Igcse Chemistry Revision Guide Answer

7/17/2019 Igcse Chemistry Revision Guide Answer

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C h e m i s t r y R e v i s i o n G u i d e

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Section A: Principles of Chemistry

1 a) electron b) electron

c) proton and neutron d) proton and electron

e) neutron

2 a) metals; non-metals; lost, gained; high; high

b) i) 2.8.2; 2.8.7 ii) 2.8; 2.8.8

3 a) Starting states – B; B; A; C Finishing states – A; C; C; A

b) B

c) element; mixture; mixture; compound

4 a) Atoms that have the same number of protons but different numbers of neutrons.

It is essential to include the word atom in your answer.

Alternative answer

Atoms with same atomic number but different mass numbers, or atoms of the same

element with different masses.

b) i) First row – 37; 48 Second row – 37; 87

ii)(85 ! 71) + (87 ! 28)

100= 85.6

c) They have the same electronic configuration.

Do not mention protons or neutrons in your answer.

Chemical reactions involve only electrons.

Alternative answer

Both have same number of electrons in the outer shell, or both have one electron in

the outer shell.

d) i) Rb2O; RbCl

ii) Any two from: • rubidium fizzes or bubbles or moves around

• rubidium disappears or dissolves

• rubidium melts or forms a ball

• rubidium catches fire or explodes or flame is produced

iii) 2Rb + 2H2O ! 2RbOH + H2

5 a) Electrons within the structure are free to move.

b) Ions cannot move until the lead(II) bromide is a liquid.



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c) First reaction – B and reduction

Second reaction – A and oxidation

d) i) Amount of Pb = 0.05 mol; Amount of Br 2 = 0.05 mol

ii) Mass of bromine = 0.05 x 160 g = 80 g

6 a) i) (39 + 16 + 1) = 56

ii)14.0

56= 0.25 mol

iii) 0.25 !1000

250= 1.0 mol/dm

3

b) i)200

1000! 2.0 = 0.40 mol

ii)1

2! 0.40 = 0.20 mol

iii) 0.20 ! 24 = 4.8 dm3

7 a) Allotropy

Allotropy is no longer on the specification.

b) Covalent. The attraction of each of the two nuclei for a shared pair of electrons.

c) Cutting or drilling.

d)

e) Both are giant structures containing lots of covalent bonds that have to be broken.

It requires a lot of energy to break these bonds.

8 a) The force of attraction between two nuclei and a pair of electrons shared between them.

b) simple; weak; molecules; low.



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c) i)

ii)

9 a) A magnesium atom loses two electrons to form a magnesium ion.

A fluorine molecule/ two fluorine atoms gain two electrons to form two fluoride ions.

b) Magnesium; loss of electrons is oxidation.

c) i) Na+ and F –

ii) NaF

d) Yellow

10 a) NaCl (s) and H2O(l)

b) i) Dilute nitric acid and aqueous silver nitrate.

ii) White precipitate.

iii) Diffusion.

c) i)

ii) (Simple) distillation.

11 a) (56 ! 2) + (16 ! 3) = 160

b) i)320 ! 1000

160= 2000

ii) 2 ! 2000 = 4000

iii) 4000 ! 56 = 224000 g = 224 kg

c) i) It restricts the capacity of the blood to carry oxygen.

ii) 5000!

24 = 120000 dm

3

d) Fe2O3 + 3CO ! 2Fe + 3CO2



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e) i) Silicon dioxide (silica/sand)

ii) CaCO3 ! CaO and CaO + SiO2 ! CaSiO3

12 a) By heating.

b) i) Diffusion

ii) Ammonium chloride (NH4Cl )

iii) Ammonia particles move more quickly

iv) A – red; B – blue

13 a) Distillation

b) Evaporation

c) Filtration / decantation

d) Chromatography

e) Fractional distillation

14 a) i) (1 + 80) = 81

ii)1.62

81= 0.02

iii)0.02

250! 1000 = 0.08

iv) 0.08 x 81 = 6.48

b) i) HBr + NaOH ! NaBr + H2O OR H+ + OH " ! H2O

ii) A proton is transferred from HBr to NaOH / OH "

iii)20.0

1000! 0.20 = 0.004(00)

iv) 20.0 ! 2 = 40.0 cm3

v) Methyl orange – red to orange (allow yellow), OR

Phenolphthalein – colourless to pink (allow red)

15 a) i) Giant lattice of positive ions with delocalised electrons.

ii) Can be beaten or hammered into shape.

iii) The layers of ions can slide over one another.

b) The two fluorine nuclei are attracted to a shared pair of electrons.

c) i) 2.7 ii) 2.8

d)



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16 a) i) Left-hand electrode –; right-hand electrode +

ii) H+; it is gaining electrons

iii) Horizontal line in right-hand tube halfway between the line given and the top of the tube.

