Question

two liquids A and B have vapour pressure in the ratio 2:3 at a certain temperature .Assuming that A and B forms an ideal solution and ratio of mole fraction of A and B in the vapour phase is 1:3,then the mole fraction of A in the solution at the same temperature is

Answer 1

$$\begin{gathered} Totalvapourpressure=2+3=5 \\ MolefractionofA=\frac{1}{4}andmolefractionofB=\frac{3}{4}(molesareintheratio1:3) \\ {p}_A=X_A\times P_{Tot} \\ =\frac{1}{4}\times 5=1.25 \\ {p}_B=X_B\times P_{Tot} \\ =\frac{3}{4}\times 5=3.75 \\ ThusthemolefractionofA \\ \frac{P_A}{P_B}\alpha X_A \\ {X}_A=\frac{1.25}{3.75}=\frac{1}{3} \end{gathered}$$