Ethanol can be oxidised to form a carboxylic acid. Explain what is meant by the term carboxylic acid, name the carboxylic acid formed from ethanol, identify its functional group, state one typical chemical property of carboxylic acids, and name the homologous series member with four carbon atoms.
Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).
Alcohols such as ethanol are widely used as solvents and fuels. Under certain conditions, ethanol can be further oxidised to produce a member of another homologous series.
Model answer (5 marks)
A carboxylic acid is an organic compound that contains the functional group –COOH.
The carboxylic acid formed from the oxidation of ethanol is ethanoic acid.
Its functional group is the carboxyl group –COOH.
A typical chemical property of carboxylic acids is that they are acidic – they react with metals, carbonates and bases, turn litmus red and have a pH below 7.
The homologous series member with four carbon atoms is butanoic acid.
The carboxylic acid formed from the oxidation of ethanol is ethanoic acid.
Its functional group is the carboxyl group –COOH.
A typical chemical property of carboxylic acids is that they are acidic – they react with metals, carbonates and bases, turn litmus red and have a pH below 7.
The homologous series member with four carbon atoms is butanoic acid.
Examiner tips
- Define the functional group first, then give the specific acid name; use the term ‘carboxyl group’ as acceptable.
- Show the acid’s acidic property in one sentence – e.g. ‘reacts with metals to give H2’ – to secure the property mark.
- Mention the homologous series member (butanoic acid) to get the final point.
Mark scheme (5 marks)
- Carboxylic acids are organic compounds containing the functional group –COOH
- The carboxylic acid formed from the oxidation of ethanol is ethanoic acid
- The functional group of a carboxylic acid is –COOH (accept: carboxyl group)
- Carboxylic acids have typical acidic properties, e.g. they react with metals / carbonates / bases / turn litmus red / have a pH below 7
- The member of the carboxylic acid homologous series with four carbon atoms is butanoic acid
Key terms in this question
carboxylic acids · functional group · homologous series · oxidised
Related
- All OCR A-Level Chemistry A (H432) revision notes →
- How to answer a "Explain" question →
- Decode the mark scheme abbreviations →
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