviation amino acid structural formula

ala alanine H2NCH(CH3)CO2H

asp aspartic acid H2NCH(CH2CO2H)CO2H

gly glycine H2NCH2CO2H

lys lysine H2NCH(CH2CH2CH2CH2NH2)CO2H

ser serine H2NCH(CH2OH)CO2H

val valine H2NCH(CH(CH3)2)CO2H

(ii) Which of the tripeptides in (i) has the lowest Mr?

..........................................................................

(iii) Select one amino acid from those listed in the table which contains an ionicside-chain at pH 8.

..........................................................................

[4]

[Total: 10]

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8 The design and development of batteries has been a major research area in recent years.

(a) Lead-acid batteries, used in cars, are made up of a number of rechargeable cells in series, and were first developed in 1860. They have the disadvantage of a relatively high mass compared to the energy stored. During discharge, the electrode reactions in the cells of these batteries are as follows.

I Pb + SO42– PbSO4 + 2e–

II PbO2 + 4H+ + SO42– + 2e– PbSO4 + 2H2O

State which of these reactions occurs at the positive electrode in a lead-acid cell during discharge, explaining your answer.

..........................................................................................................................................

...................................................................................................................................... [1]

(b) Use the Data Booklet and the equations I and II above to calculate the voltage produced by a lead-acid cell under standard conditions.

[2]

(c) Nickel-metal hydride batteries were developed in the 1980s and have become increasingly common particularly for small devices such as mobile phones and digital cameras that need near-constant sources of electrical energy. These cells use nickel oxohydroxide (NiO(OH)) as one electrode and a hydrogen-absorbing alloy such as LiNi5 as the other electrode.

One reaction that takes place in these batteries is

NiO(OH) + H2O + e– Ni(OH)2 + OH–

(i) State the oxidation state of nickel in NiO(OH). .....................

(ii) Suggest a likely advantage of these batteries compared with lead-acid batteries.

..................................................................................................................................

..................................................................................................................................[2]

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(d) Hydrogen fuel cells have been suggested as the next major advance in electrically powered vehicles. In these fuel cells hydrogen is oxidized to produce water, using a catalyst and inert electrodes.

(i) Suggest a material for the electrodes.

..........................................................................

(ii) Use your knowledge of hydrogen to suggest a disadvantage of these fuel cells in powering vehicles.

..................................................................................................................................

..................................................................................................................................[2]

(e) Many of the world’s countries are developing ways of recycling materials which are valuable or which require large amounts of energy to produce.

For each of the following recyclable materials, state whether recycling of this material is important in saving energy or in saving resources. Use your knowledge of chemistry to explain each choice.

glass ................................................................................................................................

..........................................................................................................................................

..........................................................................................................................................

steel .................................................................................................................................

..........................................................................................................................................

..........................................................................................................................................

plastics .............................................................................................................................

..........................................................................................................................................

..........................................................................................................................................[3]

[Total: 10]

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DC (SM/CGW) 27852© UCLES 2010 [Turn over








*9125855431*

CHEMISTRY 9701/43


1 hour 45 minutes




1

2

3

4

5

6

7

8

Total

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© UCLES 2010 9701/43/M/J/10

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Section A


1 Phenacyl chloride has been used as a component of some tear gases. Its lachrymatory and irritant properties are due to it reacting with water inside body tissues to produce hydrochloric acid.

It undergoes a nucleophilic substitution reaction with NaOH(aq).

O

+ OH–

phenacyl chloride

+

Cl

(a) Write the formulae of the products of this reaction in the two boxes above. [2]

When the rate of this reaction was measured at various concentrations of the two reagents, the following results were obtained.

experiment number [phenacyl chloride] [NaOH] relative rate

1 0.020 0.10 1.0

2 0.030 0.10 1.5

3 0.025 0.20 2.5

(b) (i) What is meant by the term order of reaction?

..................................................................................................................................

(ii) Use the above data to deduce the order with respect to each reactant. Explain your reasoning.

..................................................................................................................................

..................................................................................................................................

..................................................................................................................................

..................................................................................................................................

..................................................................................................................................

(iii) Write the overall rate equation for the reaction.

..................................................................................................................................

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(iv) Describe the mechanism for this reaction that is consistent with your overall rate equation.

You should show all intermediates and/or transition states and partial charges, and you should represent the movements of electron pairs by curly arrows.

[7]

(c) (i) Describe an experiment that would show that CH3COCl reacts with water at a much faster rate than phenacyl chloride. Include the reagents you would use, and the observations you would make with each chloride.

..................................................................................................................................

..................................................................................................................................

..................................................................................................................................

..................................................................................................................................

..................................................................................................................................

..................................................................................................................................

..................................................................................................................................

(ii) Suggest an explanation for this difference in reactivity.

..................................................................................................................................

..................................................................................................................................[4]

[Total: 13]

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2 (a) Describe and explain how the solubilities of the sulfates of the Group II elements vary down the group.

..........................................................................................................................................

..........................................................................................................................................

..........................................................................................................................................

..........................................................................................................................................

..........................................................................................................................................

