Electrolysis and redox
4 marks · Normal| 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.
Cl^- \rightarrow Cl_2 + 2e^-
Ag^+ + e^- \rightarrow Ag
Fe^{3+} + 3e^- \rightarrow Fe
O^{2-} \rightarrow O_2 + 4e^-
Work this out on paper, then compare with the answer and worked solution below. With a free account you can submit written answers for marking.
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(a) Oxidised; chloride ions lose electrons.
(b) Reduced; silver ions gain electrons.
(c) Reduced; iron(III) ions gain electrons.
(d) Oxidised; oxide ions lose electrons.
Common mistakes: Stating oxidation/reduction without reference to electrons.
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Marking points
B1 (a) · 1 mark · States Cl^- is oxidised/loses electrons.
B1 (b) · 1 mark · States Ag^+ is reduced/gains electrons.
B1 (c) · 1 mark · States Fe^{3+} is reduced/gains electrons.
B1 (d) · 1 mark · States O^{2-} is oxidised/loses electrons.
Worked solution
a. Oxidised; chloride ions lose electrons.
b. Reduced; silver ions gain electrons.
c. Reduced; iron(III) ions gain electrons.
d. Oxidised; oxide ions lose electrons.