JEE Main 2025 Apr 8 Shift 2, Chemistry Q8: Vapour Pressure Of A Solution

JEE Main2025Apr 8, Shift 2Chemistry

Which of the following binary mixture does not show the behaviour of minimum boiling azeotropes?

A
H $_{2}$ O + CH $_{3}$ COC $_{2}$ H $_{5}$
B
C $_{6}$ H $_{5}$ OH + C $_{6}$ H $_{5}$ NH $_{2}$
C
CS $_{2}$ + CH $_{3}$ COCH $_{3}$
D
CH $_{3}$ OH + CHCl $_{3}$

Solution

A minimum boiling azeotrope arises from positive deviation from Raoult's law, where unlike-molecule interactions are weaker than like-molecule interactions.

Phenol ( $C_{6} H_{5} O H$ ) and aniline ( $C_{6} H_{5} N H_{2}$ ) can hydrogen bond strongly with one another, so this pair instead shows negative deviation from Raoult's law.

Negative deviation lowers the vapour pressure of the mixture below the ideal value, which raises the boiling point above that of either pure component, producing a maximum boiling azeotrope rather than a minimum boiling one.

Therefore the C $_{6}$ H $_{5}$ OH + C $_{6}$ H $_{5}$ NH $_{2}$ mixture is the one that does not show minimum boiling azeotropic behaviour, matching option (2).

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JEE Main 2025 Apr 8 Shift 2, Chemistry Q8: Vapour Pressure Of A Solution

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