Vapor pressure and mole fraction

Question

An equimolar liquid mixture of water and ethanol is in equilibrium with its vapor.

(i) Find the total vapor pressure

(ii) Find the mole fraction of water in vapor.

P(water)=24mmHg

P(ethanol)=45mmHg

Answer 1

Equmolar mixture = mole fraction of each is 0.5

Partial pressure of water vapor = 0.5 x 24 mm Hg = 12 mm Hg

Partial pressure of ethanol vapor = 0.5 x 45 mm Hg = 22.5 mm Hg

(i) Total vapor pressure = 12 mm Hg + 22.5 mm Hg = 34.5 mm Hg = 35 mm Hg

(ii) Mole fraction of water in the vapor = 12 mm Hg / 35 mm Hg = 0.34