2023 H2 Chem P1 Q29 — Electrochemical cell Solution

The answer is B (1 only).
• Statement 1, correct. The SHE has \(E^\ominus = 0.00\) V. When it is connected to a half-cell with a negative \(E^\ominus\) (e.g. \(\text{Zn}^{2+}/\text{Zn}\), \(-0.76\) V), that half-cell is oxidised and the SHE is the cathode, where \(2\text{H}^+ + 2\text{e}^- \rightarrow \text{H}_2\), so hydrogen gas is made.
• Statement 2, incorrect. By definition, \(E^\ominus(\text{H}^+/\text{H}_2) = 0.00\) V, not 1.00 V.
• Statement 3, incorrect. The SHE needs \([\text{H}^+] = 1.00\text{ mol dm}^{-3}\). Sulfuric acid is diprotic, so 1.00 mol dm\(^{-3}\) \(\text{H}_2\text{SO}_4\) gives more than 1.00 mol dm\(^{-3}\) of \(\text{H}^+\) (2.00 mol dm\(^{-3}\) if fully ionised), which is not standard.
• A is wrong: it includes statement 3, but 1.00 mol dm\(^{-3}\) \(\text{H}_2\text{SO}_4\) does not give 1.00 mol dm\(^{-3}\) \(\text{H}^+\).
• C is wrong: statements 2 and 3 are both incorrect.
• D is wrong: statement 2 is incorrect (the SHE is 0.00 V), and it leaves out statement 1.