INSTRUCTIONS• Use black ink. You may use an HB pencil for graphs and diagrams.• Complete the boxes above with your name, centre number and candidate number.• Answer all the questions. • Write your answer to each question in the space provided.• Additional paper may be used if required but you must clearly show your candidate

number, centre number and question number(s).

INFORMATION• The total mark for this paper is 60.• The marks for each question are shown in brackets [ ].• Quality of extended responses will be assessed in questions marked with an

asterisk (*).• This document consists of 16 pages. Any blank pages are indicated.

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GCSE (9–1) Combined Science(Chemistry) A (Gateway Science)J250/09 Paper 9, C1–C3 and CS7 (PAGs C1–C5)(Higher Tier)Year 11 TestTime allowed: 1 hour 10 minutes

You must have:• a ruler (cm/mm)• the Data Sheet for GCSE Combined Science A

(Chemistry)

You may use:• a scientific or graphical calculator• a pencil

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OCR is an exempt Charity© OCR 2017 Practice paperDC (SC/SG) 164256/2

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J250/09© OCR 2017 Practice paper

SECTION A

Answer all the questions.

You should spend a maximum of 20 minutes on this section.

1 Which equation shows a physical change?

A CaCO3(s) CaO(s) + CO2(g)

B C(s) + O2(g) CO2(g)

C MgO(s) + H2SO4(aq) MgSO4(aq) + H2O(l)

D H2O(s) H2O(l)

Your answer [1]

2 What is the typical bond length in a molecule, in metres?

A 10–6

B 10–8

C 10–10

D 10–12

Your answer [1]

3 A calcium ion has the formula Ca2+.

A phosphate ion has the formula PO43–.

What is the formula of calcium phosphate?

A CaPO4

B Ca(PO4)3

C Ca2(PO4)3

D Ca3(PO4)2

Your answer [1]

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4 The accurate relative atomic mass of silicon is 28.08553.

What is this number to four significant figures?

A 28.08

B 28.09

C 28.0855

D 28.0856

Your answer [1]

5 The mean mass of an atom of an element is 2.325 × 10–23 g.

The Avogadro constant is 6.022 × 1023 atoms/mol.

What is the element?

A Carbon

B Fluorine

C Nitrogen

D Oxygen

Your answer [1]

6 What is the mass of 2 moles of aluminium nitrate, Al (NO3)3?

A 234 g

B 426 g

C 594 g

D 702 g

Your answer [1]

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J250/09© OCR 2017 Practice paper

7 Calcium Iodide, CaI2, is a solid at room temperature and pressure.

Which type of forces or bonds are broken when calcium iodide changes state?

A Covalent

B Intermolecular

C Ionic

D Metallic

Your answer [1]

8 The table shows bond energy.

Bond Bond energy inkJ/mol

H–H 436

O=O 498

O–H 464

Hydrogen reacts with oxygen to make steam.

2H–H + O=O 2 H–O–H

What is the energy change, in kJ/mol?

A –442

B –486

C +442

D +486

Your answer [1]

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9 Hydrochloric acid is a strong acid.

Some hydrochloric acid has a pH of 2. The acid is diluted by a factor of 1000.

Estimate the pH of the diluted acid.

A 3

B 4

C 5

D 6

Your answer [1]

10 An electric current is passed through an aqueous solution of copper sulfate, CuSO4, using inert electrodes.

Cathode (–) Anode (+)

A copper oxygen

B copper sulfur

C oxygen copper

D sulfur copper

Which row of the table shows the correct products at each electrode?

Your answer [1]

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J250/09© OCR 2017 Practice paper

SECTION B

Answer all the questions.

11 This question is about properties of carbon.

(a) Ethylene glycol is a carbon compound used in antifreeze.

The displayed formula of a molecule of ethylene glycol is shown below.

H H

C C O HOH

H H

Each line represents a covalent bond.

(i) Calculate the relative molecular mass of ethylene glycol.

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(ii) What is the empirical formula for ethylene glycol?

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(b) Carbon atoms form four covalent bonds.

(i) Explain what is meant by a covalent bond in terms of electrons.