...................................................................................................................................... [3]

(b) The following table lists some enthalpy changes for magnesium and strontium compounds.

enthalpy change value for magnesium/ kJ mol–1

value for strontium/ kJ mol–1

lattice enthalpy of M (OH)2 –2993 –2467

enthalpy change of hydration of M 2+(g) –1890 –1414

enthalpy change of hydration of OH–(g) –550 –550

(i) Use the above data to calculate values of ΔH osolution for Mg(OH)2 and for Sr(OH)2.

Mg(OH)2 ...................................................................................................................

..................................................................................................................................


Sr(OH)2 ....................................................................................................................

..................................................................................................................................


(ii) Use your results in (i) to suggest whether Sr(OH)2 is more or less soluble in water than is Mg(OH)2. State any assumptions you make.

..................................................................................................................................

..................................................................................................................................

(iii) Suggest whether Sr(OH)2 would be more or less soluble in hot water than in cold. Explain your reasoning.

..................................................................................................................................

..................................................................................................................................[5]

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(c) Calcium hydroxide, Ca(OH)2, is slightly soluble in water.

(i) Write an expression for Ksp for calcium hydroxide, and state its units.

Ksp = units ............................................

(ii) 25.0 cm3 of a saturated solution of Ca(OH)2 required 21.0 cm3 of 0.0500 mol dm–3 HCl for complete neutralisation.

Calculate the [OH–(aq)] and the [Ca2+(aq)] in the saturated solution, and hence calculate a value for Ksp.

[OH–(aq)] = .................................

[Ca2+(aq)] = ................................

Ksp = .........................................................................................

(iii) How would the solubility of Ca(OH)2 in 0.1 mol dm–3 NaOH compare with that in water?


..................................................................................................................................

..................................................................................................................................[6]

[Total: 14]

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3 (a) Fluorine is much more electronegative than both silicon and sulfur, but whereas the molecule of SF4 has an overall dipole, that of SiF4 has none.

Suggest a reason for this difference.

..........................................................................................................................................

...................................................................................................................................... [1]

(b) Predict whether or not the following molecules will have an overall dipole. Place a tick in the appropriate column.

compound molecule has anoverall dipole

molecule does not havean overall dipole

BCl 3

PCl 3

CCl 4

SF6

[2]

(c) Boron and silicon are two elements adjacent to carbon in the periodic table. CCl4 does not react with water, whereas BCl 3 and SiCl4 do react.

(i) Suggest a reason for this difference in reactivity.

..................................................................................................................................

..................................................................................................................................

(ii) Construct equations showing the reaction of these two chlorides with an excess of water.

BCl 3 .........................................................................................................................

SiCl4 .........................................................................................................................[3]

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(d) When reacted with a small quantity of water, SiCl 4 produces an oxychloride X, SixCl yOz. The mass spectrum of X shows peaks at mass numbers of 133, 149, 247, 263 and 396. (You should assume that the species responsible for all these peaks contain the 16O,

the 35Cl and the 28Si isotopes only.)

(i) Use these data to deduce the molecular formula of X.

molecular formula .........................................

(ii) Suggest the structures of the fragments responsible for the peaks at the following mass numbers.

mass number structure

133

247

263

(iii) Hence suggest the displayed formula of X.

[5]

[Total: 11]

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4 (a) Complete the electronic structures of the Cr3+ and Mn2+ ions.

Cr3+ 1s22s22p6 .............

Mn2+ 1s22s22p6 .............[2]

(b) (i) Describe what observations you would make when dilute KMnO4(aq) is added slowly and with shaking to an acidified solution of FeSO4(aq) until the KMnO4 is in a large excess.

..................................................................................................................................

..................................................................................................................................

..................................................................................................................................

..................................................................................................................................

..................................................................................................................................

..................................................................................................................................

(ii) Construct an ionic equation for the reaction that occurs.

..................................................................................................................................[4]

(c) By selecting relevant E o data from the Data Booklet explain why acidified solutions of Fe2+(aq) are relatively stable to oxidation by air, whereas a freshly prepared precipitate of Fe(OH)2 is readily oxidised to Fe(OH)3 under alkaline conditions.

relevant E o values and half equations

..........................................................................................................................................

..........................................................................................................................................

..........................................................................................................................................

..........................................................................................................................................

explanation

..........................................................................................................................................

..........................................................................................................................................[4]

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(d) Predict the organic products of the following reactions and draw their structures in the boxes below. You may use structural or skeletal formulae as you wish.

hot conc.MnO4

– + H+

hot conc.MnO4

– + H+

hotCr2O7

2– + H+

OH

OH

[4]

(e) KMnO4 and K2Cr2O7 are the reagents that can be used to carry out the following transformation.

E

I IICHO

OH

(i) Draw the structure of intermediate E in the box above.

(ii) Suggest reagents and conditions for the following.

reaction I ...................................................................................................................

reaction II ..................................................................................................................[3]

[Total: 17]

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5 (a) (i) Briefly explain why the benzene molecule is planar.

..................................................................................................................................

..................................................................................................................................

..................................................................................................................................

(ii) Briefly explain why all the carbon-carbon bonds in benzene are the same length.

