For binary solution of two liquids, A and B
Match List-I with List-II
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List-I Inter-molecular interaction |
List-II Behavior |
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(A). A-A & B-B are nearly equal to A-B |
(I). Negative deviation from Raoult's Law |
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(B). A-A & B-B are stronger compared to A-B |
(II). Azeotropes |
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(C). A-A & B-B are weaker compared to A-B |
(III). Positive deviation from Raoult's Law |
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(D). Very strong A-B interaction |
(IV). No deviation from Raoult's Law |
Choose the correct answer from the options given below:
Answer & explanation
Correct answer: option 1
The correct answer is Option (1) → (A)-(IV), (B)-(III), (C)-(I), (D)-(II)
Whether a mixture of two liquids A and B obeys Raoult’s law depends on the A–B attractions compared with the A–A and B–B attractions. Weaker A–B attractions let molecules escape more easily, so the vapour pressure is higher than Raoult’s law predicts; stronger A–B attractions hold them back, so it is lower. When the deviation is very large, the mixture forms an azeotrope.
(A). A-A & B-B are nearly equal to A-B — This matches (IV). No deviation from Raoult’s Law. Such a mixture is an ideal solution, with \( \Delta_{mix}H = 0 \) and \( \Delta_{mix}V = 0 \), for example n-hexane and n-heptane, or benzene and toluene.
(B). A-A & B-B are stronger compared to A-B — This matches (III). Positive deviation from Raoult’s Law. Molecules escape more easily from the mixture, as when acetone is added to ethanol and breaks some of its hydrogen bonds.
(C). A-A & B-B are weaker compared to A-B — This matches (I). Negative deviation from Raoult’s Law. The stronger A–B attractions lower the escaping tendency, as in chloroform and acetone, which hydrogen bond with each other.
(D). Very strong A-B interaction — This matches (II). Azeotropes. A very large negative deviation gives a maximum boiling azeotrope, such as nitric acid and water (about 68% nitric acid), which boils at a constant temperature with the same composition in the liquid and the vapour.
Shortcut: (A)-(IV) appears in Options (1) and (2); (C)-(I) then leaves only Option (1).