Question

Calculate cryoscopic constant of solvent if depression in freezing point of 0.18 m solution of nonvolatile solute is 0.2 K

• A. 1.73 K $kg~mol^{-1}$
• B. 1.50 K $kg~mol^{-1}$
• C. 1.11 K $kg~mol^{-1}$
• D. 1.92 K $kg~mol^{-1}$

Hint:

Cryoscopic constant ($K_f$) is the depression in freezing point for 1 molal solution.

Answer 1

The Correct Option is C

Step 1: Concept
Depression in freezing point is a colligative property.

Step 2: Formula
$\Delta T_f = K_f \times m$

Step 3: Analysis
- $0.2 = K_f \times 0.18$
- $K_f = \frac{0.2}{0.18} = \frac{20}{18} = 1.111$

Step 4: Conclusion
Hence, the cryoscopic constant ($K_f$) is 1.11 K $kg~mol^{-1}$. Final Answer: (C)