The same number of moles of electrons produce twice as many moles of hydrogen as

oxygen.

b) i)0.40

2= 0.20

ii) (0.20 ! 24) = 4.8 dm3

c) i)0.80

4= 0.20

ii) (0.20 ! 32) = 6.4 g




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Section B: Chemistry of the Elements

1 a) Atomic number b) Relative atomic mass

c) Group 1 d) Group 6

e) 3 or 4 or 5

2 a) i) Calcium / Ca2+

ii) Turns limewater milky

iii) Carbonate / CO32

b) i) Fe2+ ii) Iron(II) hyrdoxide

iii) Sulfate / SO42 iv) BaSO4

c) Any two from chloride, bromide and iodide

d) i) CaCO3 ii) FeSO4

3 a) X b) 21

c) Re-lights a glowing spill d) Carbon dioxide

4 a) i) 5 ii) Colourless

b) i) NH3 + HCl ! NH4Cl

OR

NH3 + H+ ! NH4

+

ii) Add sodium hydroxide solution and warm. The gas given off turns damp red litmus paper

blue.

iii) Add 15 cm3 of ammonia solution to 25 cm3 of hydrochloric acid.

Leave the solution to evaporate.

Dry the crystals with filter paper.

c) i) Lead(II) nitrate and any soluble chloride, such as sodium chloride or hydrochloric acid.

ii) Lead(II) nitrate + sodium chloride! Lead(II) chloride + sodium nitrate

5 a) Any two from • bubbles of gas / fizzing / effervescence

• white precipitate / water goes cloudy

• water gets warm

• calcium bobs up and down

Ca + 2H2O! Ca(OH)2 + H2

b) Zinc oxide. Zn + H2O! ZnO + H2

c) i) Zn + Fe2+! Zn2+ + Fe

ii) Displacement / redox

d) Oxygen

e) i) Coat it with zinc



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ii) Zinc is more reactive than iron so corrodes instead of the iron.

6 a) Less than thirteen bubbles in the iron tube. More than thirteen bubbles in the magnesium tube.

b) Zinc + hydrochloric acid! zinc chloride + hydrogen

c) Any one from copper, silver, gold, platinum.

d) Water and oxygen.

7 a) aq; l; g

b) Hydrochloric acid or sulfuric acid or nitric acid

c) Carbonate ion; carbon dioxide

d) i) Calcium hydroxide

ii) Limewater

iii) Limewater turns milky

iv) CaCO3 + H2O

e) Makes it acidic/ lowers its pH to below 7

8 a) i) Any two from • sodium moves around

• bubbles of gas / fizzing / effervescence

• sodium melts / forms a ball

• sodium disappears

ii) Sodium + water!

sodium hydroxide + hydrogeniii) Blue / indigo / violet / purple. The solution is (strongly) alkaline / contains hydroxide ions.

b) i) Yellow

ii) Flame test

c) i) Electrons are transferred from sodium atoms to oxygen atoms. Each sodium atom loses

one electron. Each oxygen atom gains two electrons.

ii) Na+ and O

2

9 a) 2.8.7

b) 7

c) Brown to colourless

d) i) Red. The solution is acidic / hydrobromic acid has been formed / the solution contains

hydrogen ions (H+).

ii) Blue. The solution is not acidic / no hydrogen ions are formed.

10 a) i) 2

ii) 2.8.2

b) i) Any two from • bubbles of gas / fizzing / effervescence



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• white precipitate / water goes cloudy

• water gets warm

• calcium bobs up and down

ii) Ca(OH)2

iii) Blue. The solution is alkaline / contains hydroxide ions.

c) i) Magnesium is silver; magnesium oxide is white.

ii) Upward delivery in air. Over water.

iii) Hydrogen + oxygen! water

11 a) Zinc is less reactive than magnesium.

b) i) Fe + CuSO4 ! FeSO4 + Cu

OR

Fe + Cu2+ ! Fe2+ + Cu

ii) Solid turns from dark grey to pink-brown.

