Answer to Question #315900 in Chemistry for grey tyrant

Question

1. The vapor pressure of pure water at 110oC is 1070 torr. A solution of ethylene glycol and water has a vapor pressure of 1.10 atm at the same temperature. What is the mole fraction of ethylene glycol in the solution?

Answer 1

Solution:

solvent = water

solute = ethylene glycol

Convert atm to torr:

1 atm = 760 torr

Therefore,

(1.10 atm) × (760 torr / 1 atm) = 836 torr

P_solution = 836 torr

According to Raoult's law, the addition of non-volatile solute to a pure solvent decreases the vapor pressure of the solvent.

The relative lowering of vapor pressure is calculated by the expression shown below:

χ_solute = (P°_solvent − P_solution) / P°_solvent

where,

P_solution is the vapor pressure of the solution

P°_solvent is the vapor pressure of the pure solvent

χ_solute is the mole fraction of the solute

P_solution = 836 torr

P°_solvent = 1070 torr

Therefore,

χ_solute = (1070 torr − 836 torr) / (1070 torr) = 0.219

χ_solute = 0.219

Answer: The mole fraction of ethylene glycol in the solution is 0.219