JEE Main · 2004 · 24 Apr 2004 · Offline · Solutions

Which of the following liquid pairs shows a positive deviation from Raoult's law?

(A)Water - hydrochloric acid
(B)Acetone - chloroform
(C)Water - nitric acid
(D)Benzene - methanol✓ Correct

Answer: (D)

Solution

A positive deviation from Raoult's law shows up when unlike molecules attract one another less strongly than like molecules do, pushing the vapour pressure above the ideal value. Stirring benzene into methanol breaks apart methanol's hydrogen-bonded network while offering only feeble benzene-methanol attraction, so the escaping tendency climbs and the benzene-methanol pair deviates positively. The acetone-chloroform pair does the reverse, deviating negatively through hydrogen bonding between the two.

JEE Main · 2004 · 24 Apr 2004 · Offline · Single correct option

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