Question

The relative lowering of vapor pressure of an aqueous solution containing a non-volatile solute is 0.0225. The mole fraction of the non-volatile solute is:

• A. 0.80
• B. 0.725
• C. 0.15
• D. 0.0225

Hint:

For dilute solutions, the mole fraction of solute can be approximated as the relative lowering of vapor pressure.

Answer 1

The Correct Option is D

Relative lowering of vapor pressure is given by Raoult’s Law: \[ \frac{P_0 - P}{P_0} = X_B \] where: - \( P_0 \) is the vapor pressure of pure solvent, - \( P \) is the vapor pressure of the solution, - \( X_B \) is the mole fraction of the solute. Since relative lowering of vapor pressure is given as 0.0225, we directly get: \[ X_B = 0.0225 \]