Chemistry - Liquid Solution Question with Solution | TestHub

From Raoult's law for a solution of two volatile liquids, the total vapour pressure is given by:

$P_{\text{total}}=P_A^0{x}_A+P_B^0{x}_B$

Given:
$x_B=0.4$
$P_B^0=900\text{ mm Hg}$
$P_{\text{total}}=600\text{ mm Hg}$

Since the sum of mole fractions is $1$, we have:
$x_A=1-x_B=1-0.4=0.6$

Substituting the values into the equation:
$600=P_A^0(0.6)+900(0.4)$

$600=P_A^0(0.6)+360$

$P_A^0(0.6)=600-360$

$P_A^0(0.6)=240$

$P_A^0=\frac{240}{0.6}=400\text{ mm Hg}$

Answer: 400 mm Hg