# Problem: Glycerin, C3H8O3, is a nonvolatile liquid. What is the vapor pressure of a solution made by adding 164 g glycerin to 338 mL H2O at 39.8°C? The vapor pressure of pure water at 39.8°C is 54.74 torr and its density is 0.992 g/cm3.

###### FREE Expert Solution

Vapor Pressure Lowering is a colligative property which describes the decrease in vapor pressure of a solution when a solute is added to a solution.

The formula for vapor pressure lowering is:

$\overline{){{\mathbf{P}}}_{{\mathbf{solution}}}{\mathbf{=}}{{\mathbf{\chi }}}_{{\mathbf{solvent}}}{\mathbf{·}}{\mathbf{P}}{{\mathbf{°}}}_{{\mathbf{solvent}}}}$

Where:

Psolution is the vapor pressure of the solution

solvent is the vapor pressure of pure solvent

Xsolvent is the mole fraction of the solvent

Solve for the mole fraction of the solvent:

$\overline{){{\mathbf{\chi }}}_{{\mathbf{solvent}}}{\mathbf{=}}\frac{{\mathbf{mol}}_{\mathbf{solvent}}}{\mathbf{\iota }\mathbf{·}{\mathbf{mol}}_{\mathbf{solute}}\mathbf{+}{\mathbf{mol}}_{\mathbf{solvent}}}}$

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###### Problem Details

Glycerin, C3H8O3, is a nonvolatile liquid. What is the vapor pressure of a solution made by adding 164 g glycerin to 338 mL H2O at 39.8°C? The vapor pressure of pure water at 39.8°C is 54.74 torr and its density is 0.992 g/cm3.