State two advantages and two disadvantages of using hydrogen-oxygen fuel cells to generate electricity.
Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).
Model answer (4 marks)
Advantage 1: The only waste product is water, so no CO₂ or harmful exhaust gases are released.
Advantage 2: They are more efficient than combustion engines and can supply electricity continuously as long as fuel is supplied.
Disadvantage 1: Hydrogen is difficult and expensive to store or transport, requiring high‑pressure tanks or cryogenic storage.
Disadvantage 2: Most hydrogen is produced from fossil fuels (e.g. steam reforming of methane), so its production is not fully clean and can be costly if produced by electrolysis.
Advantage 2: They are more efficient than combustion engines and can supply electricity continuously as long as fuel is supplied.
Disadvantage 1: Hydrogen is difficult and expensive to store or transport, requiring high‑pressure tanks or cryogenic storage.
Disadvantage 2: Most hydrogen is produced from fossil fuels (e.g. steam reforming of methane), so its production is not fully clean and can be costly if produced by electrolysis.
Examiner tips
- Use the exact wording from the mark scheme (e.g. "water" and "no CO₂").
- Show both advantages and disadvantages, each in a separate sentence.
- Keep each point concise – no extra explanation needed.
Common mistakes
- Writing that the only waste is CO₂ instead of water.
- Omitting the fact that hydrogen is produced from fossil fuels or that storage is difficult.
- Using vague terms like "clean" without specifying the source of hydrogen.
Mark scheme (4 marks)
- Advantage 1: The only product/waste released is water (no carbon dioxide or polluting exhaust gases produced)
- Advantage 2: More efficient than combustion engines / produces electrical energy directly without burning fuel / continuous supply of electricity as long as fuel is supplied
- Disadvantage 1: Hydrogen is difficult/expensive to store or transport (hydrogen is a flammable/explosive gas; requires high-pressure tanks or cryogenic storage)
- Disadvantage 2: Hydrogen is mainly produced from fossil fuels (e.g. steam reforming of methane), so its production is not fully clean / expensive to produce by electrolysis using renewable energy
Key terms in this question
Related
- All Cambridge International IGCSE Chemistry (0620) revision notes →
- How to answer a "State" question →
- Decode the mark scheme abbreviations →
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