JEE Chemistry 2025 Question with Solution

Given: The question asks which binary mixture does not show minimum boiling azeotrope behavior.

Find: The mixture that does not form a minimum boiling azeotrope.

Minimum boiling azeotropes are associated with positive deviation from Raoult's law, which occurs when unlike molecular interactions are weaker than like molecular interactions. In contrast, negative deviation is associated with maximum boiling azeotropes and stronger unlike interactions.

Evaluate the options:

1. $CS_2 + CH_3COCH_3$ forms a minimum boiling azeotrope.
2. $H_2O + CH_3COC_2H_5$ forms a minimum boiling azeotrope.
3. $C_6H_5OH + C_6H_5NH_2$ shows strong intermolecular hydrogen bonding and negative deviation from Raoult's law, so it does not show minimum boiling azeotrope behavior.
4. $CH_3OH + CHCl_3$ forms a minimum boiling azeotrope.

Therefore, the correct option is C.

Given: Minimum boiling azeotropes arise when the solution shows positive deviation from Raoult's law.

Find: Which given pair does not behave as a minimum boiling azeotrope.

Key idea:

• Weaker interaction between unlike molecules $\Rightarrow$ positive deviation $\Rightarrow$ minimum boiling azeotrope.
• Stronger interaction between unlike molecules $\Rightarrow$ negative deviation $\Rightarrow$ maximum boiling azeotrope.

Now analyze each pair:

• $CS_2 + CH_3COCH_3$: non-polar and polar components together show positive deviation, so this pair forms a minimum boiling azeotrope.
• $H_2O + CH_3COC_2H_5$: disruption of strong water-water interaction leads to azeotropic behavior of minimum boiling type.
• $C_6H_5OH + C_6H_5NH_2$: phenol and aniline can form strong intermolecular hydrogen bonding with each other. This causes negative deviation and corresponds to maximum boiling behavior, not minimum boiling behavior.
• $CH_3OH + CHCl_3$: this pair is known to form a minimum boiling azeotrope.

Hence, the mixture that does not show minimum boiling azeotrope behavior is $C_6H_5OH + C_6H_5NH_2$. Therefore, the correct option is C.