Electrolysis: Edexcel International GCSE Chemistry questions

Every Edexcel International GCSE Chemistry exam question on Electrolysis (specification points 1.55–1.60), 2019–2025, with its mark scheme and examiner’s report.

All 80 questions on Electrolysis, as a list

June 2025, Paper 2, Q3(d) (5 marks): The table lists some substances and shows which substance conducts electricity. Substance Conducts electricity? water no solid magnesium chloride no aqueous mag
June 2025, Paper 2, Q3(e)(i) (1 mark): Give the half‑equation for the reaction at the positive electrode. (1)
June 2025, Paper 2, Q3(e)(ii) (1 mark): Give a reason why this reaction is classified as oxidation. (1)
June 2024, Paper 2, Q6(c)(i) (3 marks): Explain why lead(II) bromide needs to be molten rather than solid for electrolysis to occur. (3)
June 2024, Paper 2, Q6(c)(ii) (2 marks): The electrolyte is at a temperature of 400 °C. Explain a suitable material for the electrodes. (2)
June 2024, Paper 2, Q6(c)(iii) (1 mark): Give the half‑equation that occurs at the negative electrode. (1)
June 2024, Paper 2, Q6(d)(i) (1 mark): State what is observed at the positive electrode. (1)
June 2024, Paper 2, Q6(d)(ii) (1 mark): State why the half‑equation represents an oxidation reaction. (1)
June 2024 (R), Paper 2, Q6(a)(i) (1 mark): Name a suitable material for the inert electrodes. (1)
June 2024 (R), Paper 2, Q6(a)(iv) (1 mark): Give an ionic half-equation for the formation of hydrogen at the negative electrode. (1)
June 2024 (R), Paper 2, Q6(b)(i) (1 mark): Give a reason why sodium chloride solution conducts electricity. (1)
June 2024 (R), Paper 2, Q6(b)(ii) (1 mark): The positive ions in the solution are H+ and Na+. Give a reason why hydrogen forms at the negative electrode rather than sodium. (1)
June 2024 (R), Paper 2, Q6(b)(iii) (2 marks): A sample of the solution is taken from near the negative electrode. The sample is tested with universal indicator. Explain the final colour of the universal ind
November 2023, Paper 2, Q7(a) (2 marks): Sodium chloride is an ionic compound. Explain why sodium chloride conducts electricity when it is molten or in solution, but not when it is solid. (2)
November 2023, Paper 2, Q7(b)(i) (1 mark): If the solution is dilute, a significant amount of oxygen collects at P. Complete the ionic half-equation for this reaction. (1) H2O → H+ + O2 + e–
November 2023, Paper 2, Q7(b)(ii) (1 mark): If the solution is concentrated, chlorine is the main product that collects at P. This is the ionic half-equation for the reaction. 2Cl– → Cl2 + 2e– State why t
November 2023, Paper 2, Q7(c)(ii) (3 marks): Explain how hydrogen gas forms at the negative electrode. (3)
June 2023, Paper 2, Q5(b) (3 marks): Describe how copper metal forms at the negative electrode. (3)
June 2023, Paper 2, Q5(c) (1 mark): State the appearance of the copper that forms on the negative electrode. (1)
June 2023, Paper 2, Q5(d)(ii) (2 marks): Complete the half-equation for the formation of oxygen at the positive electrode. (2) 2H2O → + +
June 2023, Paper 2, Q5(d)(iii) (1 mark): State why the formation of oxygen at the positive electrode is an oxidation reaction. (1)
June 2023 (R), Paper 2, Q5(d) (1 mark): The diagram shows the electrolysis of molten lead(II) bromide, PbBr2 + – A B crucible molten lead(II) bromide This is the ionic half‑equation for the formation
January 2023, Paper 2, Q5(b)(i) (2 marks): Explain why molten sodium chloride conducts electricity. (2)
January 2023, Paper 2, Q5(b)(ii) (2 marks): Explain how sodium metal forms at the negative electrode. (2)
January 2023, Paper 2, Q5(b)(iii) (1 mark): Write an ionic half-equation for the formation of chlorine gas at the positive electrode. (1)
January 2023, Paper 2, Q5(b)(iv) (1 mark): Give a reason why sodium metal does not form in the electrolysis of an aqueous solution of sodium chloride. (1)