..................................................................................................................................

..................................................................................................................................

..................................................................................................................................[2]

(b) Benzene can be nitrated by warming it with a mixture of concentrated sulfuric andnitric acids.

(i) By means of an equation, illustrate the initial role of the sulfuric acid in this reaction.

..................................................................................................................................

(ii) Name the type of reaction and describe the mechanism for the nitration reaction, including curly arrows showing the movement of electrons and all charges.

type of reaction .........................................................................................................

mechanism

[4]

(c) State the reagents and conditions needed to convert benzene into chlorobenzene.

...................................................................................................................................... [1]

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(d) Nitrobenzene undergoes further substitution considerably more slowly than chlorobenzene. In nitrobenzene the incoming group joins to the benzene ring in the 3-position, whereas

in chlorobenzene the incoming group joins to the benzene ring in the 4-position.

(i) Use these ideas to suggest the structures of the intermediate compounds Y and Z in the following synthesis of 4-chlorophenylamine.

I II

ZY

III

NH2

Cl

(ii) Suggest the reagents and conditions needed for reaction III in the above synthesis.

..................................................................................................................................

..................................................................................................................................

(iii) Suggest the structural formulae of the products A, B, C and D of the following reactions. If no reaction occurs write “no reaction” in the relevant box.

BA

DC

NH2

Br2(aq)

OH–(aq) NaNO2+ HCl

CH3COCl

Cl

[8]

[Total: 15]

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Use

Section B


6 Human hair and silk both consist of proteins. Proteins are described as having three major levels of structure: primary, secondary and tertiary.

(a) Outline what is meant by the terms primary structure and tertiary structure of a protein.

primary structure ..............................................................................................................

..........................................................................................................................................

..........................................................................................................................................

tertiary structure ..............................................................................................................

..........................................................................................................................................

..........................................................................................................................................[2]

(b) In hair, the secondary structure consists of α-helices which are cross-linked bydisulfide bonds. The amino acid responsible for this cross-linking is cysteine, H2NCH(CH2SH)CO2H.

(i) Show by means of a diagram how the disulfide cross-links are formed.


..................................................................................................................................

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(iii) State three other interactions that stabilise the tertiary structure of proteins.

..................................................................................................................................

..................................................................................................................................

..................................................................................................................................[4]

(c) The β-pleated sheet is a different form of secondary structure found in proteins, such as those in silk.

(i) What type of bonding is responsible for stabilising the β-pleated sheet in silk?

..................................................................................................................................

(ii) On the diagram below, draw a second polypeptide strand and show how bonds would be formed that stabilise this β-pleated sheet.

N

H

CH CH

CHCH

R

O R H O R

C

N

H O R H O

C

N C

N C

[3]

(d) The cysteine-containing protein in hair is called α-keratin. A similar sequence of amino acids can produce β-keratin proteins found in the scales, claws and shells of reptiles such as tortoises. In β-keratin the secondary structure of the protein is in the form of a β-pleated sheet.

Suggest what makes the β-pleated sheet in β-keratin so much less flexible than the β-pleated sheet in silk.

..........................................................................................................................................

..........................................................................................................................................

...................................................................................................................................... [1]

[Total: 10]

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7 A mixture of amino acids may be separated using electrophoresis. A typical practical set-up is shown in the diagram.

d.c. power supply

+ –glass slides

filter paper soaked in buffer solutionamino acid mixture placed here

electrolyte

(a) When the power supply is switched on, some amino acids may not move, but remain stationary. Suggest an explanation for this observation.

..........................................................................................................................................

..........................................................................................................................................

...................................................................................................................................... [2]

(b) The amino acid glycine has the formula H2NCH2CO2H. Identify the species formed on the filter paper if glycine moves to the left (positive) end of the filter paper.

.................................................................. [1]

(c) The following result was obtained from another electrophoresis. What can be deduced about the relative sizes of, and charges on, the amino acid species A, B and C?

A

+ –

B

mixture placed here

C

amino acid relative size charge

A

B

C

[3]

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(d) The sequence of amino acids in a polypeptide may be determined by partial hydrolysis of the chain into smaller pieces, often tripeptides.

(i) Following such a partial hydrolysis, the following tripeptides were obtained from a given polypeptide.

ala-gly-asp gly-ala-gly lys-val-ser ser-ala-gly val-ser-ala

Given that the N-terminal amino acid is lysine (lys) suggest the amino acid sequence of the shortest polypeptide that would give the above tripeptides.

..................................................................................................................................

The structural formulae of the amino acids in the polypeptide are given below.

abbreviation amino acid structural formula

ala alanine H2NCH(CH3)CO2H

asp aspartic acid H2NCH(CH2CO2H)CO2H

gly glycine H2NCH2CO2H

lys lysine H2NCH(CH2CH2CH2CH2NH2)CO2H

ser serine H2NCH(CH2OH)CO2H

val valine H2NCH(CH(CH3)2)CO2H

(ii) Which of the tripeptides in (i) has the lowest Mr?

..........................................................................

(iii) Select one amino acid from those listed in the table which contains an ionicside-chain at pH 8.

..........................................................................

