AQA GCSE Chemistry Chemistry Paper 1 (Higher), 2022: Question 4

10 marks · Standard Demand difficulty · Short Answer

Analyze reactions of zinc, including the preparation of zinc chloride crystals, displacement reactions with ionic equations, and drawing a simple chemical cell.

Practise this question

Question

An exam question about zinc and its compounds. It includes questions on reacting zinc oxide with hydrochloric acid to make zinc chloride crystals, completing an ionic equation for the displacement reaction between zinc and copper chloride, explaining why zinc is oxidised, and completing a diagram of a simple chemical cell using zinc, copper, and an electrolyte to light a lamp.
Question text

04 This question is about zinc and compounds of zinc.

A student produces pure crystals of zinc chloride by reacting zinc oxide with

hydrochloric acid.

The equation for the reaction is:

ZnO(s) + 2HCl(aq) → ZnCl2(aq) + H2O(l)

04.1 The student adds zinc oxide to hydrochloric acid until the zinc oxide is in excess.

Give one observation that the student could make to show that the zinc oxide is

in excess.

[1 mark]

04.2 Why is excess zinc oxide used rather than excess hydrochloric acid?

[1 mark]

04.3 Name one other compound that the student could add to hydrochloric acid to produce

zinc chloride.

[1 mark]

04.4 Describe how the student should obtain crystals of zinc chloride from a solution of

zinc chloride.

[2 marks]

Zinc chloride is also produced in a displacement reaction between zinc and

copper chloride solution.

The equation for the reaction is:

Zn + CuCl2 → ZnCl2 + Cu

04.5 Complete the ionic equation for this reaction.

[1 mark]

Zn + … → Zn2+ + …

04.6 Why is zinc described as being oxidised in this reaction?

[1 mark]

04.7 Zinc and copper can be used with another substance to produce electricity.

Complete Figure 7 to show how zinc, copper and another substance can be used to

light a lamp.

Label:

• zinc

• copper

• the other substance used.

The symbol represents the lamp.

[3 marks]

Figure 7

Mark scheme

Show the mark scheme The mark scheme for Question 4. It lists the accepted answers: 4.1 accepts 'solid remaining'; 4.2 accepts 'excess zinc oxide can be filtered off'; 4.3 accepts 'zinc hydroxide' or 'zinc carbonate'; 4.4 requires heating to crystallisation point and leaving to cool/crystallise; 4.5 requires completing the ionic equation as Zn + Cu2+ -> Zn2+ + Cu; 4.6 states zinc atoms lose electrons; 4.7 shows a diagram of a beaker containing an electrolyte with a zinc electrode and copper electrode connected in a circuit with a lamp.

Question 4

AO /

Question Answers Extra information Mark

Spec. Ref.

04.1 (zinc oxide) solid remaining allow (zinc oxide) solid no longer 1 AO1

disappears 4.2.2.2

4.4.2.2

4.4.2.3

ignore references to colour / RPA 1

effervescence

AO /

Spec. Ref.

allow converse statements for

04.2 hydrochloric acid AO1

4.4.2.2

(excess) zinc oxide can be allow separation / removal of 1 4.4.2.3

filtered off (excess) zinc oxide is easier RPA 1

ignore to ensure all the

(hydrochloric) acid is used up

AO /

Spec. Ref.

04.3 any one from: 1 AO1

• zinc hydroxide allow Zn(OH)2 4.4.2.2

• zinc carbonate allow ZnCO3 4.4.2.3

RPA1

AO /

Spec. Ref.

04.4 heat (the solution) until allow heat (the solution) until 1 AO1

crystallisation point is reached crystals start to form 4.4.2.3

allow heat (the solution) to RPA 1

reduce the volume

allow heat (the solution) to

evaporate (some of the water)

leave the solution (to cool / 1 15

crystallise)

if no other mark is awarded

allow 1 mark for heat the

solution to dryness

AO /

Spec. Ref.

Zn + Cu2+ → Zn2+ + Cu ignore state symbols 1 AO2

04.5

4.4.1.2

4.4.1.4

AO /

Spec. Ref.

04.6 zinc (atoms) lose (2) electrons do not accept references to 1 AO2

oxygen 4.4.1.2

4.4.1.4

AO /

Spec. Ref.

ignore voltmeter / ammeter

04.7 regardless of location AO1

(a diagram showing) 4.5.2.1

solution in a container ignore labels 1

zinc electrode ignore polarities on electrodes 1

and

copper electrode

16 both inserted into solution

complete circuit that would allow a named electrolyte in 1

function as an electrochemical solution

cell including a labelled allow a named molten

electrolyte electrolyte

do not accept cell / battery in

external circuit

do not accept a wire between

the electrodes

an answer of

scores 3 marks

Total Question 4 10

How to answer it

Zinc, Salts, Redox and Electrochemical Cells

What this question tests

This question assesses core knowledge from AQA GCSE Chemistry Topic 4 (Chemical Changes). It covers the Required Practical 1 (making a soluble salt), writing ionic equations for displacement reactions, defining oxidation in terms of electron transfer, and drawing a functional chemical cell to generate electricity.

