A hydrogen fuel cell has an acidic electrolyte. Which half equation for the reaction at the negative electrode of this fuel cell is balanced correctly?
2H2→4H++4e−2\text{H}_2 \rightarrow 4\text{H}^+ + 4\text{e}^-2H2→4H++4e−
2H2→4H++2e−2\text{H}_2 \rightarrow 4\text{H}^+ + 2\text{e}^-2H2→4H++2e−
2H2→2H++4e−2\text{H}_2 \rightarrow 2\text{H}^+ + 4\text{e}^-2H2→2H++4e−
2H2→2H++2e−2\text{H}_2 \rightarrow 2\text{H}^+ + 2\text{e}^-2H2→2H++2e−
40 exam-style questions on AQA GCSE Chemistry 5.2 Chemical cells and fuel cells, covering 5.2.1 Cells and batteries, 5.2.2a Fuel cells, and 5.2.2b Half equations for hydrogen fuel cells. Each one has a worked solution and a mark scheme showing where the marks go.