[4]

[Total: 10]

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8 The design and development of batteries has been a major research area in recent years.

(a) Lead-acid batteries, used in cars, are made up of a number of rechargeable cells in series, and were first developed in 1860. They have the disadvantage of a relatively high mass compared to the energy stored. During discharge, the electrode reactions in the cells of these batteries are as follows.

I Pb + SO42– PbSO4 + 2e–

II PbO2 + 4H+ + SO42– + 2e– PbSO4 + 2H2O

State which of these reactions occurs at the positive electrode in a lead-acid cell during discharge, explaining your answer.

..........................................................................................................................................

...................................................................................................................................... [1]

(b) Use the Data Booklet and the equations I and II above to calculate the voltage produced by a lead-acid cell under standard conditions.

[2]

(c) Nickel-metal hydride batteries were developed in the 1980s and have become increasingly common particularly for small devices such as mobile phones and digital cameras that need near-constant sources of electrical energy. These cells use nickel oxohydroxide (NiO(OH)) as one electrode and a hydrogen-absorbing alloy such as LiNi5 as the other electrode.

One reaction that takes place in these batteries is

NiO(OH) + H2O + e– Ni(OH)2 + OH–

(i) State the oxidation state of nickel in NiO(OH). .....................

(ii) Suggest a likely advantage of these batteries compared with lead-acid batteries.

..................................................................................................................................

..................................................................................................................................[2]

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(d) Hydrogen fuel cells have been suggested as the next major advance in electrically powered vehicles. In these fuel cells hydrogen is oxidized to produce water, using a catalyst and inert electrodes.

(i) Suggest a material for the electrodes.

..........................................................................

(ii) Use your knowledge of hydrogen to suggest a disadvantage of these fuel cells in powering vehicles.

..................................................................................................................................

..................................................................................................................................[2]

(e) Many of the world’s countries are developing ways of recycling materials which are valuable or which require large amounts of energy to produce.

For each of the following recyclable materials, state whether recycling of this material is important in saving energy or in saving resources. Use your knowledge of chemistry to explain each choice.

glass ................................................................................................................................

..........................................................................................................................................

..........................................................................................................................................

steel .................................................................................................................................

..........................................................................................................................................

..........................................................................................................................................

plastics .............................................................................................................................

..........................................................................................................................................

..........................................................................................................................................[3]

[Total: 10]

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DC (AT/KN) 11584/3© UCLES 2010 [Turn over



Write your Centre number, candidate number and name on all the work you hand in.Write in dark blue or black pen.You may use a soft pencil for any diagrams, graphs or rough working.Do not use staples, paper clips, highlighters, glue or correction fluid.DO NOT WRITE IN ANY BARCODES.



*8689143754*

CHEMISTRY 9701/51

Paper 5 Planning, Analysis and Evaluation May/June 2010

1 hour 15 minutes


No Additional Materials are required.


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1 The neutralisation of an acid by a base is exothermic.

In this experiment the following solutions are available.

2 mol dm–3 sulfuric acid, H2SO4 3 mol dm–3 sodium hydroxide, NaOH

The equation for the reaction is:

2NaOH(aq) + H2SO4(aq) Na2SO4(aq) + 2H2O(l)

(a) 2 mol dm–3 H2SO4 is gradually added to a fixed volume of 3 mol dm–3 NaOH in a 150 cm3 plastic cup, while stirring continuously. The temperature of the solution, measured with a thermometer, increases until the alkali is just neutralised. On further addition of the cold acid the temperature of the solution slowly falls.

Select an appropriate volume, x cm3, of 3 mol dm–3 NaOH to use in the experiment.

..................................... cm3

Calculate the volume of 2 mol dm–3 H2SO4 that will just neutralise x cm3 of 3 mol dm–3 NaOH.

Sketch the graph you would expect to obtain as the acid is added. Label the neutralisation point.

volume of acid added / cm30

temperatureof thesolution / °C

[3]

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(b) This experiment can be used to determine the enthalpy change of neutralisation for the reaction. To ensure reliable results the experiment should be repeated a number of times.

When sulfuric acid is added to the fixed volume of aqueous sodium hydroxide in this experiment

(i) the independent variable is ..................................................................................... ,

(ii) the dependent variable is ........................................................................................ ,

(iii) the other variables that need to be controlled are .....................................................

................................................................................................................................ . [3]

(c) In carrying out the experiment, what apparatus would you use to accurately measure the independent variable?

......................................................................................................................................[1]

(d) Explain how you would use this apparatus to control the independent variable.

..........................................................................................................................................

......................................................................................................................................[1]

(e) Identify and assess

(i) a risk associated with the plastic cup used in this experiment,

..................................................................................................................................

..................................................................................................................................

(ii) a risk associated with the 3 mol dm–3 NaOH.

..................................................................................................................................

.................................................................................................................................. [1]

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(f) Describe how the risks in (e) can be kept to a minimum for

(i) the plastic cup,

..................................................................................................................................

..................................................................................................................................

(ii) the 3 mol dm–3 NaOH.

..................................................................................................................................

