Pearson Edexcel International GCSE (9–1) · CHEMISTRY · Section
Electrolysis and redox
19 practice questions
Practice questions
11–19 of 19
Question 11
3 marks · Normal
Answer and see the solution →The electrolysis of molten potassium chloride (KCl) produces potassium metal and chlorine gas.
(a)[1 mark]Write the half-equation for the reaction at the cathode.
(b)[1 mark]State whether the reaction at the cathode is oxidation or reduction.
(c)[1 mark]Explain your answer to part (b) in terms of electron transfer.
Question 12
3 marks · Normal
Answer and see the solution →A student wants to remember whether oxidation or reduction involves losing or gaining electrons.
(a)[1 mark]State the mnemonic used to remember this.
(b)[1 mark]What does each letter in the mnemonic stand for?
(c)[1 mark]Explain, using the mnemonic, what happens to an ion that gains electrons.
Question 13
4 marks · Normal
Answer and see the solution →Table 1: Electrode Reactions Ion Half-equation Cl^- 2Cl^- \rightarrow Cl_2 + 2e^- Ag^+ Ag^+ + e^- \rightarrow Ag Fe^{3+} Fe^{3+} + 3e^- \rightarrow Fe O^{2-} 2O^{2-} \rightarrow O_2 + 4e^- Study Table 1. For each reaction below, state whether the ion is oxidised or reduced and explain why using electron transfer.
(a)[1 mark]Cl^- \rightarrow Cl_2 + 2e^-
(b)[1 mark]Ag^+ + e^- \rightarrow Ag
(c)[1 mark]Fe^{3+} + 3e^- \rightarrow Fe
(d)[1 mark]O^{2-} \rightarrow O_2 + 4e^-
Question 14
1 mark · Normal
Answer and check →In the electrolysis of molten zinc bromide, what does it mean to 'discharge' a zinc ion (Zn^{2+}) at the cathode?
- A.Zinc ions lose electrons to form zinc atoms.
- B.Zinc ions gain electrons to form zinc atoms.
- C.Zinc atoms lose electrons to form zinc ions.
- D.Zinc ions are removed from the solution by evaporation.
Question 15
2 marks · Normal
Answer and see the solution →For the electrolysis of molten calcium bromide (CaBr_2):
(a)[1 mark]Which electrode (anode or cathode) is the site of oxidation?
(b)[1 mark]Which electrode reaction involves reduction?
Question 16
4 marks · Normal
Answer and see the solution →You are asked to explain how the OILRIG mnemonic helps when deciding whether a reaction is oxidation or reduction.
(a)[2 marks]Write what each letter in OILRIG stands for.
(b)[1 mark]Use the mnemonic to decide whether the following process is oxidation or reduction: Fe^{2+} gains 2 electrons to form Fe.
(c)[1 mark]State how the mnemonic helps you to answer part (b).
Question 17
2 marks · Hard
Answer and see the solution →Define oxidation and reduction in terms of electron transfer. Give your answers using complete sentences.
Question 18
5 marks · Hard
Answer and see the solution →The apparatus below is used to electrolyse molten tin(II) chloride (SnCl₂). Tin(II) ions (Sn²⁺) and chloride ions (Cl⁻) move towards the electrodes and react.
Electrolysis setup for molten tin(II) chloride (a) State what is meant by 'discharging' a tin(II) ion during the electrolysis of molten tin(II) chloride.
(a)[2 marks]State what is meant by 'discharging' a tin(II) ion during the electrolysis of molten tin(II) chloride.
(b)[2 marks]Explain, in terms of electron transfer, what happens to a tin(II) ion at the cathode in this process.
(c)[1 mark]Write a half-equation for the reaction involving tin(II) ions at the cathode.
Question 19
2 marks · Hard
Answer and see the solution →The electrolysis of molten iron(III) chloride (FeCl₃) involves reactions at both electrodes.
State which electrode reaction involves oxidation, and which involves reduction. Explain your answer with reference to loss or gain of electrons.