Question

The vapour pressure of solvent decreased by 10 mm of mercury when a non-volatile solute was added to solvent. The mole fraction of the solute in the solution is 0.2. What would be the mole fraction of the solvent if the decrease in the vapour pressure is to be 20 mm of mercury?

• A. 0.8
• B. 0.6
• C. 0.4
• D. 0.2

Answer 1

The correct option is B 0.6

$\frac{10}{P_s}=x_{solute}=0.2$
$P_s=50$
$\frac{20}{50}=x_{solute}\Rightarrow x_{solute}=0.4$
Mole fraction of solvent = 0.6