Question

If 0.600 mol of a nonvolatile nonelectrolyte are dissolved in 3.70 mol of water, what is the vapor pressure ph2o of the resulting solution? the vapor pressure of pure water is 23.8 torr at 25 ?c .

Answer 1

To get the vapor pressure of the resulting solution, we use the Raoult’s Law:

Psolution = (χsolvent) (P°solvent)

1st: Calculate the mol fraction of the solvent. In this case, water is the solvent.

χsolvent = 3.7 mol / (3.7 mol + 0.6 mol)

χsolvent = 0.86

2nd: Calculate the vapor pressure.

Psolution = (0.86) (23.8 torr)

Psolution = 20.48 torr