.................................................................................................................................. [1]

(g) In the space below draw a table to show column headings for all of the measurements you would make during the experiment.

Include in the table one or more columns for any calculated values needed to determine the enthalpy change of neutralisation.

[2]

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(h) Show how you would calculate the total heat energy produced in the plastic cup up to the point when the sulfuric acid has just neutralised the sodium hydroxide.

You may use ΔT to represent the temperature change.

[4.3 J of heat energy raise the temperature of 1 cm3 of any solution by 1 °C.]

[1]

(i) The enthalpy change of neutralisation is the energy change associated with the reaction shown by the following equation.

NaOH(aq) + 12 H2SO4(aq) 1

2 Na2SO4(aq) + H2O(l)

Show how you would convert the energy change expressed in (h) into a value, in kJ mol–1, for the enthalpy change of neutralisation, ΔHneutralisation.

Show clearly the sign and the expression for the enthalpy change.

ΔHneutralisation = .......... ..................................... kJ mol–1 [2]sign expression

[Total: 15]

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2 A student reads in a text-book about ideal and non-ideal mixtures of liquids.

When two different liquids are mixed, bonds between molecules in each of the different liquids are broken and new bonds are formed between the different molecules in the mixture.

In an ideal mixture the energy used to break bonds between molecules in the different liquids is approximately the same as the energy released when new bonds are formed between molecules in the mixture.

In a non-ideal mixture the energy used to break bonds in the different liquids is not the same as that released in bond formation.

The breaking of bonds is an endothermic process.The formation of bonds is an exothermic process.

In order to test this information, the student investigates a number of mixtures of

(i) propan-1-ol, CH3CH2CH2OH, and propan-2-ol, CH3CHOHCH3, (ii) ethanol, CH3CH2OH, and cyclohexane, C6H12.

The boiling point of each pure liquid and each mixture is measured. The thermometer used has graduations at 0.2 °C.

The results for the experiment with propan-1-ol and propan-2-ol, which was carried out four times, are shown on the next page.

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/ °C%

(by volume) of propan-1-ol in

mixture

mean boiling temperature

/ °Cpropan-1-ol propan-2-ol 1 2 3 4

0 20.00 82.1 82.6 82.7 82.2

4.00 16.00 85.3 85.4 85.5 85.4

8.00 12.00 88.5 88.4 88.1 88.2

12.00 8.00 91.3 90.6 91.2 91.4

16.00 4.00 94.2 94.0 94.3 94.3

20.00 0 97.1 97.3 97.2 97.8

(a) Indicate below any results that you consider to be anomalies and that should not be included when calculating the mean boiling temperature.

..........................................................................................................................................

.......................................................................................................................................... [1]

(b) Complete the table above to show the following.

(i) the percentage (%) by volume of propan-1-ol in each of the liquids / mixtures

(ii) the mean boiling temperature for each of the liquids/mixtures [2]

The experiment is repeated using mixtures of ethanol and cyclohexane. The results of these experiments are given in the table below.

volume / cm3 %(by volume) of

ethanol in mixture

mean boiling temperature

/ °Cethanol cyclohexane

0 20.00 0 81.4

2.00 18.00 10.0 66.5

6.00 14.00 30.0 65.0

10.00 10.00 50.0 65.3

14.00 6.00 70.0 65.5

18.00 2.00 90.0 68.0

20.00 0 100.0 78.5

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(c) For both graphs below, use as much of the y-axis as possible for experimental data.Do not start your temperature scales at 0 °C.

Draw a graph of mean boiling temperature ( y-axis) against the % of propan-1-ol (x-axis) in the mixture of propan-1-ol and propan-2-ol.

Draw a graph of mean boiling temperature ( y-axis) against the % of ethanol (x-axis) in the mixture of ethanol and cyclohexane.

[3]

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(d) The graph you have drawn for propan-1-ol and propan-2-ol is typical of ideal mixtures of liquids.

The graph you have drawn for ethanol and cyclohexane is typical of some non-ideal mixtures of liquids.

From the shape of your graph explain whether the mixing of ethanol and cyclohexane is overall an endothermic or an exothermic process.

The mixing of ethanol and cyclohexane is ..................................................................... ,

because ...........................................................................................................................

..........................................................................................................................................

..........................................................................................................................................

What type of intermolecular forces exist between the molecules of

(i) pure ethanol, ............................................................................................................

..................................................................................................................................

(ii) pure cyclohexane, ....................................................................................................

..................................................................................................................................

(iii) ethanol and cyclohexane in the mixture?

.................................................................................................................................. [3]

[Total: 9]

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3 A group of students perform an experiment to confirm that the formula of magnesium oxide is MgO. Each student is provided with a different length of magnesium ribbon which is coiled and heated in a crucible fitted with a lid. The magnesium reacts with oxygen to form magnesium oxide.

The instructions for the experiment are as follows.

• Weigh the empty crucible and lid. • Coil the length of magnesium ribbon and place it in the bottom of the crucible. • Reweigh the crucible and lid with the magnesium. • Heat the crucible with a Bunsen burner. • Periodically lift the crucible lid for a very short period of time. This allows air to enter

the crucible. • Each time the lid is lifted, take care to minimise the loss of any white smoke which

is some of the powder formed. • When the reaction appears to have stopped, remove the crucible lid and heat the

crucible and its contents strongly for 2 minutes. • Cool and reweigh the crucible, lid and the contents.

