Redox and electrochemistry — Question 24

24a)

Similarity: Both the Pt and Cu half-cells have a positive standard reduction potential compared to SHE. Difference: Pt half-cell is more positive than Cu half-cell. Significance: Cu electrode is oxidised (loses electrons) and the Fe³⁺(aq) is reduced.

• Similarities: identifies that both half-cells have positive standard reduction potential [1 mark]

• Differences: identifies that Pt half-cell is more positive than Cu half-cell [1 mark]

• Significance: explains that Cu electrode is oxidised and Fe³⁺ is reduced [1 mark]

24b)

Balance redox equation: 3

2 2

+

+ +

2Fe Cu Cu 2Fe

+ $\rightarrow$ +

• provides correct balanced redox equation [1 mark]

24c)

$\mathrm{C}\mathrm{e}\mathrm{l}\mathrm{l}\,\mathrm{p}\mathrm{o}\mathrm{t}\mathrm{e}\mathrm{n}\mathrm{t}\mathrm{i}\mathrm{a}\mathrm{l}\,=\,0.77\,+\,(-0.34)\,=\,+0.43\,\mathrm{V}\,$

• determines cell potential is +0.43 [1 mark]

24d)

Fe³⁺ is the oxidising agent, because ON decreases from +3 to +2.

• identifies Fe³⁺ as the oxidising agent [1 mark]

• indicates oxidation number decreases [1 mark]