At 60° C, vapour pressure of methanol and water are 84.562 kPa and 19.953 kPa respectively. An aqueous solution of methanol at 60° C exerts a pressure of 39.223 kPa; the liquid phase and vapour phase mole fractions of methanol are 0.1686 and 0.5714 respectively. Activity co-efficient of methanol is

A. 1.572

B. 1.9398

C. 3.389

D. 4.238

Answer: Option A

Solution(By Examveda Team)

Given $${x_i} = 0.1686$$   and $${y_i} = 0.5714,\,P{\text{ }} = {\text{ }}39.233{\text{ }}Kpa$$       and $${p_{sat}} = 84.562\,Kpa$$
Since activity co-efficient of methanol $$ = \frac{{{y_i}P}}{{{x_i}p_i^{sat}}} = 0.152$$