The results of the experiment are given below.

studentmass of

crucible and lid

mass of crucible and lid + magnesium

mass of crucible and lid + magnesium

oxide

mass of magnesium

mass of magnesium

oxide

/ g / g / g / g / g

1 25.37 26.62 27.50

2 25.18 27.01 28.19 1.83 3.01

3 25.44 27.73 29.19 2.29 3.75

4 25.26 27.71 24.96 2.45

5 25.39 28.11 29.84 2.72 4.45

6 25.04 27.89 28.54 2.85 3.50

7 25.13 28.08 29.93

(a) Complete the table above for student 1, student 4 and student 7.

Plot the data for student 1 and for student 7 on the graph on the next page.[1]

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(b) If the formula of magnesium oxide is MgO, the straight line indicates the mass of magnesium oxide formed from a given mass of magnesium.

0.000.00

1.00

2.00

3.00

4.00

5.00

1.00 2.00 3.00

mass ofmagnesium

oxide / g

mass of magnesium / g

×

×

×

×

Choose a mass of Mg and use the straight line to determine the corresponding mass of MgO formed.

.............................. g of magnesium form .............................. g of magnesium oxide. [1]

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© UCLES 2010 9701/51/M/J/10

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(c) Show by calculation that the masses of magnesium and magnesium oxide selected in (b) correspond to a formula of MgO.

[Ar: O,16.0; Mg, 24.3]

[1]

(d) The point plotted for student 6 shows a large deviation from the straight line. Refer to the instructions for the experiment and suggest a possible explanation for this

anomalous result.

..........................................................................................................................................

..........................................................................................................................................

......................................................................................................................................[1]

(e) The result for student 4 could not be plotted on the graph. Suggest an error in carrying out the experiment that could have led to this result.

..........................................................................................................................................

..........................................................................................................................................

......................................................................................................................................[1]

(f) Student 1 added a few drops of water to the cooled residue in the crucible. The residue and water reacted to produce ammonia gas, NH3. Explain why this observation reduces confidence in this experiment as a method for

determining the formula of magnesium oxide.

..........................................................................................................................................

..........................................................................................................................................

......................................................................................................................................[1]

[Total: 6]

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DC (SM/SW) 23107/2© UCLES 2010 [Turn over






*6089013879*

CHEMISTRY 9701/52


1 hour 15 minutes




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ForExaminer’s

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1 At any temperature, equilibrium can be established between a liquid X and the vapour given off by that liquid.

X (l) X (g)

As the temperature of the system is raised, so the pressure exerted by the vapour increases. When the vapour pressure becomes equal to the surrounding (ambient) air pressure, the liquid boils.

When the liquid contains a dissolved solid (solute), the vapour pressure above the liquid is reduced.

You are to plan an experiment to investigate how the boiling point of an aqueous solution of potassium chloride depends on the concentration of the solution.

(a) (i) By considering how the vapour pressure changes as the concentration of the aqueous potassium chloride increases, predict and explain how the boiling point of the solution will be affected by the concentration of the solution.

Predict how the boiling point will change ..................................................................

..................................................................................................................................

..................................................................................................................................

Explanation ..............................................................................................................

..................................................................................................................................

..................................................................................................................................

(ii) Display your prediction in the form of a sketch graph, labelling clearly the point representing the boiling point of pure water and its value.

concentration of the potassium chloride

boiling point

0

[3]

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(b) In the experiment you are about to plan, identify the following.

(i) the independent variable ..........................................................................................

(ii) the dependent variable .............................................................................................[2]

(c) Draw a diagram of the apparatus you would use in the experiment. Your apparatus should use only standard items found in a school or college laboratory and should show clearly

(i) how the solution will be heated and over-heating of the solution prevented,

(ii) how the thermometer will be positioned. Remember you are investigating an equilibrium.

Label each piece of apparatus used, indicating its size or capacity and the temperature range that the thermometer should cover.

[3]

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(d) When investigating how the boiling point of a solution changes with concentration, it is convenient to represent the concentrations of the solute as a molality.

The molality of a solution is defined as the number of moles of a solute dissolved in one kilogram of water e.g. a one molal solution has one mole of solute dissolved in one kilogram of water.

In addition to the standard apparatus present in a laboratory you are provided with the following materials.

100 g of distilled/deionised water (you should take particular note of this limited supply of water)

solid potassium chloride, KCl

Give a step-by-step description of how you would

(i) prepare a series of solutions of potassium chloride that can be used in the apparatus you have shown in (c) to give sufficient data to plot a graph as in (a)(ii),

(ii) show how you would calculate the molality of one of these solutions. [Ar: K, 39.1; Cl, 35.5]

..................................................................................................................................

..................................................................................................................................

..................................................................................................................................

..................................................................................................................................

..................................................................................................................................

..................................................................................................................................

..................................................................................................................................

..................................................................................................................................

..................................................................................................................................