Solution turns from blue to green.

c) Hydrogen is more reactive than copper, but less reactive than iron.

12 a) i) The solid in the flask is calcium carbonate.

The liquid in the tap funnel is dilute hydrochloric acid.

ii) Carbon dioxide is more dense than air. Collect by downward delivery in air or over water.

iii) CaCO3(s) + 2HCl (aq)! CaCl 2(aq) + H2O(l) + CO2(g)

OR

CaCO3(s) + 2H+(aq)! Ca2+(aq) + H2O(l) + CO2(g)

b) Magnesium burns with a white flame. White solid formed.




1

Section C: Organic Chemistry

1 a) They contain only the elements hydrogen and carbon.

b) i) Alkanes

ii) CnH2n+2

iii) A and D

c) i) Compounds that have the same molecular formula but have different displayed formulae.

ii) None of them have isomers.

d)

e) (2 ! 12) + (4 ! 1) = 28

2 a) i) Similar chemical properties and same general formula.

ii) Contains a carbon to carbon double bond (C = C).

b) i) Orange to colourless.

ii)

c)

3 a) i) Reaction 1 – fermentation; Reaction 2 – dehydration.

ii) Addition.

b) Any two from • dissolve the sugar in water

• add yeast

• warm / temperature 25–40°C

• no oxygen / air

c) C2H5OH! C2H4 + H2O



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d)

e)

f) Condensation.

A small molecule, such as water, is also formed along with the polymer.

4 a) i) C or F

ii) A and B

iii) E

b) Poly(ethene) / polythene

5 a) i) It contains oxygen.

ii) CH3

iii) A series of compounds that have the same general formula and similar chemical properties.

iv)

v) Poly(propene) / polypropylene

vi)

vii) Compound E has a carbon to carbon double bond / is unsaturated.

The polymer does not have a carbon to carbon double bond / is saturated.



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b)




1

Section D: Physical Chemistry

1 a) i) s; aq; aq; l; g.

ii) Copper(II) carbonate – green; copper(II) sulfate – blue.

iii) Any one from • copper(II) carbonate disappears

• bubbles of gas / fizzing / effervescence

b) an acid; a carbonate; a salt; neutralisation

c) i) To make sure that all the acid has reacted.

ii) Filtration

d) Allow the solution to evaporate to dryness in a warm room. OR

Heat the solution until it is saturated and then leave to cool and crystallise.

2 a) Zinc + sulfuric acid ! zinc sulfate + hydrogen

b) i) effervescence ii) sloweriii) exothermic

c) Mix the gas with air in a test tube and put a flame at the mouth of the tube. A squeaky pop is

produced.

d) i) Filtration. ii) Barium chloride. A white precipitate.

3 a) Catalyst

b) i) A curve that is steeper that the original curve and which levels off before 30 seconds but

at the same height.

ii) A curve that is less steep than the original one and which levels off at the same height but

after 30 seconds.

c) Re-lights a glowing spill.

4 a)

b) (bonds broken) = (4 ! 412) + (2 ! 496) = 2640 kJ"

(bonds made) = (2 ! 743) + (4 ! 463) = 3338 kJ"

Energy change = (2640 – 3338) = "698 kJ/mol

c) Increase the temperature; increase the pressure / concentration of the gases; add a catalyst.

d) i) reversible reaction; ! H enthalpy change / heat energy change of reaction.

ii) Pressure increased – amounts decrease

Temperature decreased – amounts decreased




1

Section E: Chemistry in Society

1 a) i) Nitrogen – air; hydrogen – natural gas

ii) 450°C and 200 atmospheres pressure

iii) It is liquefied

iv) Re-cycled

b) NH3 + HNO3 ! NH4 NO3

2 a) Bitumen – making roads / making roofs; kerosene – jet aircraft fuel

b) i) Gasoline + oxygen! carbon dioxide + water

ii) Shortage of oxygen / air

iii) Carbon monoxide is produced. Carbon monoxide is poisonous as it reduces the capacity of

blood to carry oxygen.

c) Heat the crude oil in a round-bottomed flask. Use a thermometer to measure the temperature ofthe vapours distilling over and collect those between 80°C and 120°C. Condense the vapours by

passing them through a Liebig condenser.

