AQA AS Chemistry

Revision Notes

3.5.4 Combustion of Alcohols

Combustion of Alcohols

Combustion of alcohols

  • Alcohols react with oxygen in the air when ignited and undergo complete combustion to form carbon dioxide and water

alcohol + oxygen → carbon dioxide + water

 

Hydroxy Compounds Combustion of Alcohols, downloadable AS & A Level Chemistry revision notes

Complete combustion of alcohols to produce carbon dioxide and water

  • Lower alcohols burn with an almost invisible flame and make good fuels
  • Ethanol can be produced sustainably as a fuel by the fermentation of sugars
  • However, the energy density (the amount of energy in kJ per kg of fuel) is lower than gasoline so cars that run on ethanol must either have a larger fuel tank or fill up more often
  • Blending ethanol with gasoline or diesel increases the energy density and makes it safer in case of fires as it is easier to see the flames compared to pure ethanol burning
  • However, the are socio-economic concerns about using large quantities of farm land to produce crops for fermentation, which could be better used for food production

Exam Tip

Be careful when balancing equations for the combustion of alcohols, as students often forget to count the oxygen in the alcohol.

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