A sample of 2.00 g of the non-volatile compound urea, CO(NH₂) ₂ (molar mass = 60 g/mol) , is dissolved in 20.0 grams of water. What is the vapor pressure of water above this solution?
The vapor pressure of pure water at the temperature of the experiment is 0.150 atm.

Question

Quizplus · Accepted Answer

The vapor pressure of the solution can be calculated using Raoult's Law, which states that the vapor pressure of a solvent in a solution is equal to the vapor pressure of the pure solvent multiplied by the mole fraction of the solvent in the solution. The mole fraction of water in the solution can be calculated by dividing the moles of water by the total moles of both water and urea. Given that the molar mass of urea is 60 g/mol, 2.00 g of urea is 0.0333 moles. The molar mass of water is approximately 18 g/mol, so 20.0 grams of water is approximately 1.11 moles. The mole fraction of water is therefore 1.11 / (1.11 + 0.0333) ≈ 0.971. Multiplying this by the vapor pressure of pure water (0.150 atm) gives a vapor pressure of the solution of approximately 0.146 atm.

A Sample of 2