Question detail
Which structural formula represents propanoic acid in the first four carboxylic acids?
Try the question, check the answer, then read the explanation to understand the curriculum point.
At a glance
MCQ
Type
practice
Style
Topic
Reactions of alkenes and alcohols (chemistry only)
Question
- A. HCOOH
- B. CH3COOH
- C. CH3CH2COOH
- D. CH3CH2CH2COOH
Answer
The correct option is CH3CH2COOH.
Explanation
The correct option is CH3CH2COOH. CH3CH2COOH is propanoic acid because it has three carbon atoms and the carboxylic acid functional group, COOH. HCOOH is methanoic acid, CH3COOH is ethanoic acid, and CH3CH2CH2COOH is butanoic acid. This keeps the homologous-series order separate from structural formula recognition in AQA GCSE Chemistry organic chemistry.
Common mistake
Mis‑naming the first four carboxylic acids
Students often write the first four members of the carboxylic acid series as methanoic, ethanoic, propanoic, and butanoic acids but mistakenly use the suffix –ic acid for all, forgetting that the first acid is correctly named methanoic acid (not methanoic acid).
Remind students that the correct systematic names are methanoic acid, ethanoic acid, propanoic acid and butanoic acid, and that the –ic acid suffix is applied to the parent alkane name (methane, ethane, propane, butane) with the –oic acid ending added.
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