O Level Chemistry 5070 · Topic 4

Electrochemistry: past paper questions

170 real questionsasked in 10 of the last 10 exam series2019–2025usually: Describe, Complete, State, Explain, Predict

Real questions on electrochemistry

The newest 20 of 111 written questions, plus 59 multiple-choice. Open one to see it on the real paper.

5070/21 · October/November 2025 · Q9e[4]
Aqueous copper( II ) sulfate is electrolysed separately with carbon electrodes and with copper electrodes. Complete Table 9.1. Table 9.1 carbon electrodes copper electrodes observations at anode observations at cathode electrolysis of aqueous copper( II ) sulfate
See it on the paper →
5070/21 · October/November 2025 · Q9f[1]
Explain why aqueous copper( II ) sulfate conducts electricity but solid copper( II ) sulfate does not conduct electricity. (f)
See it on the paper →
5070/22 · October/November 2025 · Q9d[4]
Dilute and concentrated aqueous zinc chloride are electrolysed separately using carbon electrodes. Complete Table 9.1. Table 9.1 dilute aqueous zinc chloride concentrated aqueous zinc chloride product at anode product at cathode
See it on the paper →
5070/21 · May/June 2025 · Q2b[2]
Predict the products of the electrolysis of concentrated aqueous copper( II ) bromide with graphite electrodes. product at anode
See it on the paper →
5070/21 · May/June 2025 · Q2c[2]
Dilute sulfuric acid is electrolysed using graphite electrodes to form oxygen and hydrogen. Construct the ionic half‑equation for the reaction at each electrode. reaction at anode
See it on the paper →
5070/21 · May/June 2025 · Q2d(i)[1]
Name the only chemical product formed in a fuel cell.
See it on the paper →
5070/21 · May/June 2025 · Q2d(ii)[1]
Describe one disadvantage of using hydrogen–oxygen fuel cells in vehicles compared to gasoline or petrol engines.
See it on the paper →
5070/21 · May/June 2025 · Q3a[1]
State one condition for this reaction.
See it on the paper →
5070/22 · May/June 2025 · Q2b[2]
Predict the products of the electrolysis of dilute aqueous magnesium chloride with graphite electrodes. product at anode
See it on the paper →
5070/22 · May/June 2025 · Q2c[2]
Molten aluminium oxide is electrolysed using graphite electrodes to form oxygen and aluminium. Construct the ionic half-equation for the reaction at each electrode. reaction at anode
See it on the paper →
5070/22 · May/June 2025 · Q2d[2]
A metal object is electroplated with copper. The metal object is the cathode during this electrolysis. State the name of the substance used for the anode and for the electrolyte. anode
See it on the paper →
5070/21 · October/November 2024 · Q3a[1]
Label the cathode on Fig. 3.1.
See it on the paper →
5070/21 · October/November 2024 · Q3b[1]
Explain why concentrated aqueous sodium chloride conducts electricity.
See it on the paper →
5070/21 · October/November 2024 · Q3c(i)[1]
Name the product formed at the cathode.
See it on the paper →
5070/21 · October/November 2024 · Q3c(ii)[1]
Chlorine is formed at the anode. Construct the ionic half-equation for the reaction at the anode.
See it on the paper →
5070/21 · October/November 2024 · Q3d[1]
Graphite is suitable as an electrode because it conducts electricity. State one other property of graphite that makes it suitable for use as an electrode.
See it on the paper →
5070/21 · October/November 2024 · Q3e[1]
State the product formed at the cathode when molten sodium chloride is electrolysed.
See it on the paper →
5070/22 · October/November 2024 · Q3a[2]
Define the term electrolysis.
See it on the paper →
5070/22 · October/November 2024 · Q3b[1]
Label the anode on Fig. 3.1.
See it on the paper →
5070/22 · October/November 2024 · Q3c(i)[1]
Name the product at the cathode.
See it on the paper →

What examiners said

Some candidates gave ionic half-equations for the electrode reactions, most of which were incorrect. Other candidates gave formulae, more often than not these were not correct. For example, giving ions or monoatomic iodine. Iodine as the product at the anode was the most common correct product and magnesium as the product at the cathode was the most common incorrect answer.
— Examiner report, October/November 2023, 5070/22 Q4(a) (Cambridge)

Candidates were often unable to write the correct ionic half-equations. Typical errors included the incorrect products, incorrect formulae such as Mg2 and electrons on the wrong side of the equation. A small but significant proportion of the candidates did not attempt the question.
— Examiner report, October/November 2023, 5070/22 Q4(b) (Cambridge)

Candidates often stated that water was formed but rarely mentioned that water was the only product. A common misconception was that no greenhouse gases were emitted even though water is a greenhouse gas. Some candidates appreciated that a hydrogen-oxygen fuel cell was more efficient that a petrol engine. Other candidates appreciated that hydrogen is a renewable fuel (if made from water). Candidate...
— Examiner report, October/November 2023, 5070/22 Q6(c) (Cambridge)

Practise this topic

Answer these questions online and get each one marked against the official mark scheme, with what you missed and how to fix it.

Practise electrochemistry

In the syllabus

4.1 Electrolysis

Define electrolysis as the decomposition of an ionic compound, when molten or in aqueous solution, by the passage of an electric current
Identify in simple electrolytic cells: (a) the anode as the positive electrode (b) the cathode as the negative electrode (c) the electrolyte as the molten or aqueous substance that undergoes electrolysis
Describe the transfer of charge during electrolysis to include: (a) the movement of electrons in the external circuit (b) the loss or gain of electrons at the electrodes (c) the movement of ions in the electrolyte
Identify the products formed at the electrodes and describe the observations made during the electrolysis of: (a) molten lead(II) bromide (b) concentrated aqueous sodium chloride (c) dilute sulfuric acid using inert electrodes made of platinum or carbon / graphite
Identify the products formed at the electrodes and describe the observations made during the electrolysis of aqueous copper(II) sulfate using inert carbon / graphite electrodes and when using copper electrodes
State that metals or hydrogen are formed at the cathode and that non-metals (other than hydrogen) are formed at the anode
Predict the identity of the products at each electrode for the electrolysis of a binary compound in the molten state
Predict the identity of the products at each electrode for the electrolysis of a halide compound in dilute or concentrated aqueous solution
Construct ionic half-equations for reactions at the anode (to show oxidation) and at the cathode (to show reduction)
State that metal objects are electroplated to improve their appearance and resistance to corrosion
Describe how metals are electroplated

4.2 Hydrogen–oxygen fuel cells

State that a hydrogen–oxygen fuel cell uses hydrogen and oxygen to produce electricity with water as the only chemical product
Describe the advantages and disadvantages of using hydrogen–oxygen fuel cells in comparison with gasoline / petrol engines in vehicles

Past papers, syllabus and examiner reports © UCLES (Cambridge University Press & Assessment). Questions are matched to topics from the official syllabus. AssessPro is independent and not endorsed by Cambridge.