AQA GCSE Chemistry Chemistry Paper 1 (Foundation), November 2021: Question 6

9 marks · Low Demand difficulty · Short Answer

Investigate the reaction of copper carbonate with acid by measuring gas volume, calculating graph gradient, and preparing copper chloride crystals.

Practise this question

Question

The question presents an investigation into reacting copper carbonate with acid using a conical flask attached to a gas syringe. Figure 9 shows a reading on a gas syringe between 40 and 50 cm³, requiring reading the volume. Figure 10 shows a straight-line graph of volume of gas in cm³ against mass of copper carbonate in grams from (0.1, 20) to (0.5, 90), with prompts to calculate change in y, change in x, and the gradient. Multiple-choice questions follow regarding which acid produces copper chloride, identifying the gas produced, the purpose of gentle heating (to evaporate water), and an open question on how to heat the solution gently.
Question text

06 This question is about metal carbonates.

A student investigated the reaction of copper carbonate with an acid.

Figure 8 shows the apparatus.

Figure 8

This is the method used.

1. Pour 25 cm3 of the acid into a conical flask.

2. Weigh 0.10 g of copper carbonate.

3. Remove the stopper and add the copper carbonate to the flask.

4. Quickly replace the stopper.

5. Record the maximum volume of gas collected in the gas syringe.

6. Repeat steps 1 to 5 with different masses of copper carbonate.

06.1 Figure 9 shows the gas syringe during the experiment.

Figure 9

What is the reading on the gas syringe?

[1 mark]

23 3

cm

06.2 The student plotted the results on a graph.

Figure 10 shows the student’s graph.

Figure 10

Determine the gradient of the line of best fit.

You should:

• calculate the values of the change in y and the change in x

• calculate the gradient of the line of best fit.

[4 marks]

Change in y = cm3

Change in x = g

Gradient

24 cm3/g

Gradient =

06.3 Copper chloride was produced in the reaction.

Which acid reacts with copper carbonate to produce copper chloride?

*23* [1 mark]

Tick ( ) one box.

Hydrochloric acid

Nitric acid

Sulfuric acid

06.4 The reaction between copper carbonate and the acid produced a gas.

What was the gas?

[1 mark]

Tick ( ) one box.

Carbon dioxide

Chlorine

Hydrogen

Oxygen 25

A different student produced a pure, dry sample of copper chloride using the

same reaction.

This is the method used.

1. Add excess copper carbonate to the acid.

2. Filter the mixture.

3. Heat the solution gently until crystals start to form.

4. Leave for 24 hours.

5. Remove the crystals.

6. Rinse with water and dry the crystals.

06.5 Why was the solution heated gently in step 3?

[1 mark]

Tick ( ) one box.

To evaporate acid

To evaporate copper carbonate

To evaporate water

06.6 How should the solution be heated gently in step 3?

[1 mark]

Mark scheme

Show the mark scheme Mark scheme for Question 6: 06.1 awards 1 mark for 48 cm³. 06.2 awards 4 marks: 1 for change in y = 70, 1 for change in x = 0.4, 1 for gradient = 70/0.4, and 1 for 175 cm³/g. 06.3 gives 1 mark for hydrochloric acid. 06.4 gives 1 mark for carbon dioxide. 06.5 gives 1 mark for 'to evaporate water'. 06.6 gives 1 mark for using a boiling water bath or an electric heater. Total marks: 9.

Question 6

AO /

Question Answers Extra information Mark

Spec. Ref.

06.1 48 (cm3) 1 AO2

4.4.2.2

AO /

Spec. Ref.

06.2 (change in y =) 70 (cm3) 1 AO2

4.4.2.2

(change in x =) 0.4 (g) 1

70 allow correct use of incorrectly 1

(gradient =)

0.4

derived values for change in y

and / or change in x

= 175 (cm3/g) 1

AO /

Spec. Ref.

06.3 hydrochloric acid 1 AO2

4.4.2.2

AO /

Spec. Ref.

06.4 carbon dioxide 1 AO1

4.4.2.2

Question 6 continued

AO /

Spec. Ref.

06.5 to evaporate water 1 AO1

4.4.2.3

RPA1

AO /

Spec. Ref.

06.6 using a (boiling) water bath 1 AO1

or 4.4.2.3

using an electric heater

18 RPA1

Total 9

How to answer it

Reactions of Metal Carbonates & Making Pure Salts

What this question tests

This question assesses key practical competencies and conceptual understanding from AQA GCSE Chemistry Paper 1 (Topic 4: Chemical Changes & Required Practical 1):

  • Reading quantitative laboratory equipment accurately (gas syringe scales).
  • Determining the gradient of a linear graph using Δy / Δx with data points.
  • Naming salts produced from acid-base reactions (hydrochloric acid → chloride).
  • Recalling the general equation: metal carbonate + acid → salt + water + carbon dioxide .
  • Explaining procedural steps in salt preparation, especially controlled gentle evaporation and crystallization.

