Q1. [2] straightforward exam-ready
State two characteristics of a homologous series. A compound belonging to the carboxylic acid series has the molecular formula C₃H₆O₂. Write the molecular formulae of the next two higher members of this series.
Generated by claude-sonnet-4-6 · 2026-06-26 01:07 · grounding rag
Model Answer
Two characteristics of a homologous series:
- All members have the same functional group and similar chemical properties.
- Successive members differ by a –CH₂– unit (molecular mass difference of 14 u).
Next two higher members of C₃H₆O₂ (carboxylic acid series):
- C₄H₈O₂ (Butanoic acid)
- C₅H₁₀O₂ (Pentanoic acid)
Source: Carbon and its Compounds, Section 4.2.4 – Homologous Series
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Explanation
- The question has two parts — state characteristics first, then write the formulae.
- Each successive member of a homologous series adds one –CH₂– unit: C₃H₆O₂ → C₄H₈O₂ → C₅H₁₀O₂.
- The general formula for carboxylic acids is CₙH₂ₙO₂; apply it to n = 4 and n = 5.
- Examiners look for both characteristics clearly stated and both formulae correct. Names are a bonus but formulae are essential.