AQA GCSE Chemistry Chemistry Paper 1 (Foundation), June 2023: Question 11

8 marks · Standard Demand difficulty · Extended Answer

Plan a method to make pure, dry crystals of zinc chloride from zinc carbonate and a dilute acid, and name two alternative substances that could react with acid to form zinc chloride.

Practise this question

Question

Question 11 consists of two parts. Part 11.1 asks students to plan a method to make pure, dry crystals of zinc chloride from zinc carbonate and a dilute acid for 6 marks, followed by multiple blank lines. Part 11.2 asks to name two other substances that can each be reacted with a dilute acid to make zinc chloride, instructing not to refer to zinc carbonate, worth 2 marks with two numbered answer lines.
Question text

11 This question is about making a soluble salt.

11.1 Plan a method to make pure, dry crystals of zinc chloride from zinc carbonate and a

dilute acid.

[6 marks]

11.2 Name two other substances that can each be reacted with a dilute acid to make

zinc chloride.

Do not refer to zinc carbonate in your answer.

[2 marks]

Mark scheme

Show the mark scheme Mark scheme for Question 11. Part 11.1 uses a 3-level mark scheme for 6 marks, detailing indicative content: using hydrochloric acid, adding zinc carbonate until in excess, filtering off excess solid, heating filtrate to crystallisation point, and drying crystals with filter paper. Part 11.2 provides 2 marks for any two of zinc, zinc oxide, or zinc hydroxide (formulae Zn, ZnO, Zn(OH)2 allowed). Total marks: 8.

AO/

Question Answers Mark

Spec. Ref

Level 3: The method would lead to the production of a valid AO1

11.1 5–6

outcome. The key steps are identified and logically sequenced. 4.4.2.2

4.4.2.3

Level 2: The method would not necessarily lead to a valid RPA1

outcome. Most steps are identified, but the method is not fully 3–4

logically sequenced.

Level 1: The method would not lead to a valid outcome. Some

1–2

relevant steps are identified, but links are not made clear.

No relevant content 0

Indicative content

• use zinc carbonate and hydrochloric acid

• add zinc carbonate to the (hydrochloric) acid

• in a beaker

• stir

• continue adding until the zinc carbonate is in excess

• shown by excess solid

• and no more effervescence

• filter (the reaction mixture)

• to remove the excess zinc carbonate

• heat the solution

• using a water bath or electric heater

• to crystallisation point

• leave the solution to crystallise

• pat crystals dry with filter paper

AO /

Question Answers Extra information Mark

Spec. Ref.

11.2 any two from: 2 AO2

• zinc allow Zn 4.4.2.3

• zinc oxide allow ZnO

• zinc hydroxide allow Zn(OH)2

Total Question 11 8

How to answer it

Preparation of a Pure, Dry Soluble Salt (Zinc Chloride)

📌 What this question tests

This question assesses practical skills from AQA Required Practical 1 (Making Salts) and knowledge of acids, bases, and neutralisation:

  • Planning an experimental procedure to make a pure, dry sample of a soluble salt from an insoluble carbonate.
  • Understanding why reactants are added in excess and how excess solid is separated by filtration.
  • Crystallisation and drying techniques for obtaining clean crystals.
  • Recalling which general types of substances (metals, metal oxides, metal hydroxides) react with acids to form salts.
Question 11.1 · 6 Marks

Plan a method to make pure, dry crystals of zinc chloride

Required Practical 1: Insoluble Base / Carbonate Method

✅ Full-Mark Model Method (Sequenced & Valid)

  1. Select the correct acid: Measure dilute hydrochloric acid into a beaker.
  2. React: Add zinc carbonate solid to the acid and stir with a glass rod.
  3. Ensure complete reaction: Continue adding zinc carbonate in excess until solid remains at the bottom and fizzing (effervescence) stops.
  4. Filter: Filter the mixture using filter paper and a funnel to remove the unreacted excess zinc carbonate.
  5. Evaporate partially: Pour the zinc chloride filtrate into an evaporating basin and heat gently using a water bath (or electric heater) until the crystallisation point is reached (when crystals start to form at the edge).
  6. Crystallise & Dry: Remove from heat and leave in a warm place to crystallise slowly. Pat the crystals dry using filter paper (or leave to dry in a desiccator / warm oven).

