Which of the following is NOT a colligative property?
A{'text': 'Elevation of boiling point', 'label': 'A'}
B{'text': 'Depression of freezing point', 'label': 'B'}
C{'text': 'Vapour pressure lowering', 'label': 'C'}
D{'text': 'Refractive index', 'label': 'D'}
Answer & Solution
Correct answer: D. {'text': 'Refractive index', 'label': 'D'}
1. Colligative properties depend on the number of solute particles, not their nature.
2. Boiling-point elevation, freezing-point depression and vapour-pressure lowering are all colligative.
3. Osmotic pressure is also colligative.
4. Refractive index depends on the identity of the substances, not just particle count, so it is not colligative.
_Source: NCERT Class 12 Chemistry, Unit 1 "Solutions", §1.6_
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