..................................................................................................................................

..................................................................................................................................

..................................................................................................................................

..................................................................................................................................

..................................................................................................................................

..............................................................................................................................[3]

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(e) State a hazard that must be considered when planning the experiment.

..........................................................................................................................................

......................................................................................................................................[1]

(f) State a limiting factor that must be taken into account when increasing the concentration of the aqueous potassium chloride.

..........................................................................................................................................

..........................................................................................................................................

......................................................................................................................................[1]

(g) Draw up a table with appropriate headings to show the data you would record when carrying out your experiments and the values you would calculate in order to construct a graph to support or reject your prediction in (a). The headings should include the appropriate units.

[2]

[Total: 15]

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6

2 When aqueous sodium hydroxide, NaOH, is added to aqueous copper(II) sulfate, CuSO4,a precipitate of copper(II) hydroxide, Cu(OH)2, is produced.

The stoichiometric equation for this reaction is

CuSO4 (aq) + 2NaOH (aq) Cu(OH)2 (s) + Na2SO4 (aq)

An experiment was carried out to investigate this stoichiometry. • A weighed sample of copper(II) sulfate-5-water, CuSO4.5H2O, was completely dissolved

in distilled water. • An excess of aqueous sodium hydroxide was added. • The resultant precipitate was filtered off. • The precipitate was washed thoroughly and completely dried. • The mass of the precipitate was recorded.

(a) Calculate the relative formular mass, Mr, of each of the following. [Ar: Cu, 63.5; S, 32.1; O, 16.0; H, 1.0]

CuSO4.5H2O Cu(OH)2

Mr Mr

[1]

(b) The results of the experiment are recorded below.

A B C D Emass of

CuSO4.5H2O/ g

mass ofCu(OH)2

/ g

2.50 0.78

6.24 1.95

9.99 3.12

14.98 4.20

19.97 6.24

24.96 7.80

29.95 9.36

34.94 11.81

42.43 13.26

Process the results in the table to calculate the number of moles of CuSO4.5H2O used and the number of moles of Cu(OH)2 produced, to enable you to plot a graph to show the relative number of moles of the CuSO4.5H2O and Cu(OH)2.

Record these values to three decimal places in the additional columns of the table.You may use some or all of the columns.

Label the columns you use. For each column you use, include units where appropriate and an expression to show

how your values are calculated. You may use the column headings A to E in your expressions. [2]

(c) Why was it not necessary to know the concentration of the aqueous sodium hydroxide?

..........................................................................................................................................

......................................................................................................................................[1]

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(d) Present the data calculated in (b) in graphical form. Draw the line of best fit.

[3]

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(e) Circle on the graph any point(s) you consider to be anomalous. For any point circled on the graph suggest an error in the conduct of the experiment that

might have led to an anomalous result.

..........................................................................................................................................

..........................................................................................................................................

..........................................................................................................................................

..........................................................................................................................................

..........................................................................................................................................

..........................................................................................................................................

..........................................................................................................................................

......................................................................................................................................[3]

(f) Determine the slope of the graph. Mark clearly on the graph any construction lines and show clearly in your calculation how the intercepts were used in the calculation of the slope.

[3]

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(g) State whether the result in (f) confirms or not the stoichiometry of the equation for the reaction between aqueous copper(II) sulfate and aqueous sodium hydroxide.

..........................................................................................................................................

..........................................................................................................................................

..........................................................................................................................................

..........................................................................................................................................

Comment on your conclusion.

..........................................................................................................................................

..........................................................................................................................................

..........................................................................................................................................

..........................................................................................................................................

..........................................................................................................................................

..........................................................................................................................................[2]

[Total: 15]

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DC (SM/SW) 27888© UCLES 2010 [Turn over






*0281936391*

CHEMISTRY 9701/53


1 hour 15 minutes




1

2

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9701/53/M/J/10© UCLES 2010

ForExaminer’s

Use

1 At any temperature, equilibrium can be established between a liquid X and the vapour given off by that liquid.

X (l) X (g)

As the temperature of the system is raised, so the pressure exerted by the vapour increases. When the vapour pressure becomes equal to the surrounding (ambient) air pressure, the liquid boils.

When the liquid contains a dissolved solid (solute), the vapour pressure above the liquid is reduced.

You are to plan an experiment to investigate how the boiling point of an aqueous solution of potassium chloride depends on the concentration of the solution.

(a) (i) By considering how the vapour pressure changes as the concentration of the aqueous potassium chloride increases, predict and explain how the boiling point of the solution will be affected by the concentration of the solution.

Predict how the boiling point will change ..................................................................

..................................................................................................................................

..................................................................................................................................

Explanation ..............................................................................................................

..................................................................................................................................

..................................................................................................................................

(ii) Display your prediction in the form of a sketch graph, labelling clearly the point representing the boiling point of pure water and its value.

concentration of the potassium chloride

boiling point

0

[3]

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ForExaminer’s

Use

(b) In the experiment you are about to plan, identify the following.

(i) the independent variable ..........................................................................................

