NEET Solutions — Set 12

Question 1

What is the freezing point depression of a 0.2 molal solution of a non-electrolyte in water? ($ K_f = 1.86 \, \text{K kg mol}^{-1} $)

Accepted Answer

$ \Delta T_f = K_f \cdot m $. $ \Delta T_f = 1.86 \times 0.2 = 0.372 \, \text{K} $.

Question 2

A solution reduces the vapor pressure of a solvent from 35 mm Hg to 33 mm Hg. What is the mole fraction of the solute?

Accepted Answer

$ \frac{p^0 - p}{p^0} = x_{\text{solute}} $. $ \frac{35 - 33}{35} = \frac{2}{35} \approx 0.0571 $.

Question 3

A 0.15 molal KCl solution has a van’t Hoff factor of 1.85. What is the freezing point depression? ($ K_f = 1.86 \, \text{K kg mol}^{-1} $)

Accepted Answer

$ \Delta T_f = i \cdot K_f \cdot m $. $ \Delta T_f = 1.85 \times 1.86 \times 0.15 \approx 0.5162 \, \text{K} $.

NEET Chemistry: Solutions — Practice Set 12