Science (086) — AI-generated practice question

The student's argument is partially correct but partially wrong.

What is correct: Both butanol and ethanol belong to the same homologous series (alcohols) and share the same functional group (–OH). Therefore, their chemical properties are similar — both react with sodium to release hydrogen, and undergo similar reactions.

What is incorrect: Physical properties such as boiling point and solubility change across a homologous series. As molecular mass increases (butanol > ethanol), boiling point increases. Solubility in water also shows a gradation — ethanol is completely miscible with water, while butanol has lower solubility. These physical properties differ because each successive member differs by a –CH₂– unit, increasing molecular mass.

Source: Chapter 4, Section 4.2.4 — Homologous Series

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Examiners look for three things here:

1. Identifying what is correct — same functional group → similar chemical properties.
2. Identifying what is wrong — boiling point and solubility are physical properties that change with molecular mass (gradation).
3. Reason — each member differs by –CH₂–, so molecular mass increases → boiling point increases, solubility decreases.

The key textbook line is: "As the molecular mass increases in any homologous series, a gradation in physical properties is seen… But the chemical properties… remain similar." Quote or paraphrase this for full marks.