Exercise 6 | Colligative Properties of Solutions

The vapor pressure of pure water at 65oC is 412 torr.

What is the vapor pressure at 65oC of a solution prepared from 100 mL of water (density 1.00 g/mL) and 120 g of diglyme, C6H14O3, a nonvolatile substance?

Raoult’s Law:
 

Pwater = xwater P0water

Pwater = vapor pressure of the water in the solution

xwater = mole fraction of water in the solution

P0water = vapor pressure of the pure water


xwater = nwaternwater + ndiglyme

nwater = mwaterMwater = 10018.0  = 5.55 mol

ndiglyme = mdiglymeMdiglyme = 120134.17 = 0.894 mol

xwater = 5.556.45 = 0.861

 

Pwater = xwater P0water = 0.861 x 412 = 355 torr