5.2.3

Combustion

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Combustion

Combustion is a fancy name for burning. When you burn a hydrocarbon, you can have complete combustion or incomplete combustion.

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Complete combustion

  • Complete combustion gives a blue flame.
  • Complete combustion produces only carbon dioxide and water.
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Incomplete combustion

  • Incomplete combustion gives an orange smoky flame.
    • The orange colour is due to small particles of pure carbon glowing red hot.
  • Incomplete combustion gives some carbon dioxide, some water, but also pure carbon, hydrocarbons, and carbon monoxide.
  • Incomplete combustion is more likely with longer chain alkanes, as they need more oxygen to combust completely.

Harmful Effects of Combustion

Combustion can cause the production of some nasty chemicals.

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The internal combustion engine

  • The combustion of alkanes powers our cars via the internal combustion engine.
  • Common impurities from the internal combustion engine are:
    • Nitrous oxides (NOx).
    • Unburned hydrocarbons.
    • Carbon monoxide.
  • Nitrous oxides react to form ozone at ground level.
    • Ozone irritates eyes and can cause lung damage.
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Flue gases

  • Flue gases are the gases that come out of chimneys. They are also produced as industrial waste.
  • Flue gases often contain sulfur dioxide.
    • Sulfur dioxide dissolves in water to make sulfuric acid. This then falls as acid rain, which destroys trees and vegetation.
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Removing these chemicals

  • We can remove sulfur dioxide by reacting with calcium oxide or calcium carbonate.
  • This is because sulfur dioxide is acidic and calcium oxide is basic. The balanced equation for the process is:
    • CaO +SO2 → CaSO3
  • Catalytic converters can remove unburned hydrocarbons and nitrous oxides from fuel.

Jump to other topics

1Physical Chemistry

2Physical Chemistry 2 (A2 Only)

3Inorganic Chemistry

4Inorganic Chemistry 2 (A2 Only)

5Organic Chemistry 1

6Organic Chemistry 2 (A2 Only)

6.1Optical Isomerism (A2 Only)

6.2Aldehydes & Ketones (A2 Only)

6.3Carboxylic Acids & Esters (A2 Only)

6.4Aromatic Chemistry (A2 Only)

6.5Amines (A2 Only)

6.6Polymers (A2 Only)

6.7Biological Organic (A2 Only)

6.8Organic Synthesis (A2 Only)

6.9NMR Spectroscopy (A2 Only)

6.10Chromatography (A2 Only)

6.11A-A* (AO3/4) - Organic 2

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