January 2023 (R), Paper 2, Q6(b)(i) (2 marks): Explain why the molten electrolyte conducts electricity. (2)
January 2023 (R), Paper 2, Q6(b)(ii) (1 mark): What is the formula of the cation in the electrolyte? (1) A H+ B Cl– C Na+ D OH–
January 2023 (R), Paper 2, Q6(b)(iv) (2 marks): Give ionic half-equations for the reactions at the anode and cathode. (2) anode . cathode
June 2022, Paper 2, Q4(c)(ii) (4 marks): Explain the different ways that magnesium and magnesium chloride conduct electricity. (4) magnesium magnesium chloride
June 2022, Paper 2, Q4(d)(i) (1 mark): State why this is a reduction reaction. (1)
June 2022, Paper 2, Q4(d)(ii) (1 mark): Write an ionic half‑equation for the formation of chlorine at the positive electrode. (1)
June 2022 (R), Paper 1, Q10(a)(ii) (2 marks): Plot the student’s results. (2)
June 2022 (R), Paper 1, Q10(a)(iii) (1 mark): Ignoring the anomalous result, draw two lines of best fit, making sure that the two lines cross. (1) 10.0 8.0 6.0 Electrical conductivity in arbitrary units 4.0
June 2022 (R), Paper 1, Q10(a)(iv) (1 mark): Give the trend shown on the graph for the first 50 cm3 of acid added. (1)
June 2022 (R), Paper 1, Q10(a)(v) (1 mark): Suggest a mistake the student could have made to cause the anomalous result. (1)
June 2022 (R), Paper 2, Q4(b)(ii) (1 mark): State what would be seen at the positive electrode. (1)
June 2022 (R), Paper 2, Q4(b)(iv) (2 marks): Give an ionic half‑equation for the formation of oxygen at the positive electrode. . (2)
June 2022 (R), Paper 2, Q4(b)(v) (1 mark): Suggest why the copper(II) sulfate solution contains some OH– ions. (1)
January 2022, Paper 2, Q6(a)(i) (1 mark): Plot the student’s results. (1)
January 2022, Paper 2, Q6(a)(ii) (1 mark): Draw a curve of best fit. (1) 0.50 0.40 0.30 Increase in mass in grams 0.20 0.10 0 0 1 2 3 4 5 6 7 8 Time in minutes
January 2022, Paper 2, Q6(a)(iii) (2 marks): Explain the shape of the graph. (2)
January 2022, Paper 2, Q6(b)(i) (2 marks): The student repeats the electrolysis using different apparatus. positive electrode negative electrode Describe how the student should collect a sample of pure o
January 2022, Paper 2, Q6(b)(ii) (2 marks): Give an ionic half-equation for the formation of oxygen. (2)
January 2022 (R), Paper 2, Q6(b) (2 marks): The teacher then sets up a circuit in a fume cupboard using the pure, dry sample of lead(II) bromide. + − positive electrode negative electrode crucible lead(II
January 2022 (R), Paper 2, Q6(c)(i) (1 mark): State what observation would be made at the positive electrode. (1)
January 2022 (R), Paper 2, Q6(c)(ii) (4 marks): Explain how bromide ions in the molten lead(II) bromide become bromine molecules at the positive electrode. (4)
January 2022 (R), Paper 2, Q6(d) (2 marks): Write an ionic half-equation for the reaction that occurs at the negative electrode. Include state symbols in your equation. (2)
November 2021, Paper 2, Q4(d) (2 marks): Explain why ionic compounds conduct electricity when molten or in aqueous solution, but not when in the solid state. (2)
November 2021, Paper 2, Q4(e) (4 marks): The diagram shows the apparatus a teacher uses to demonstrate the electrolysis of a concentrated aqueous solution of sodium chloride. gas X gas Y sodium chlorid
June 2021, Paper 2, Q6(b)(i) (1 mark): State why this reaction is an oxidation reaction. (1)
June 2021, Paper 2, Q6(b)(ii) (1 mark): Give the ionic half-equation for the formation of hydrogen at the negative electrode. (1)
June 2021, Paper 2, Q6(b)(iii) (1 mark): State why it is safer to do this electrolysis in a fume cupboard. (1)
June 2021, Paper 2, Q6(b)(iv) (1 mark): Suggest why the volume of chlorine collected during this electrolysis is less than the volume of hydrogen collected. (1)
