Science (086) — AI-generated practice question

(i) Structural difference between successive members:
Any two successive members of this homologous series differ by one –CH₂– unit (i.e., one carbon atom and two hydrogen atoms), with a difference of 14 u in molecular mass. For example, methanol (CH₃OH) and ethanol (C₂H₅OH) differ by –CH₂–.

(ii) Similar chemical properties:
All members of this series contain the same functional group –OH (hydroxyl group). Since chemical properties are determined solely by the functional group, all members show very similar chemical properties. The difference in physical properties (like boiling point and solubility) is due to the gradual increase in molecular mass along the series.

Source: Chapter 4, Section 4.2.4 – Homologous Series

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• (i) The examiner expects the key phrase "–CH₂– unit" and the mass difference of 14 u, with an example for full marks.
• (ii) The core idea is: functional group → chemical properties; molecular mass → physical properties. Both parts must be addressed. The textbook explicitly states "the chemical properties, which are determined solely by the functional group, remain similar in a homologous series."
• Avoid writing long paragraphs; crisp, pointed sentences score better in board exams.