Fuels from crude oil
- Crude oil contains many different compounds that boil at different temperatures.
- These burn under differen conditiions and so crude oil needs to be separated to make useful fuels.
- Distillation can be used to separate mixtures of liquids.
- Fractional distillation works because the different fractions boil (vaporise) at different temperatures.
- Most of the compounds in crude oil are hydrocarbons - they only conatin hydrogen & carbon.
- Alkanes are saturated hydrocarbons. They contain as many hydrogen atoms as possible in their molecules.
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- Crude oil is separated into fractions using fractional distillation.
- Each fraction contains compounds with similar boiling points.
- The larger the molecule, the higher the boiling point of the hydrocarbon.
- Fractions with lower boiling points are less viscous (sticky/thick) and burn more easily, e.g. petrol.
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- Burning hydrocarbons in plenty of air produces carbon dioxide and water.
- Burning hydrocarbons in a limited supply of air may produce carbon monoxide and solid particles.
- Any sulfur compounds in the fuel burn to produce sulfur dioxide.
- Sulfur dioxide causes acid rain.
- Oxides of nitrogen can be formed when fuels burn under extreme conditions.
- Nitrogen oxides also cause acid rain.
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