Q16 / 150 · MHT CET 2026 (15 April Shift 2) · Chemistry
If a 0.4 molal solution of a nonvolatile solute in organic solvent decreases its freezing point by 2.4 K., then the molal depression constant of solvent will be
- A$3.0\ \text{K kg mol}^{-1}$
- B$4.0\ \text{K kg mol}^{-1}$
- C$5.0\ \text{K kg mol}^{-1}$
- Correct answerD$6.0\ \text{K kg mol}^{-1}$
Solution
Using the formula for depression in freezing point:
$\Delta T_f = K_f \times m$
Given $\Delta T_f = 2.4$ K and $m = 0.4$ mol kg$^{-1}$.
Substituting the values:
$2.4 = K_f \times 0.4$
$K_f = \dfrac{2.4}{0.4} = 6.0$ K kg mol$^{-1}$
Answer: $6.0\ \text{K kg mol}^{-1}$
$\Delta T_f = K_f \times m$
Given $\Delta T_f = 2.4$ K and $m = 0.4$ mol kg$^{-1}$.
Substituting the values:
$2.4 = K_f \times 0.4$
$K_f = \dfrac{2.4}{0.4} = 6.0$ K kg mol$^{-1}$
Answer: $6.0\ \text{K kg mol}^{-1}$
Hence, the correct answer is option: 'D'.