Propanoic acid is a member of the carboxylic acids homologous series. A student adds a small piece of calcium carbonate to a sample of propanoic acid. Describe what the student would observe, name the type of reaction taking place, and give the names of the three products formed.

Pearson Edexcel International GCSE Chemistry (4CH1) — 4.6 Carboxylic acids · Describe · 4 marks · View as Markdown

Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).

Model answer (4 marks)

Effervescence (bubbles) is observed as the calcium carbonate reacts with the propanoic acid.
The solid calcium carbonate dissolves.
The reaction is a neutralisation (acid–base) reaction.
The three products are calcium propanoate, water and carbon dioxide.

Examiner tips

  • Use the word "effervescence" or "bubbles" to show gas evolution. State that the solid disappears. Identify the reaction as neutralisation. Name all three products exactly: calcium propanoate, water, carbon dioxide.

Common mistakes

  • Writing "CO₂" instead of "carbon dioxide". Omitting the solid’s disappearance. Calling the reaction a "decomposition" instead of a neutralisation.

Mark scheme (4 marks)

  1. Effervescence / bubbles / fizzing observed (accept: gas is produced)
  2. The solid (calcium carbonate) dissolves / disappears
  3. Neutralisation / acid–base reaction (accept: salt formation)
  4. Names all three products correctly: calcium propanoate AND water AND carbon dioxide

Key terms in this question

carboxylic acids · homologous series

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