Ethanoic acid is a carboxylic acid found in vinegar. Describe the chemical properties of ethanoic acid, including how it reacts with carbonates and with alcohols.
Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).
Ethanoic acid (CH₃COOH) is a weak acid. It can undergo several characteristic reactions, including one that produces a sweet-smelling product used in the food industry.
Model answer (5 marks)
Ethanoic acid (CH₃COOH) is a weak acid – it does not fully dissociate in water and only partially ionises to CH₃COO⁻ and H⁺.
With a carbonate (e.g. Na₂CO₃) it reacts to give carbon dioxide, water and the corresponding ethanoate salt:
CH₃COOH + Na₂CO₃ → 2 NaCH₃COO + CO₂↑ + H₂O.
With an alcohol (R–OH) it undergoes esterification in the presence of an acid catalyst:
CH₃COOH + R–OH ⇌ CH₃COOR + H₂O.
The reaction is reversible and water is produced.
With a carbonate (e.g. Na₂CO₃) it reacts to give carbon dioxide, water and the corresponding ethanoate salt:
CH₃COOH + Na₂CO₃ → 2 NaCH₃COO + CO₂↑ + H₂O.
With an alcohol (R–OH) it undergoes esterification in the presence of an acid catalyst:
CH₃COOH + R–OH ⇌ CH₃COOR + H₂O.
The reaction is reversible and water is produced.
Examiner tips
- Mention that ethanoic acid is weak and only partially ionises
- Show the carbonate reaction with CO₂ effervescence and salt formation
- State the esterification equation, note acid catalyst and reversibility
Common mistakes
- Saying ethanoic acid is a strong acid
- Omitting the carbonate salt product
- Forgetting that esterification is reversible and requires a catalyst
Mark scheme (5 marks)
- Ethanoic acid is a weak acid / does not fully dissociate / partially ionises in water
- Ethanoic acid reacts with carbonates to produce carbon dioxide (gas) / effervescence / bubbles
- Ethanoic acid reacts with carbonates to also produce a salt (ethanoate salt) and water
- Ethanoic acid reacts with an alcohol in an esterification reaction / to form an ester
- Water is also produced in the reaction between ethanoic acid and an alcohol / an acid catalyst is needed / the reaction is reversible
Key terms in this question
Related
- All Eduqas A-Level Chemistry revision notes →
- How to answer a "Describe" question →
- Decode the mark scheme abbreviations →
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