Specification Point 4.31C (Paper 2C Only):
Know that Ethanol can be oxidised by: burning in air or Oxygen (complete combustion), reaction with oxygen in the air to form Ethanoic acid (microbial oxidation), heating with Potassium dichromate (vi) in dilute Sulfuric acid to form Ethanoic acid
Oxidation: The loss of electrons and gain in oxygen.
Oxidation of Ethanol
*complete combustion of ethanol:
Ethanol can be oxidised by the process of complete combustion as ethanol burns when heated in air or oxygen:
Ethanol + Oxygen → Carbon dioxide + water
C2H5OH 3O2 2CO2 3H2O
- The microbial oxidation of ethanol occurs once a bottle of wine is opened.
- This is caused by the bacteria in the air (acetobacter) using atmospheric oxygen from air to oxidise the ethanol in wine, producing a weak solution of ethanoic acid (also known as acetic acid):
Ethanol + Oxygen → Ethanoic Acid + Water
C2H5OH 3O2 CH3COOH 3H2O
So once a bottle of wine has been opened, it can quickly turn into vinegar due to the large number of bacteria in the air.
*Heating with potassium dichromate (vi) in dilute Sulfuric acid:
- Ethanol can be oxidised by heating it with an oxidising agent such as Potassium dichromate (vi) in dilute Sulphuric acid.
- The alcohol is oxidized to a carboxylic acid.
- If the oxidation occurs, then the orange solution containing the dichromate (vi) ions is reduced to a green solution containing chromium (ii) ions:
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