2023 H2 Chem P1 Q28 — Electrochemical cell Solution

The answer is A (1, 2 and 3).
• Statement 1, correct. The overall reaction is \(2\text{H}_2 + \text{O}_2 \rightarrow 2\text{H}_2\text{O}\); the only product is water, which is not environmentally harmful.
• Statement 2, correct. The fuel cell converts chemical energy directly into electrical energy, without first burning the fuel to make heat, so little energy is lost and the efficiency is high.
• Statement 3, correct. At the anode, hydrogen is oxidised: \(\text{H}_2 \rightarrow 2\text{H}^+ + 2\text{e}^-\).
• B is wrong: it leaves out statement 3, but \(\text{H}_2\) does release electrons and form \(\text{H}^+\) at the anode.
• C is wrong: it leaves out statement 1, but water is the only product.
• D is wrong: it leaves out statements 1 and 2, which are both correct.