AQA GCSE Chemistry Chemistry Paper 1 (Higher), November 2021: Question 5
10 marks · Standard Demand difficulty · Short Answer
Answer questions on the preparation and neutralisation reactions of salts, followed by calculating the volume of chlorine gas reacting with iron.
Practise this questionQuestion
Question text
05 This question is about salts.
05.1 Name the salt produced by the neutralisation of hydrochloric acid with
potassium hydroxide.
[1 mark]
05.2 Write an ionic equation for the neutralisation of hydrochloric acid with
potassium hydroxide.
[1 mark]
+ →
05.3 Soluble salts can be produced by reacting dilute hydrochloric acid with an
insoluble solid.
Copper, copper carbonate and copper oxide are insoluble solids.
Which of these insoluble solids can be used to make a copper salt by reacting the
solid with dilute hydrochloric acid?
[1 mark]
Tick ( ) one box.
Copper and copper carbonate only
Copper and copper oxide only
Copper carbonate and copper oxide only
Copper, copper carbonate and copper oxide15
A student makes crystals of magnesium sulfate.
This is the method used.
1. Add sulfuric acid to a beaker.
2. Warm the sulfuric acid.
*14* 3. Add a spatula of magnesium oxide to the beaker.
4. Stir the mixture.
5. Repeat steps 3 and 4 until there is magnesium oxide remaining in the beaker.
6. Filter the mixture.
7. Evaporate the filtrate gently until crystals start to form.
8. Leave the solution to finish crystallising.
05.4 Give one reason for:
• step 2
• step 5
• step 6.
[3 marks]
Step 2
Step 5
Step 6
05.5 How should the filtrate be evaporated gently in step 7?
[1 mark]
05.6 Iron chloride is produced by heating iron in chlorine gas.
The equation for the reaction is:
2Fe + 3Cl2 → 2FeCl3
Calculate the volume of chlorine needed to react with 14 g of iron.
You should calculate:
• the number of moles of iron used
• the number of moles of chlorine that react with 14 g of iron
• the volume of chlorine needed.
Relative atomic mass (Ar): Fe = 56
The volume of 1 mole of gas = 24 dm3
[3 marks]
Volume of chlorine = dm3
Mark scheme
Show the mark scheme
Question 5
AO /
Question Answers Extra information Mark
Spec. Ref.
05.1 potassium chloride allow KCl 1 AO1
4.4.2.2
AO /
Spec. Ref.
H+ + OH− → H O
05.2 2 ignore state symbols 1 AO1
4.1.1.1
4.4.2.4
AO /
Spec. Ref.
05.3 copper carbonate and copper 1 AO1
oxide only 4.4.1.2
4.4.2.2
4.4.2.3
RPA1
AO /
Spec. Ref.
05.4 (Step 2) to speed up the 1 AO1
reaction 4.4.2.3
RPA1
(Step 5) to make sure all the 1
(hydrochloric) acid reacts
(Step 6) to remove the excess ignore to remove impurities 1
magnesium oxide
AO /
Spec. Ref.
05.5 using a (boiling) water bath 1 AO1
or 4.4.2.3
using an electric heater – HEMISTRY – –
RPA1
Question 5 continued
AO /
Spec. Ref.
16 05.6 14 1 AO2
(moles Fe = =) 0.25 (mol)
56 4.3.2.1
4.3.2.2
3 allow correct use of an 1 4.3.5
(moles Cl2 = 2 × 0.25 =) 0.375
incorrectly calculated number of
(mol)
moles of Fe
(volume Cl2 = 24 × 0.375) allow correct use of an 1
= 9.0 (dm3) incorrectly calculated number of
moles of Cl2
Total 10
How to answer it
AQA GCSE Chemistry: Making Salts & Gas Calculations
What this question tests
This question assesses core understanding from Topic 4 (Chemical Changes) and quantitative skills from Topic 3 (Quantitative Chemistry):
- Naming salts produced in acid-alkali neutralisations.
- Writing the universal ionic equation for neutralisation reactions.
- Understanding metal reactivity with dilute acids (metals below hydrogen vs bases/carbonates).
- Required Practical 1 (RPA 1): Step-by-step reasoning for preparing a pure, dry soluble salt from an insoluble oxide/base.
- Safe methods of gentle evaporation during crystallisation.
- Stoichiometric calculations linking reacting mass, molar ratios, and molar gas volume (24 dm³ rule).
