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.