A negative deviation from Raoult law is expected when
A{'text': 'A-B interactions are weaker than A-A and B-B', 'label': 'A'}
B{'text': 'A-B interactions are stronger than A-A and B-B', 'label': 'B'}
C{'text': 'A and B are chemically identical', 'label': 'C'}
D{'text': 'A and B do not mix at all', 'label': 'D'}
Answer & Solution
Correct answer: B. {'text': 'A-B interactions are stronger than A-A and B-B', 'label': 'B'}
1. Non-ideal solutions can deviate from Raoult law positively or negatively.
2. Negative deviation happens when A-B intermolecular forces are STRONGER than A-A and B-B.
3. Stronger cross interactions reduce vapour pressure below the ideal prediction.
4. Example: HCl and water form a negatively deviating mixture (maximum boiling azeotrope).
_Source: NCERT Class 12 Chemistry, Unit 1 "Solutions", §1.5_
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