Question detail
Which exam-check sentence would most directly answer a question about chemistry only?
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 exam-check: gives a memorised phrase without subtopic detail
- C. Incorrect exam-check: omits the key Energy changes vocabulary
- D. Incorrect exam-check: answers a different objective from 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) Explain that the fuel is oxidised electrochemically within a fuel cell. This exam-check 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
Misidentifying the Oxidation Step
Students often think the fuel (hydrogen) is reduced at the anode and the oxygen is oxidised at the cathode, confusing the direction of electron flow in a fuel cell.
In a hydrogen fuel cell, the fuel (hydrogen) is oxidised at the anode (H₂ → 2H⁺ + 2e⁻) and the oxygen is reduced at the cathode (O₂ + 4H⁺ + 4e⁻ → 2H₂O). The oxidation of hydrogen is the electrochemical reaction that generates electrons, not the reduction of oxygen.
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