A student claims that hydrogen-oxygen fuel cells are better for the environment than power stations that burn coal to generate electricity. Evaluate this claim.
Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).
Model answer (4 marks)
Fuel cells produce only water as a product, so at the point of use they emit no carbon dioxide or other polluting gases.
Coal‑burning power stations release large amounts of CO₂, and often SO₂ and NOx, contributing to air pollution and climate change.
However, the environmental advantage of fuel cells depends on how the hydrogen is produced. If it is made by electrolysis using electricity from fossil fuels, or by reforming natural gas, the overall CO₂ emissions can be significant.
Therefore the claim is partly valid: fuel cells are cleaner at the point of use, but their overall benefit depends on the hydrogen source. If hydrogen is produced from renewable energy, the claim is fully supported; otherwise it is only partially justified.
Coal‑burning power stations release large amounts of CO₂, and often SO₂ and NOx, contributing to air pollution and climate change.
However, the environmental advantage of fuel cells depends on how the hydrogen is produced. If it is made by electrolysis using electricity from fossil fuels, or by reforming natural gas, the overall CO₂ emissions can be significant.
Therefore the claim is partly valid: fuel cells are cleaner at the point of use, but their overall benefit depends on the hydrogen source. If hydrogen is produced from renewable energy, the claim is fully supported; otherwise it is only partially justified.
Examiner tips
- Mention the zero emissions at the point of use first to gain full marks for that point.
- Include the counter‑argument about hydrogen production to show balanced evaluation.
- Conclude clearly that the claim is only fully valid if hydrogen is renewable.
- Use the exact terminology: ‘CO₂’, ‘SO₂’, ‘NOx’, ‘electrolysis’, ‘reforming’.
Common mistakes
- Assuming all hydrogen is produced renewably and ignoring the production stage.
- Forgetting to mention the pollutants released by coal power stations.
- Using vague terms like ‘cleaner’ without specifying the gases involved.
Mark scheme (4 marks)
- Fuel cells produce only water as a product / no carbon dioxide or polluting gases produced during operation
- Coal-burning power stations release carbon dioxide (and/or sulfur dioxide / nitrogen oxides), contributing to pollution or climate change
- Counter-argument: hydrogen is often produced by electrolysis or reforming of fossil fuels / the production of hydrogen may itself generate carbon dioxide or use electricity from non-renewable sources
- Balanced conclusion: claim is partly valid / fuel cells are better at point of use but overall environmental benefit depends on the hydrogen source / if hydrogen is from renewables then the claim is fully supported
Key terms in this question
Related
- All Cambridge International IGCSE Chemistry (0620) revision notes →
- How to answer a "Evaluate" question →
- Decode the mark scheme abbreviations →
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