A solution is prepared by adding 30.00 g of lactose (milk sugar)to 110.0 g of water at 55°C. The partial pressure of water above the solution is __________ torr. The vapor pressure of pure water at 55°C is 118.0 torr. The MW of lactose is 342.3 g/mol.
A)1.670
B)94.1
C)169.4
D)116.3
E)92.7

Question

Quizplus · Accepted Answer

The partial pressure of water above the solution can be calculated using Raoult's Law: P_solution = X_solvent * P_pure. First, calculate the mole fraction of water (solvent). Moles of lactose = 30.00 g / 342.3 g/mol = 0.0877 mol. Moles of water = 110.0 g / 18.015 g/mol = 6.107 mol. Mole fraction of water = 6.107 / (6.107 + 0.0877) = 0.986. P_solution = 0.986 * 118.0 torr = 116.3 torr.

A Solution Is Prepared by Adding 30