Question detail
For Fuel cells, which answer best supports this AQA GCSE Chemistry Unit 4.5 objective: (chemistry only) (HT only) Write the half equation for the oxygen electrode reaction in a hydrogen fuel cell when formulae and charges are supplied?
Try the question, check the answer, then read the explanation to understand the curriculum point.
At a glance
MCQ
Type
practice
Style
Topic
Chemical cells and fuel cells (chemistry only)
Question
- A. chemistry only: correct Unit 4.5 answer for Fuel cells
- B. Incorrect: confuses chemistry only with a nearby Energy changes idea
- C. Incorrect: gives a general chemistry statement without linking to Fuel cells
- D. Incorrect: reverses the energy-change relationship in Chemical cells and fuel cells (chemistry only)
Answer
The correct option is chemistry only: correct Unit 4.5 answer for Fuel cells.
Explanation
The correct option is chemistry only: correct Unit 4.5 answer for Fuel cells. It directly supports the approved learning objective to (chemistry only) (HT only) Write the half equation for the oxygen electrode reaction in a hydrogen fuel cell when formulae and charges are supplied. This keeps the answer anchored to Fuel cells within Chemical cells and fuel cells (chemistry only), and avoids mixing energy transfer, reaction profiles, activation energy, chemical cells, fuel cells, exothermic reactions and endothermic reactions unless the objective names them.
Common mistake
Oxygen half‑reaction mis‑written
Students often write the oxygen electrode half‑reaction as O₂ + 4e⁻ → 2O²⁻ instead of the correct form involving water and protons
The correct oxygen half‑reaction in a hydrogen fuel cell is O₂ + 4H⁺ + 4e⁻ → 2H₂O (or, in alkaline solution, O₂ + 2H₂O + 4e⁻ → 4OH⁻). Ensure the reaction includes the appropriate protons or hydroxide ions and produces water, not oxide ions.
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