Question 06.1 (1 Mark)

Reading a Gas Syringe

✅ Correct Answer

48 cm³

Mark Scheme: 48 (cm³) [1 mark, AO2]

🧠 Exam Technique: Scale Divisions

  • Find major divisions: 40 to 50 is a difference of 10 cm³ .
  • Count sub-divisions: There are 5 intervals between 40 and 50. Each small line represents 10 ÷ 5 = 2 cm³ .
  • Locate plunger position: The front vertical line of the plunger sits 4 small marks past 40 → 40 + (4 × 2) = 48 cm³ .

❌ Common Errors

  • Assuming each small mark is 1 cm³ , leading to an incorrect reading of 44 cm³ .
  • Reading the back edge of the plunger rather than the front sealing edge.

Question 06.2 (4 Marks)

Determining the Gradient from a Graph

📐 Step-by-Step Calculation

  1. Find Change in y (Volume of gas in cm³):
    Read coordinates shown by the arrows: from y₁ = 20 to y₂ = 90 .
    Change in y = 90 - 20 = 70 cm³ [1 Mark]
  2. Find Change in x (Mass of copper carbonate in g):
    Read coordinates shown by the arrows: from x₁ = 0.10 to x₂ = 0.50 .
    Change in x = 0.5 - 0.1 = 0.4 g [1 Mark]
  3. Substitute into Gradient Formula:
    Gradient = (Change in y) ÷ (Change in x) = 70 ÷ 0.4 [1 Mark]
  4. Calculate Final Answer:
    70 ÷ 0.4 = 175 cm³/g [1 Mark]

🧠 Exam Technique: Error Carried Forward (ecf)

Always write down your values for Change in y and Change in x explicitly on the answer lines provided. Even if you misread a value from the graph, the mark scheme allows error carried forward for dividing your y-value by your x-value correctly!

❌ Common Calculation Traps

  • Inverting the gradient: Calculating Δx ÷ Δy (0.4 ÷ 70) instead of Δy ÷ Δx .
  • Reading single points: Using a single point like 90 ÷ 0.5 = 180 . The line does not pass through (0,0), so you must calculate differences!

Questions 06.3 & 06.4 (2 Marks)

Acid-Carbonate Reactions & Gas Identification

✅ Question 06.3: Correct Acid

Hydrochloric acid [1 Mark]

Produces a chloride salt:
CuCO₃ + 2HCl → CuCl₂ + H₂O + CO₂

✅ Question 06.4: Gas Produced

Carbon dioxide [1 Mark]

Metal carbonate + acid always liberates carbon dioxide gas ( CO₂ ).

💡 Key Knowledge: Naming Salts

  • Hydrochloric acid ( HCl ) makes chlorides.
  • Sulfuric acid ( H₂SO₄ ) makes sulfates.
  • Nitric acid ( HNO₃ ) makes nitrates.

❌ Common Errors

  • Selecting Hydrogen for 06.4: Students confuse metal + acid reactions (which make H₂) with metal carbonate + acid reactions (which make CO₂ and H₂O).
  • Selecting Chlorine: Salt names ending in -ide do not produce elemental chlorine gas in acid reactions.

Questions 06.5 & 06.6 (2 Marks)

Required Practical 1: Preparing a Pure, Dry Salt Sample

✅ Question 06.5: Purpose of Heating Gently

To evaporate water [1 Mark]

Water is the solvent in aqueous copper chloride; evaporating it concentrates the solution so crystallization can take place.

✅ Question 06.6: Method for Gentle Heating

Any one of the following [1 Mark]:

  • Using a (boiling) water bath
  • Using an electric heater / hot plate

💡 Key Knowledge: Crystallization Method

  • Step 1 adds excess carbonate to ensure all acid is fully neutralised.
  • Step 2 filters to remove unreacted solid copper carbonate.
  • Step 3 heats gently only until crystals start to form at the edge (the point of crystallisation). It is NOT boiled dry!
  • Step 4 allows the remaining liquid to cool and slowly form large crystals.

🧠 Exam Technique: "Gently" in Lab Science

When an examiner specifies heating gently or safely without thermal decomposition, direct heating with a roaring Bunsen flame is never correct. Always state a water bath or electric heating mantle/plate for uniform, controlled temperature.

Topics

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

Question and mark scheme from the AQA GCSE Chemistry examination, Chemistry Paper 1 (Foundation), November 2021. QuestionVault is an independent revision resource; questions remain the copyright of the awarding body.