Question

If two liquids A and B form a minimum boiling azeotrope at some specific composition then:

• A. A-B interactions are stronger than those between A-A or B-B
• B. Shows a large negative deviation from Raoult's law
• C. Total vapour pressure of solution decreases
• D. Shows a large positive deviation from Raoult's law

Answer 1

The correct option is D Shows a large positive deviation from Raoult's law

Liquid mixture of two miscible liquids which distill over without changes in composition is called Azeotropic mixture.
These mixture boils at constant temperature while the composition remains constant.

Minimum boiling azeotrope means the liquid mixture have lower boiling point than its individual components. Thus, the interaction between A-B is lesser than the interaction between A-A and B-B. This makes the vapour pressure of liquid mixture higher than the initial pressure. As the result their boiling point is lower than the individual liquids.
$P_T>X_A.p_A+X_B.p_B$
Thus, it shows a large positive deviation from Raoult's law.