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wise otter.Chemistry
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Maintaining Air Quality

Topic 2 of 3

Explain harm through a chemical cause

Link the pollutant to the process and then the effect.

O-Level 5086 / 5088 (2026) / SEC G3 K326 / K328 (2027)

Explain harm through a chemical cause

Link the pollutant to the process and then the effect.

Carbon monoxide binds strongly to haemoglobin and reduces the blood's ability to carry oxygen. It is not the same hazard as carbon dioxide's role in climate change. Because incomplete combustion can produce CO, a fuel burning does not guarantee that its exhaust contains only carbon dioxide and water.

Nitrogen dioxide and sulfur dioxide react in the atmosphere with water and oxygen to produce acidic substances that enter rain. Acid rain can damage plants and aquatic ecosystems and attack buildings containing carbonate stone. These gases also irritate the respiratory system; health effects are not confined to rainwater.

For a limestone surface, carbonate reacts with acid: CaCO3(s) + 2H+(aq) -> Ca2+(aq) + H2O(l) + CO2(g). Solid material is gradually lost. This connects the visible damage to an acid-carbonate reaction rather than merely saying that pollution is bad.

Worked example

Use source evidence

Two fuels release the same energy. One contains much more sulfur. What additional air-quality concern does it create?

  1. Combustion can convert its sulfur compounds into sulfur dioxide.
  2. Sulfur dioxide contributes to acid rain and respiratory irritation.
  3. Equal useful energy does not imply equal pollutant emissions.
Answer

The higher-sulfur fuel can create greater SO2 pollution; compare sulfur content and any treatment of the exhaust.

Check your understandingWhy is "carbon monoxide causes acid rain" the wrong explanation here?Think it through, then reveal the answer
The prescribed acid-rain gases are nitrogen dioxide and sulfur dioxide. Carbon monoxide's key effect here is toxicity through impaired oxygen transport.