(ii) the dependent variable .............................................................................................[2]

(c) Draw a diagram of the apparatus you would use in the experiment. Your apparatus should use only standard items found in a school or college laboratory and should show clearly

(i) how the solution will be heated and over-heating of the solution prevented,

(ii) how the thermometer will be positioned. Remember you are investigating an equilibrium.

Label each piece of apparatus used, indicating its size or capacity and the temperature range that the thermometer should cover.

[3]

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ForExaminer’s

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(d) When investigating how the boiling point of a solution changes with concentration, it is convenient to represent the concentrations of the solute as a molality.

The molality of a solution is defined as the number of moles of a solute dissolved in one kilogram of water e.g. a one molal solution has one mole of solute dissolved in one kilogram of water.

In addition to the standard apparatus present in a laboratory you are provided with the following materials.

100 g of distilled/deionised water (you should take particular note of this limited supply of water)

solid potassium chloride, KCl

Give a step-by-step description of how you would

(i) prepare a series of solutions of potassium chloride that can be used in the apparatus you have shown in (c) to give sufficient data to plot a graph as in (a)(ii),

(ii) show how you would calculate the molality of one of these solutions. [Ar: K, 39.1; Cl, 35.5]

..................................................................................................................................

..................................................................................................................................

..................................................................................................................................

..................................................................................................................................

..................................................................................................................................

..................................................................................................................................

..................................................................................................................................

..................................................................................................................................

..................................................................................................................................

..................................................................................................................................

..................................................................................................................................

..................................................................................................................................

..................................................................................................................................

..................................................................................................................................

..............................................................................................................................[3]

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(e) State a hazard that must be considered when planning the experiment.

..........................................................................................................................................

......................................................................................................................................[1]

(f) State a limiting factor that must be taken into account when increasing the concentration of the aqueous potassium chloride.

..........................................................................................................................................

..........................................................................................................................................

......................................................................................................................................[1]

(g) Draw up a table with appropriate headings to show the data you would record when carrying out your experiments and the values you would calculate in order to construct a graph to support or reject your prediction in (a). The headings should include the appropriate units.

[2]

[Total: 15]

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ForExaminer’s

Use

6

2 When aqueous sodium hydroxide, NaOH, is added to aqueous copper(II) sulfate, CuSO4,a precipitate of copper(II) hydroxide, Cu(OH)2, is produced.

The stoichiometric equation for this reaction is

CuSO4 (aq) + 2NaOH (aq) Cu(OH)2 (s) + Na2SO4 (aq)

An experiment was carried out to investigate this stoichiometry. • A weighed sample of copper(II) sulfate-5-water, CuSO4.5H2O, was completely dissolved

in distilled water. • An excess of aqueous sodium hydroxide was added. • The resultant precipitate was filtered off. • The precipitate was washed thoroughly and completely dried. • The mass of the precipitate was recorded.

(a) Calculate the relative formular mass, Mr, of each of the following. [Ar: Cu, 63.5; S, 32.1; O, 16.0; H, 1.0]

CuSO4.5H2O Cu(OH)2

Mr Mr

[1]

(b) The results of the experiment are recorded below.

A B C D Emass of

CuSO4.5H2O/ g

mass ofCu(OH)2

/ g

2.50 0.78

6.24 1.95

9.99 3.12

14.98 4.20

19.97 6.24

24.96 7.80

29.95 9.36

34.94 11.81

42.43 13.26

Process the results in the table to calculate the number of moles of CuSO4.5H2O used and the number of moles of Cu(OH)2 produced, to enable you to plot a graph to show the relative number of moles of the CuSO4.5H2O and Cu(OH)2.

Record these values to three decimal places in the additional columns of the table.You may use some or all of the columns.

Label the columns you use. For each column you use, include units where appropriate and an expression to show

how your values are calculated. You may use the column headings A to E in your expressions. [2]

(c) Why was it not necessary to know the concentration of the aqueous sodium hydroxide?

..........................................................................................................................................

......................................................................................................................................[1]

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(d) Present the data calculated in (b) in graphical form. Draw the line of best fit.

[3]

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(e) Circle on the graph any point(s) you consider to be anomalous. For any point circled on the graph suggest an error in the conduct of the experiment that

might have led to an anomalous result.

..........................................................................................................................................

..........................................................................................................................................

..........................................................................................................................................

..........................................................................................................................................

..........................................................................................................................................

..........................................................................................................................................

..........................................................................................................................................

......................................................................................................................................[3]

(f) Determine the slope of the graph. Mark clearly on the graph any construction lines and show clearly in your calculation how the intercepts were used in the calculation of the slope.

[3]

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(g) State whether the result in (f) confirms or not the stoichiometry of the equation for the reaction between aqueous copper(II) sulfate and aqueous sodium hydroxide.

..........................................................................................................................................

..........................................................................................................................................

..........................................................................................................................................

..........................................................................................................................................

Comment on your conclusion.

..........................................................................................................................................

..........................................................................................................................................

..........................................................................................................................................

..........................................................................................................................................

..........................................................................................................................................

..........................................................................................................................................[2]

[Total: 15]

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...A acidified aqueous potassium dichromate(VI) B an alkaline solution containing complexed Cu2+...

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