The vapour pressure of water at room temperature is 23.8 mm Hg. The vapour pressure of an aqueous solution of sucrose with mole fraction 0.1 is equal to :

The correct option is C. $21.42$ mm Hg

$P_o$ (Vapour pressure of water) = 23.8 $mmHg$

$P_s$ (Vapour pressure of sucrose) = ?
on solving as attached in the image we get

$P_s$ (Vapour pressure of sucrose) = 21.42 $mmHg$

$\frac{P_o-P_s}{P_o}=0.1$ (mole fraction)

$\frac{23.8-P_s}{23.8}=0.1$

$23.8-P_s=2.38$ or $P_s=21.42$ mm of Hg