CC7.2 — Combustion (Edexcel 1SC0)
Complete combustion
Hydrocarbon + excess oxygen → carbon dioxide + water CH₄ + 2O₂ → CO₂ + 2H₂O
Blue flame. Products: CO₂ and H₂O only.
Incomplete combustion
Hydrocarbon + insufficient oxygen → carbon monoxide + carbon (soot) + water (+ sometimes CO₂)
Yellow/orange flame; produces soot; very dangerous — CO is a colourless, odourless, toxic gas.
Pollutants from burning fossil fuels
| Pollutant | Source | Effect |
|---|---|---|
| CO₂ | Complete combustion | Greenhouse gas → climate change |
| CO | Incomplete combustion | Toxic; prevents haemoglobin from carrying O₂ |
| Soot (C) | Incomplete combustion | Particulate pollution; respiratory problems |
| SO₂ | Sulfur impurities in fuel | Acid rain (SO₂ + H₂O + O₂ → H₂SO₄) |
| NOₓ | High temperature combustion in air | Acid rain; smog; respiratory irritant |
Catalytic converters
Convert harmful pollutants from car exhausts: 2CO + 2NO → 2CO₂ + N₂ (platinum/palladium catalyst) Unburned hydrocarbons are also oxidised to CO₂ and H₂O.
AI-generated · claude-opus-4-7 · v3-edexcel-combined-science