At 25 $\circ$ C, the vapor pressure of pure water is 25.756 mm Hg. What is the vapor pressure of water in a 0.500 m solution of sodium chloride?

Question

Quizplus · Accepted Answer

The vapor pressure of water in a 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 times the mole fraction of the solvent in the solution. Sodium chloride dissociates into two ions (Na+ and Cl-) in solution, so a 0.500 m solution of NaCl actually results in a 1.0 m total particle concentration. This decreases the mole fraction of water, thus lowering its vapor pressure slightly from the pure solvent's vapor pressure. The correct answer is the one that shows a slight decrease from the pure water vapor pressure of 25.756 mm Hg, which is 25.52 mm Hg.

At 25 ∘\circ∘ C, the Vapor Pressure of Pure Water Is 25

At 25^$\circ$C, the Vapor Pressure of Pure Water Is 25