# Exercise 8 | Colligative Properties of Solutions

What is the vapor pressure of an aqueous solution of D-Glucose-d12 with a molality m = 2.50 mol.kg-1?

Data: Vapor pressure of water = 25.756 mmHg at 25°C

Raoult’s Law:

Pwater = xwater P0water

Pwater = vapor pressure of the aqueous solution

xwater = mole fraction of water in the solution

P0water = vapor pressure of the pure water

xwater + xsolute = 1

xsolute = $\frac{{\mathrm{n}}_{\mathrm{solute}}}{{\mathrm{n}}_{\mathrm{solution}}}$ =  = m x Msolution

xsolute = m (in mol.g-1) x Msolution (in g.mol-1) = 2.50 x 10-3 x 18.0 = 4.50 x 10-2

xwater = 1 - 4.50 x 10-2 = 0.955

Pwater = xwater P0water = 0.955 x 25.756 = 24.6 mmHg