Question

From the following list, identify the properties which are equal in both vapor and liquid phases at equilibrium:
(A) Temperature
(B) Density
(C) Enthalpy
(D) Chemical potential
Choose the \textbf{correct} answer from the options given below:

• A. A and B
• B. A and C
• C. C and D
• D. A and D

Hint:

At phase equilibrium, temperature and chemical potential are equal across co-existing phases.

Answer 1

The Correct Option is D

Step 1: Recall equilibrium conditions.
At phase equilibrium (liquid–vapor equilibrium), certain intensive properties are equal in both phases. Temperature must be the same for equilibrium, and chemical potential must also be equal for equilibrium to exist.

Step 2: Analyze each property.
- (A) Temperature: Equal in both phases at equilibrium.
- (B) Density: Not equal; liquid is denser than vapor.
- (C) Enthalpy: Different for vapor and liquid.
- (D) Chemical potential: Must be equal in both phases at equilibrium.

Step 3: Conclusion.
The correct answer is (4) A and D.