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A solution showing positive deviation from Raoult's law has:
AA-B intermolecular interactions weaker than A-A and B-B, leading to higher total vapour pressure than the ideal value
BNo mixing at the molecular level
CThe same intermolecular interactions as the pure components
DA-B intermolecular interactions stronger than A-A and B-B
Answer & Solution
Correct answer: A. A-B intermolecular interactions weaker than A-A and B-B, leading to higher total vapour pressure than the ideal value
Positive deviation from Raoult's law: $p_T > p_T^\text{ideal}$. This happens when A-B interactions are weaker than the average of A-A and B-B, so molecules escape more easily into the vapour phase. Example: ethanol + water, acetone + carbon disulphide. Negative deviation (e.g. acetone + chloroform) corresponds to stronger A-B interactions.
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