Free Electrolysis questions for IGCSE Chemistry (0620), part of Electrochemistry. Each question has the answer and the marking points an examiner would look for.
Generate a full Electrolysis worksheet →All Electrochemistry questionsWhich ionic half-equation shows the reaction at the cathode during the electrolysis of aqueous copper(II) sulfate?
Answer: A
What are the products at the electrodes when molten lead(II) bromide is electrolysed?
| cathode | anode | |
|---|---|---|
| A | lead | oxygen |
| B | lead | bromine |
| C | bromine | lead |
| D | chlorine | bromine |
Answer: B
Concentrated aqueous sodium chloride is electrolysed using inert electrodes.
Name the products at the anode and at the cathode.
Write the ionic half-equation for the reaction at the cathode.
Name the solution left at the end.
| Part | Answer and marking points | Marks |
|---|---|---|
| (a) | chlorine; hydrogen anode: chlorine B1 cathode: hydrogen B1 | 2 |
| (b) | 2H⁺ + 2e⁻ → H₂ 2H⁺ + 2e⁻ → H₂ (or 2H₂O + 2e⁻ → H₂ + 2OH⁻) B2 | 2 |
| (c) | sodium hydroxide sodium hydroxide (solution) B1 | 1 |
Molten lead(II) bromide is electrolysed.
Explain why the lead(II) bromide must be molten.
State what is seen at each electrode.
State the type of particle that carries the current through the wires.
| Part | Answer and marking points | Marks |
|---|---|---|
| (a) | ions free to move so the ions are free to move B1 | 1 |
| (b) | silver/grey lead at cathode; brown bromine at anode cathode: grey/silver liquid lead B1 anode: brown (red-brown) bromine vapour B1 | 2 |
| (c) | electrons electrons B1 | 1 |
Electroplating is used to coat objects with a thin layer of metal.
A key is to be silver-plated. State what the anode, cathode and electrolyte should be.
Give two reasons for electroplating.
| Part | Answer and marking points | Marks |
|---|---|---|
| (a) | silver anode; key cathode; silver nitrate anode: silver B1 cathode: the key B1 electrolyte: a solution containing silver ions (silver nitrate) B1 | 3 |
| (b) | appearance; prevent corrosion improve appearance B1 prevent corrosion B1 | 2 |
Fig. 6.1 shows the apparatus for the electrolysis of concentrated aqueous sodium chloride using inert electrodes.
Name the products formed at the anode, at the cathode, and left in solution.
Describe a test for the gas produced at the anode and give the result.
The solution contains Na⁺, H⁺, Cl⁻ and OH⁻ ions.
Write the ionic half-equation for the formation of hydrogen at the cathode.
Explain why hydrogen, not sodium, is produced at the cathode.
Explain why the solution becomes alkaline during the electrolysis.
The electrolysis is repeated using dilute aqueous sodium chloride. Name the gas now produced at the anode and explain why it is different from the gas produced from concentrated solution.
| Part | Answer and marking points | Marks |
|---|---|---|
| (a) | anode chlorine; cathode hydrogen; solution sodium hydroxide anode: chlorine B1 cathode: hydrogen B1 solution: sodium hydroxide B1 | 3 |
| (b) | damp litmus paper is bleached damp (blue) litmus paper B1 bleached / turns white B1 | 2 |
| (c)(i) | 2H⁺ + 2e⁻ → H₂ 2H⁺ + 2e⁻ B1 → H₂ B1 | 2 |
| (ii) | hydrogen is less reactive than sodium, so H⁺ is discharged hydrogen is less reactive than sodium B1 so H⁺ ions are discharged / gain electrons in preference to Na⁺ B1 | 2 |
| (iii) | H⁺ and Cl⁻ are removed, so OH⁻ and Na⁺ remain H⁺ ions and Cl⁻ ions are removed B1 leaving Na⁺ and OH⁻ ions / sodium hydroxide in solution B1 | 2 |
| (d) | oxygen; Cl⁻ concentration too low, OH⁻ discharged oxygen B1 the concentration of chloride ions is low so hydroxide ions are discharged instead B1 | 2 |
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Meet Riyaz →Original Cambridge-style practice questions written for mentorriyaz.in. These are not Cambridge past paper questions, and this site is not affiliated with or endorsed by Cambridge University Press & Assessment. Updated 2026-11-04. Paper generator · mentorriyaz.in