Vapour pressure trend (revisited):\nFor liquids of similar chemical nature at a given temperature, vapour pressure generally ________ with increasing molecular weight.

Introduction / Context:
This is the same volatility principle assessed again to reinforce understanding: within a homologous series, heavier molecules have stronger intermolecular attractions, thus lower vapour pressures at the same temperature.

Given Data / Assumptions:

• Chemically similar liquids (e.g., homologs).
• Constant temperature.

Concept / Approach:
Greater molecular size and surface area strengthen dispersion forces, reducing the tendency to escape into vapour, so vapour pressure decreases with molecular weight.

Step-by-Step Solution:
Fix temperature; compare homologs.Heavier member → stronger cohesion → lower vapour pressure.Answer: decreases.

Verification / Alternative check:
Antoine correlations across homologous series confirm this trend.

Why Other Options Are Wrong:
Options a, c, d, e contradict well-established behaviour for similar liquids.

Common Pitfalls:
Overgeneralizing to dissimilar chemistries; stick to similar nature.

Final Answer:
decreases