3 a) Hydrogen and carbon.

b) They condense at different heights according to their different boiling points.

c) Gasoline – petrol for cars; Bitumen – making roads / making roofs.

d) Any two from: refinery gases, kerosene, diesel, fuel oil.

e) i) Carbon dioxide and water

ii) Carbon monoxide is produced. Carbon monoxide is poisonous as it reduces the capacity of

blood to carry oxygen.

4 a) i) Limestone and coke.

ii) Slag / calcium silicate

iii) C(s) + O2(g)! CO2(g)

iv) CO2

b) i) Oxygen and water.

ii) Zinc. The coating of zinc prevents the iron from coming into contact with water and

oxygen.

OR

Zinc is more reactive than iron and therefore corrodes in preference to the iron.

iii) It is coated in oil.

5 a) i) Limestone ii) Coke

iii) Iron ore (in any order) iv) Molten slag

v) Molten iron

b) i) Reaction 1 ii) Carbon dioxide; it loses oxygen



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c) It is poisonous / toxic.

d) It is too reactive / it is more reactive than carbon / it cannot be reduced by carbon monoxide.

6 a) i) Electrolysis ii) Carbon / graphite

iii) A is +; B is " iv) Aluminium oxide and cryolite

v) Electricity

b) i) Oxygen

ii) Carbon dioxide / carbon monoxide. Formed when the electrode reacts with the oxygen

produced.

7 a) Condensation

b) i) Di-amine

ii) Di-carboxylic acid

iii)

c) Low; weak; molecules.




1

Section F: Assessing Investigative/Experimental Skills (A03)

1 a) A – measuring cylinder C – conical flask F – beaker

b) A and E

c) B

2 a) A – measuring cylinder; 8.6 cm3

B – beaker; 100 cm3

C – pipette; 25(.0) cm3

D – burette; 12.30 cm3

b) i) B ii) D

3 a) i) Temperature before = 27.0°C; temperature after = 67.5°C

Temperature change = 40.5°C

ii) The mass of alcohol and burner both before and after burning.

iii) 67.3; 67.2; 66.9

iv) 48.5; 67.1; 70.4; 82.3

b) i) Yes. The temperature change per gram of fuel gives similar results when repeated.

ii) 81.6 is very different to the other two results.

iii) Repeated the experiment and discarded the anomalous results.

c) No. Only alcohols have been tested, not all fuels. Also, only alcohols with up to four carbon

atoms were tested; a bigger range should be tested.

4 a) i) Circled point is (3.95;12.1).

ii) Too much potassium iodide taken so too much precipitate produced.

OR

Precipitate not allowed to stand for long enough so not fully settled.

iii) If no lead(II) nitrate is added, no precipitate will be produced.

b) All of the potassium iodide has been used up.

c) i) 1.5 cm ii) 3.8 cm3

d) i) Take extra results between 6 and 10 cm3 of lead(II) nitrate solution added.

ii) To make it easier to see when the graph line levels off.

e) Filter off the precipitate. Wash it with distilled / deionised water. Dry it on filter paper.

Weigh it.



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5 a) When the acid was added.

b) i) Circled point is (22.5; 5).

ii) The reaction was carried out at a temperature that was too high.

OR

The volumes used were too large so that the depth of liquid was too great.

iii) 7 seconds.

c) 0.143 (s –1)

d) Heat is lost to the surroundings so the recorded temperature is inaccurate.

The time for the reaction to take place is much shorter, therefore there is a greater percentage

error involved in measuring it.

e) i) The rate of reaction increases in a non-linear fashion as the temperature increases.

ii) The particles have gained energy.

More of the collisions have energy greater than the activation energy.

There are more successful collisions per second.

f) Use the same volume of sodium thiosulfate each time.

Vary the volume of hydrochloric acid from one experiment to the next.

Use different volumes of water in each experiment to keep the depth of solution the same each

time.

Keep the temperature constant in each experiment.

6 a) 10.6 g

b) Decreases

c) Work in a fume cupboard. Sulfur dioxide is toxic.

d) i) The water evaporated.

ii) The water evaporated much faster at 90 than at 30.

e) Measure the pH of the solution.

7 a) U and V

b) X and Z

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