Questions 04.1 & 04.2

Reacting Zinc Oxide with Hydrochloric Acid

Adding Reactants in Excess

Correct Answers

04.1: Zinc oxide solid stops disappearing (or solid remains at the bottom of the beaker).

04.2: Excess zinc oxide is an insoluble solid, so it can easily be filtered off to leave a pure solution.

1 Mark each

Key Knowledge

  • Excess reactant: Adding more than is needed ensures that 100% of the limiting reactant (hydrochloric acid) is completely used up.
  • State symbols: ZnO(s) is a solid, while HCl(aq) is aqueous. Once the acid is gone, any extra solid ZnO simply sits at the bottom.

Exam Technique

When asked for an observation, describe what you would actually see. Do not just write "the reaction stops"—explain how you know it has stopped (e.g., "unreacted solid is visible").

Common Errors

  • ❌ Saying "bubbles stop" for 04.1. Zinc oxide is a base, not a carbonate, so no gas/carbon dioxide is produced!
  • ❌ Stating that excess acid is used because "acid is easy to evaporate". Acid is dangerous to evaporate and cannot be easily filtered!
Question 04.3

Alternative Reactants to Make Zinc Chloride

Choosing the Right Reagent

Correct Answers

Any one of the following:

  • Zinc hydroxide / Zn(OH)₂
  • Zinc carbonate / ZnCO₃
  • Zinc metal / Zn
1 Mark

Key Knowledge

To make a soluble salt (Zinc Chloride) from Hydrochloric Acid, you can react the acid with:

  • Metal + Acid → Salt + Hydrogen
  • Metal Oxide + Acid → Salt + Water
  • Metal Hydroxide + Acid → Salt + Water
  • Metal Carbonate + Acid → Salt + Water + Carbon Dioxide
Question 04.4

Obtaining Pure Crystals (Crystallisation)

From Solution to Dry Crystals

Correct Answers

Step 1: Heat the solution until the crystallisation point is reached (or to evaporate some of the water / reduce the volume by half).

Step 2: Leave the remaining solution to cool and crystallise slowly.

2 Marks

Exam Technique

To get both marks, you must show you understand that slow cooling produces crystals. Do not write "heat until all water evaporates" as this produces a dry powder, not nice crystals!

Common Errors & Examiner Warning

Students often lose a mark by saying "heat the solution until dry". The mark scheme only awards 1 mark max if you suggest heating to dryness, because this decomposes the salt and prevents large, pure crystals from forming.

Questions 04.5 & 04.6

Displacement & Redox Equations

Ionic Equations and Electron Transfer

Correct Answers

04.5 Ionic Equation:

Zn + Cu²⁺ → Zn²⁺ + Cu

04.6 Why Zinc is Oxidised:

Zinc atoms lose electrons (specifically, each zinc atom loses 2 electrons).

1 Mark each

Key Knowledge

Remember the mnemonic OIL RIG:

  • Oxidation Is Loss (of electrons)
  • Reduction Is Gain (of electrons)

In this reaction, neutral zinc atoms ( Zn ) become positive ions ( Zn²⁺ ) by losing negative electrons.

Common Errors

  • ❌ Writing that zinc "gains oxygen". While oxidation historically meant gaining oxygen, in this ionic context, it must be defined in terms of electrons.
  • ❌ Confusing the charges in the ionic equation (e.g., writing Cu⁺ instead of Cu²⁺ ).
Question 04.7

Drawing a Chemical Cell

Generating Electricity

How to Draw the Diagram (3 Marks)

Your completed diagram must show:

  1. A container (beaker) holding a liquid solution.
  2. Two separate metal electrodes (one labelled zinc, the other labelled copper) dipping into the solution.
  3. A complete circuit connecting the two electrodes to the lamp, with the electrodes immersed in a labelled electrolyte (e.g., sodium chloride solution or copper sulfate solution).
3 Marks

Diagram Description for Revision

Imagine a beaker filled with liquid. Two vertical rectangular blocks (the electrodes) hang into the liquid. One is labelled "Zinc electrode", the other "Copper electrode". The liquid is labelled "Electrolyte". Wires run from the top of each electrode up to the circle with an 'X' (the lamp), forming a complete loop.

Critical Mistakes to Avoid

  • ❌ Do NOT add a battery or cell symbol to the circuit. The zinc, copper, and electrolyte are the cell. Adding another battery is incorrect!
  • ❌ Do not draw a wire directly connecting the two electrodes underwater (this causes a short circuit). They must only connect through the external wires and lamp.
  • ❌ Do not forget to label the liquid as an electrolyte (or name a specific salt solution). Leaving the liquid unlabelled loses a mark.

Topics

Chemistry · Required Practicals · Required Practicals · C4: Chemical Changes · C5: Energy Changes

Question and mark scheme from the AQA GCSE Chemistry examination, Chemistry Paper 1 (Higher), 2022. QuestionVault is an independent revision resource; questions remain the copyright of the awarding body.