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(ii) Why can a carbon atom form four covalent bonds?

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(iii) An organic compound in the same family as ethylene glycol has the molecular formula C3H8O2.

Draw a displayed formula for this molecule.

[1]

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(c) Diamond and graphite are crystalline forms of carbon.

The table shows properties of diamond, graphite and aluminium.

Substance Melting point/°C

Electrical conductivity

Diamond 3550 Poor

Graphite 3652 Very good

Aluminium 2467 Very good

Explain the properties of the substances in the table.

Use the data from the table and your knowledge of structure and bonding.

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12 This question is about atoms and ions of elements in the periodic table.

(a) Elements contain different isotopes.

Define the term isotopes.

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(b) Complete the table for an atom and an ion of two different elements.

Element symbol

Mass number Protons Neutrons Electrons Charge

.................. .................. 11 12 .................. 0

.................. 40 .................. .................. 18 1+

[3]

(c) Sodium oxide is an ionic compound with the formula Na2O. Sodium oxide can be made by reacting sodium with oxygen.

(i) In the reaction, electrons are transferred between sodium and oxygen atoms.

Describe this transfer of electrons.

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(ii) Construct a dot and cross diagram for Na2O.

Show outer electrons only and the charges on each ion.

[2]

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(iii) Construct a balanced equation for the reaction.

Add state symbols.

................ (............) + ................ (............) ................ (............) [3]

(d) Magnesium reacts with nitrogen to form magnesium nitride, which is an ionic compound.

Predict the charge on the nitride ion and suggest the formula of magnesium nitride.

Use the periodic table to help you.

Charge: .....................................................................................................................................

Formula: .............................................................................................................................. [2]

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13 A student wants to make magnesium chloride, MgCl 2.

The student adds magnesium carbonate to hydrochloric acid, HCl.

(a) The equation is shown below.

MgCO3(s) + 2HCl (aq) MgCl 2(aq) + CO2(g) + H2O(l)

(i) Describe a test that would identify the gas that has formed.

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(ii) Calculate the masses of MgCO3 and HCl that react to form 0.0200 mol of MgCl 2.

Mass of MgCO3 = .............. g

Mass of HCl = .............. g [4]

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(b) The student wanted to make sure that all of the HCl had reacted. The student added an excess of magnesium carbonate so that HCl is the limiting reagent.

The student then purified the reaction mixture in two stages to make a dry sample of magnesium chloride.

Explain how the student would obtain pure magnesium chloride from the reaction mixture in two stages.

Include a labelled diagram for the first stage.

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14 A student does some experiments with acids, alkalis and salts.

(a) Experiment 1

• The student measures the temperature of 30 cm3 of 2.0 mol/dm3 hydrochloric acid, HCl.

• The student adds 30 cm3 of 2.0 mol/dm3 sodium hydroxide, NaOH.

• The student measures an increase in temperature of 12 °C.

The equation for the reaction is shown below.

HCl (aq) + NaOH(aq) NaCl (aq) + H2O(l)

(i) Explain whether the reaction is exothermic or endothermic.

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(ii) Draw and label the reaction profile for the reaction.

On your diagram:• Include the formulae of the reactants and products• Label the activation energy A• Label the energy change E.

Energy

Progress of reaction

[3]

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(iii) Calculate the mass of NaOH in 30 cm3 of 2.0 mol/dm3 NaOH.

Answer = .................. g [3]

(iv) The student repeats the experiment but mixes 60 cm3 volumes of 2.0 mol/dm3 hydrochloric acid and 60 cm3 of 2.0 mol/dm3 sodium hydroxide.

The temperature increase is the same as in the first experiment.

Suggest reasons for these observations.

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(b) Experiment 2

• The student add the solution of sodium chloride obtained from Experiment 1 to a beaker.• The student set up the circuit below using inert electrodes.

− +d.c. supply

Cathode Anode

Sodium chloride solution

The student observes gas bubbles at each electrode.

• She is confident that only one gas formed at the cathode• She also concludes that two different gases could have formed at the anode.

Predict the gases at the electrodes and explain the student’s conclusions.

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END OF QUESTION PAPER

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