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 torr. The MW of lactose is 342.3 g/mol.
A) 169.4
B) 1.670
C) 92.7
D) 94.1
E) 116.3

Question

Quizplus · Accepted Answer

The vapor pressure of the solution can be calculated using Raoult's Law: P_solution = X_solvent * P_pure solvent. First, calculate the moles of lactose (30.00 g / 342.3 g/mol) and water (110.0 g / 18.015 g/mol). Then, find the mole fraction of water (X_solvent). Finally, multiply the mole fraction by the vapor pressure of pure water (118 torr) to find the vapor pressure of the solution.

A Solution Is Prepared by Adding 30