The vapor pressure of pure water at 110 °C is 1070 torr. A solution of ethylene glycol and water has a vapor pressure of 1.00 atm at 110 °C. Assuming that Raoult's law is obeyed, what is the mole fraction of ethylene glycol in the solution? g

0.291

Explanation:

Given data

Vapor pressure of the pure solvent (Psolvent) : 1.41 atm

1070 torr * (1 atm / 760 torr) = 1.41 atm

Vapor pressure of the solvent above the solution (Psolution) : 1.00 atm

According to Raoult's law, the vapor pressure of a solvent above a solution is equal to the vapor pressure of the pure solvent at the same temperature scaled by the mole fraction of the solvent present.

Psolution = Psolvent * Χsolvent

Χsolvent = Psolution/Psolvent

Χsolvent = 1.00 atm/1.41 atm

Χsolvent = 0.709

The sum of the mole fraction of the solvent (water) and the solute (ethylene glycol) is 1.

Χsolvent + Χsolute = 1

Χsolute = 1 - Χsolvent = 1 - 0.709

Χsolute = 0.291