Naming the Salt Produced
Neutralisation of hydrochloric acid with potassium hydroxide [1 mark]
✅ Correct Answer
potassium chloride (or KCl )
💡 Key Knowledge
- The first part of the salt name comes from the metal in the base/alkali: potassium.
- The second part comes from the acid:
• Hydrochloric acid → chloride
• Sulfuric acid → sulfate
• Nitric acid → nitrate
Universal Ionic Equation for Neutralisation
Writing the neutralisation reaction [1 mark]
✅ Correct Answer
H⁺ + OH⁻ → H₂O
🧠 Exam Technique
This is a standard recall question! Whenever an exam asks for the ionic equation for neutralisation between any strong acid and alkali, the answer is always:
H⁺(aq) + OH⁻(aq) → H₂O(l)
The spectator ions (here, K⁺ and Cl⁻) remain unchanged in solution and cancel out.
Selecting Insoluble Solids to Form a Copper Salt
Reactivity with dilute hydrochloric acid [1 mark]
✅ Correct Answer
Tick: Copper carbonate and copper oxide only (Box 3)
❌ Common Error
Many students incorrectly choose options containing copper metal. Remember the reactivity series:
- Copper is less reactive than hydrogen, so pure copper metal will not react with dilute acids to produce hydrogen gas.
- Copper oxide (a base) and copper carbonate (a carbonate) both react readily with dilute acids.
Required Practical 1: Explaining Method Steps
Reasons for steps in making magnesium sulfate crystals [3 marks]
✅ Mark Scheme Answers
- Step 2 (warm acid): To speed up the reaction / increase the rate of reaction.
- Step 5 (add until solid remains): To make sure all the acid reacts / has been neutralised.
- Step 6 (filter mixture): To remove the excess (unreacted) magnesium oxide.
❌ Examiner Pitfalls & Lost Marks
- Step 2: Do NOT say "to melt the magnesium oxide" or "to boil the acid" – warming supplies thermal energy to increase collision frequency.
- Step 5: Do NOT simply say "to make sure it reacts". You must specify that all the acid reacts, ensuring no unreacted acid remains to make the crystals hazardous/impure.
- Step 6: The mark scheme notes: ignore to remove impurities . The filtered solid is specifically the excess unreacted magnesium oxide.
Safe Evaporation in Crystallisation
How to evaporate filtrate gently [1 mark]
✅ Correct Answer
Either of the following:
- Using a (boiling) water bath
- Using an electric heater / heating mantle
🧠 Exam Technique
Direct heating with an open Bunsen burner flame can overheat the salt solution, causing it to "spit" dangerously or decompose the hydrated salt crystals. Placing the evaporating dish over a beaker of boiling water provides gentle, controlled, indirect heating.
Quantitative Chemistry: Gas Volume Calculation
Calculate volume of chlorine needed to react with 14 g of iron [3 marks]
📐 Step-by-Step Calculation Breakdown
Balanced equation: 2Fe + 3Cl₂ → 2FeCl₃
Formula: Moles = Mass ÷ Aᵣ
Moles of Fe = 14 ÷ 56 = 0.25 mol
From the balanced equation, the ratio is 2 Fe : 3 Cl₂
Moles of Cl₂ = 0.25 × (3 ÷ 2) = 0.25 × 1.5 = 0.375 mol
Formula: Volume (dm³) = Moles × 24 dm³
Volume of Cl₂ = 0.375 × 24 = 9.0 dm³ (or 9 dm³)
❌ Common Errors in this Calculation
- Ignoring the 2:3 ratio: Assuming a 1:1 ratio gives 0.25 mol of Cl₂, leading to an incorrect volume of 6 dm³.
- Inverting the ratio: Multiplying by 2/3 instead of 3/2. Always check: more moles of Cl₂ are needed than Fe!
- Trying to find the mass of Cl₂: You do NOT need the Mᵣ of Cl₂ here because the question gives molar gas volume (24 dm³). Just multiply moles directly by 24.
🧠 Exam Checklist for Gas Volumes
- Check units: The answer line asks for dm³, and the constant is given as 24 dm³. No unit conversion needed.
- Follow the question prompts: The bullet points explicitly guide you through the three exact steps required!
Topics
Chemistry · Required Practicals · C4: Chemical Changes · Required Practicals · C3: Quantitative Chemistry
Question and mark scheme from the AQA GCSE Chemistry examination, Chemistry Paper 1 (Higher), November 2021. QuestionVault is an independent revision resource; questions remain the copyright of the awarding body.