The Colligative Properties Video Lessons

Concept:

Problem: The density of a 0.438 M solution of potassium chromate (K2 CrO4) at 298 K is 1.063 g/mL.Calculate the vapor pressure of water above the solution. The vapor pressure of pure water at this temperature is 0.0313 atm. Assume complete dissociation.

FREE Expert Solution

We are asked to calculate the vapor pressure of water above a solution of 0.438 M K2CrOat 298K.

When a solute is added to the solvent, some of the solute molecules occupy the space near the surface of the liquid.

When a solute is dissolved in a solvent, the number of solvent molecules near the surface decreases, and the vapor pressure of the solvent decreases.

Recall Raoult’s equation where it shows that the vapor pressure of a solution is equal to the mole fraction of the solvent times the vapor pressure of the pure liquid.

Where:

P=vapor pressure of the solvent above a solution

Po = vapor pressure of pure solvent

χ=  mole fraction of solvent

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Problem Details

The density of a 0.438 M solution of potassium chromate (K2 CrO4) at 298 K is 1.063 g/mL.

Calculate the vapor pressure of water above the solution. The vapor pressure of pure water at this temperature is 0.0313 atm. Assume complete dissociation.