AQA GCSE Combined Science: Trilogy Chemistry Paper 1 (Foundation), 2021: Question 2

8 marks · Standard Demand difficulty · Short Answer

This multi-part question assesses understanding of the electrolysis of copper chloride solution, including ion movement, products at electrodes, and a calculation of mass in a given volume of solution.

Practise this question

Question

The image contains a series of sub-questions labeled 02.1 through 02.6 regarding the electrolysis of copper chloride. It includes two diagrams: Figure 1 shows a beaker with a power supply connected to two electrodes in a copper chloride solution, and Figure 2 shows the same setup with bubbles at the positive electrode and a deposit at the negative electrode. The questions ask for the state of the substance, reasons for ion movement, the source of ions, identification of metal-producing ions, descriptions of observations at electrodes, and a calculation of mass.
Question text

02 This question is about electrolysis.

02.1 Complete the sentence.

Choose the answer from the box.

[1 mark]

gaseous molten solid

Copper chloride can conduct electricity when in solution or

when .

Figure 1 shows the apparatus used for the electrolysis of copper chloride solution.

Figure 1

There are four ions in copper chloride solution:

• Cu2+

–

• Cl

• H+

– 7

• OH

02 2 – –

. Why do Cl ions and OH ions move to the positive electrode?

[1 mark]

02 3 + –

. Where do the H and OH ions come from in the electrolysis of

copper chloride solution?

[1 mark]

Tick ( ) one box.

Air

Copper chloride

Water

02.4 Which ion produces a metal?

[1 mark]

Tick ( ) one box.

Cu2+

–

Cl

H+

–

OH 8

02.5 Figure 2 shows the apparatus during the electrolysis of copper chloride solution.

Figure 2

Describe what is seen at each electrode during the electrolysis of

copper chloride solution.

[2 marks]

Positive electrode

Negative electrode

02.6 500 cm3 of copper chloride solution contains 6.50 g of copper chloride.

Calculate the mass of copper chloride in 40.0 cm3 of this copper chloride solution.

[2 marks]

Mass = g

Mark scheme

Show the mark scheme The mark scheme is a table listing the question numbers from 02.1 to 02.6, the correct answers, extra information for marking, the marks awarded for each part, and the assessment objective/specification reference. It confirms the correct answers: 'molten', 'opposite charges attract', 'water', 'Cu2+', 'bubbles/effervescence' and 'solid/pink-brown deposit', and the calculation steps for the final mass.

AO /

Question Answers Extra information Mark

Spec. Ref.

02.1 molten 1 AO2

5.2.3.2

5.4.3.1

5.4.3.2

02.2 opposite (charges) attract 1 AO1

or 5.4.3.1

(the ions) are negative(ly 5.4.3.4

charged) RPA9

02.3 water 1 AO1

5.4.3.4

02.4 Cu2+ 1 AO2

5.4.3.1

5.4.3.4

RPA9

02.5 (positive electrode) AO3

bubbles / effervescence / fizzing allow gas (is produced) 1 5.4.3.1

5.4.3.4

(negative electrode) RPA9

(pink / orange / red / brown) allow copper (plating) 1

solid allow metal for solid

02.6 40.0 AO2

× 6.50 1 5.1.2.6

5.3.2.5

= 0.52 (g) 1

Total 8

How to answer it

Electrolysis of Aqueous Copper Chloride

What this question tests

This question assesses your understanding of electrolysis (Required Practical 9). You need to know why ionic compounds conduct electricity, how ions move towards electrodes based on charge, and how to describe observations. It also tests basic quantitative chemistry using ratios of mass and volume.

Question 02.1

Ionic Conductivity

Correct Answer

molten

Key Knowledge

Ionic compounds (like copper chloride) only conduct electricity when liquid (molten) or dissolved (aqueous). This is because the ions are free to move and carry charge.

Common Error

Students often choose "solid". In a solid, ions are locked in a fixed lattice and cannot move, so they cannot conduct electricity.

Questions 02.2 & 02.3

Ion Movement and Origins

02.2: Why do ions move to the positive electrode?

Correct Answer

  • Opposite charges attract
  • OR The ions are negatively charged

Exam Technique

Always use the word attract when talking about charges. Remember: PANIC (Positive Anode, Negative Is Cathode). Negative ions (anions) move to the positive electrode.

02.3: Where do H⁺ and OH⁻ ions come from?

Correct Answer

Water

Key Knowledge

In aqueous electrolysis, the water molecules (H₂O) partially ionise into Hydrogen ions (H⁺) and Hydroxide ions (OH⁻).

Questions 02.4 & 02.5

Identifying Products and Observations

02.4: Which ion produces a metal?

Correct Answer

Cu²⁺

02.5: Describe what is seen at each electrode

Correct Answer

Positive electrode: Bubbles / fizzing / effervescence

Negative electrode: Pink / orange / brown solid

Exam Technique

When a question asks what is seen, do not just name the chemical. "Chlorine" is a chemical name; "bubbles" is what you see. "Copper" is a name; "orange solid" is the observation.

Diagram Description

If you were asked to draw this: The positive electrode (anode) should show small circles representing gas bubbles. The negative electrode (cathode) should have a thick, shaded layer on the surface representing the metal plating.

Question 02.6

Calculation: Mass in Volume

Step-by-Step Calculation

The solution has 6.50 g in 500 cm³. We need to find the mass in 40.0 cm³.

  1. Find the ratio: Divide the new volume by the original volume.
    40.0 / 500 = 0.08
  2. Apply to mass: Multiply the total mass by this ratio.
    0.08 × 6.50 g = 0.52 g

Final Answer: 0.52 g

Mark Breakdown

  • 1 Mark: Showing the correct substitution/method (e.g., 40/500 × 6.5).
  • 1 Mark: Correct final answer of 0.52.

Calculation Traps

Ensure you don't flip the fraction! If you did 500 / 40, you would get a mass much larger than the original, which is impossible. Always check if your answer "looks" sensible.

Topics

Chemistry · C4: Chemical Changes

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