June 2021, Paper 2, Q6(c)(i) (2 marks): Explain why sodium chloride needs to be molten rather than solid for electrolysis to occur. (2)
January 2021 (R), Paper 2, Q3(a) (4 marks): Explain why metals conduct electricity but covalent compounds do not conduct electricity. (4)
January 2021 (R), Paper 2, Q3(b) (1 mark): Hydrogen chloride, HCl, is a covalent substance. When hydrogen chloride is added to water, a solution of dilute hydrochloric acid is formed. This solution does
January 2021 (R), Paper 2, Q3(c)(i) (1 mark): Plot the results for syringe Y. (1)
January 2021 (R), Paper 2, Q3(c)(ii) (1 mark): Draw a circle around the anomalous result. (1)
January 2021 (R), Paper 2, Q3(c)(iii) (1 mark): Draw a line of best fit. (1) 80 70 60 50 40 30 20 10 0 0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 Current in amp
January 2021 (R), Paper 2, Q3(c)(iv) (2 marks): Explain a possible cause of the anomalous result, other than misreading the apparatus. (2)
January 2021 (R), Paper 2, Q3(c)(v) (1 mark): Deduce the relationship between current and volume of gas collected in syringe Y. (1)
January 2021 (R), Paper 2, Q3(d)(i) (1 mark): Suggest how these ionic half‑equations show that the volume of chlorine collected in syringe X should be the same as the volume of hydrogen collected in syringe
January 2021 (R), Paper 2, Q3(d)(ii) (1 mark): Suggest why the volume of chlorine collected in syringe X is always less than the volume of hydrogen collected in syringe Y. (1)
November 2020, Paper 2, Q6(a)(i) (1 mark): Suggest why the student does not use zinc electrodes in her experiment. (1)
November 2020, Paper 2, Q6(a)(ii) (1 mark): State what is observed at both the anode and the cathode during the electrolysis. (1)
January 2020, Paper 2, Q3(b)(i) (2 marks): State what would be observed at each electrode. (2) negative electrode positive electrode
January 2020, Paper 2, Q3(b)(ii) (1 mark): The ionic half‑equation for the reaction at the negative electrode is Cu2+ + 2e– → Cu State why this is a reduction reaction. (1)
January 2020, Paper 2, Q3(b)(iii) (2 marks): Explain why the copper(II) sulfate solution becomes paler blue during the electrolysis. (2)
January 2020 (R), Paper 1, Q8(c)(i) (3 marks): Plot the results on the grid and draw two straight lines of best fit. Ignore the anomalous result. (3) 40 30 Conductivity of solution 20 in arbitrary units 10 0
January 2020 (R), Paper 1, Q8(c)(ii) (1 mark): State the trend shown on the graph for the first six spatulas of calcium chloride. (1)
January 2020 (R), Paper 1, Q8(c)(iii) (1 mark): Suggest an error the student could have made to cause the anomalous result. (1)
January 2020 (R), Paper 1, Q8(d) (2 marks): Describe another way to make solid calcium chloride conduct electricity. (2)
January 2020 (R), Paper 2, Q4(b)(i) (1 mark): State why solid lead(II) bromide does not conduct electricity. (1)
January 2020 (R), Paper 2, Q4(b)(ii) (1 mark): Bromine is formed by the oxidation of bromide ions at the positive electrode. Complete the ionic half-equation for the oxidation of bromide ions. (1) 2Br– o +
January 2020 (R), Paper 2, Q4(b)(iii) (2 marks): Explain why lead metal forms at the negative electrode. (2)
June 2019 (R), Paper 2, Q4(d) (5 marks): A student sets up a circuit to test the electrical conductivity of water, solid sodium chloride and aqueous sodium chloride. The table shows the student’s resul
June 2019 (R), Paper 2, Q4(e)(i) (1 mark): Give an ionic half‑equation for the formation of chlorine at the positive electrode. (1)
June 2019 (R), Paper 2, Q4(e)(ii) (1 mark): State why this ionic half‑equation represents an oxidation reaction. (1)
June 2019 (R), Paper 2, Q4(e)(iii) (1 mark): Which substance is formed at the negative electrode (cathode)? (1) A hydrogen B oxygen C sodium D water

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