💡 Key Scientific Knowledge

  • Naming the acid: To make a chloride salt, you must name hydrochloric acid (HCl).
  • Why use excess? Adding excess insoluble solid ensures that all the acid is used up and neutralised. If acid remained, the crystals would not be pure.
  • Equation:
    ZnCO₃(s) + 2HCl(aq) → ZnCl₂(aq) + H₂O(l) + CO₂(g)
  • Observation: Effervescence is due to carbon dioxide gas (CO₂). When fizzing stops, all acid is consumed.
  • Gentle heating: Never evaporate to complete dryness with a direct flame, as zinc chloride can thermally decompose or spit dangerously.

🧠 Exam Technique (Level-Marking Strategy)

  • Level 3 (5–6 marks): The method leads to a valid outcome. The key stages are identified and logically ordered: Reacting (in excess) → Filtering → Heating to crystallisation point → Drying.
  • Level 2 (3–4 marks): Most steps are identified, but sequence errors exist (e.g., forgetting to filter before heating, or omitting the name of hydrochloric acid).
  • Level 1 (1–2 marks): Isolated correct points (e.g., just mentions "filter" and "evaporate").
  • Always state the specific apparatus: Mention a beaker, filter funnel + paper, evaporating basin, and water bath to show full practical competence.

❌ Common Examiner Traps & Lost Marks

  • Wrong acid named: Writing sulfuric acid (makes zinc sulfate) or nitric acid (makes zinc nitrate). You must specify hydrochloric acid.
  • Heating to complete dryness: Stating "boil until all water has gone" loses marks for the crystallisation step. Stop at the crystallisation point!
  • Forgetting to specify "excess": Just saying "add zinc carbonate" is not enough; you must explain that you add it until it is in excess and how to tell (no more fizzing / solid remains).
  • Skipping filtration: Forgetting to filter the excess solid before crystallising means your product will be contaminated with unreacted zinc carbonate.
Mark Scheme Breakdown: Indicative content includes naming hydrochloric acid, adding zinc carbonate in excess (stirring in a beaker, until no more fizzing), filtering off excess solid, heating to crystallisation point using a water bath, and drying crystals with filter paper.
Question 11.2 · 2 Marks

Other Substances to Make Zinc Chloride

Reactions of Dilute Acids

✅ Correct Answers (Any TWO from)

  • Zinc (metal) — allow Zn
  • Zinc oxide (metal oxide / base) — allow ZnO
  • Zinc hydroxide (metal hydroxide / alkali) — allow Zn(OH)₂

Each correct substance earns 1 mark (maximum 2 marks).

💡 General Word Equations

  • Metal + Acid → Salt + Hydrogen:
    Zn + 2HCl → ZnCl₂ + H₂
  • Metal oxide + Acid → Salt + Water:
    ZnO + 2HCl → ZnCl₂ + H₂O
  • Metal hydroxide + Acid → Salt + Water:
    Zn(OH)₂ + 2HCl → ZnCl₂ + 2H₂O

❌ Common Errors to Avoid

  • Ignoring the restriction: The question explicitly says: "Do not refer to zinc carbonate in your answer." Writing zinc carbonate scores 0.
  • Naming another acid: Suggesting "hydrochloric acid" scores 0 because the question asks for the substance that reacts with the acid.
  • Writing incorrect formulae: If writing chemical formulae instead of names, make sure valencies are correct: write Zn(OH)₂ , not ZnOH .

🧠 Quick Revision Tip: The Acid Rule Summary

Commit these four general reactions to memory; they frequently appear across paper 1:

  • Acid + Metal → Salt + Hydrogen
  • Acid + Metal Oxide → Salt + Water
  • Acid + Metal Hydroxide → Salt + Water
  • Acid + Metal Carbonate → Salt + Water + Carbon Dioxide
Mark Scheme Breakdown: 1 mark for each correct named zinc compound/metal (maximum 2). Accept names or correct chemical formulae.

Topics

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

Question and mark scheme from the AQA GCSE Chemistry examination, Chemistry Paper 1 (Foundation), June 2023. QuestionVault is an independent revision resource; questions remain the copyright of the awarding body.