Question detail
Which comparison keeps chemistry only separate from a nearby Unit 4.5 idea?
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 comparison: says the two nearby ideas mean the same thing
- C. Incorrect comparison: uses the same evidence for exothermic and endothermic cases
- D. Incorrect comparison: ignores the direction of energy transfer
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 comparison version 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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