Sulfur dioxide and carbon monoxide are both pollutants produced when fossil fuels are burned. Describe how each gas is produced and explain one harmful effect of each gas on either human health or the environment.

Edexcel GCSE Chemistry (1CH0) — 8.1 Fuels · Describe · 4 marks · View as Markdown

Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).

Model answer (4 marks)

Sulphur dioxide is produced when fossil fuels containing sulphur impurities are burnt, releasing
SO₂. It reacts with water vapour in the atmosphere to form sulphuric acid, producing acid rain that damages ecosystems, harms living organisms and corrodes buildings.

Carbon monoxide is produced during incomplete combustion when there is insufficient oxygen. It is toxic to humans because it binds to haemoglobin, preventing blood from carrying oxygen and can lead to unconsciousness or death.

Examiner tips

  • Use the exact terms ‘sulphur dioxide’, ‘carbon monoxide’, ‘incomplete combustion’, ‘acid rain’, ‘haemoglobin’. Show the cause–effect chain for each gas. Keep the answer concise – 4 marks allow one sentence per point.

Common mistakes

  • Writing ‘sulfur’ instead of ‘sulphur’. Failing to mention incomplete combustion for CO. Mixing up the harmful effect of SO₂ with that of CO.

Mark scheme (4 marks)

  1. Sulfur dioxide is produced when fossil fuels containing sulfur impurities are burned (combusted)
  2. Sulfur dioxide causes acid rain (by reacting with water vapour in clouds) which damages ecosystems / harms living organisms / corrodes buildings
  3. Carbon monoxide is produced during incomplete combustion (when there is insufficient oxygen)
  4. Carbon monoxide is toxic to humans because it prevents the blood from carrying oxygen (leading to death / unconsciousness)

Key terms in this question

sulfur dioxide · carbon monoxide · pollutants · fossil fuels

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