Question

Given that the vapor pressure of pure TOLUENE at 32°C is 41 torr, the vapor pressure in torr of a solution of 0.39 mol cholesterol in 5.4 mol toluene at 32°C is what

Answer 1

The vapor pressure of the solution is 38 Torr.

Explanation:

This problem can be solved using Raoult's law. This law states that the vapor pressure of a mixed solution is directly proportional to the partial pressure of the pure solvent and the mole fraction of the solvent in the solution.

So, here the solvent is toulene and the solute is cholesterol. As the solute is not completely mixed in the solvent , the vapor pressure of the solution will depend on the vapor pressure and mole fraction of the solvent.

The vapor pressure of the solvent i.e., toulene is given as 41 torr.

The total mole of the solution is 0.39+5.4, which will be equal to 5.79 mole.

So in 5.79 moles of the solution, toulene has only 5.4 mole in it.

Then the mole fraction will be $\frac{5.4}{5.79} = 0.933$

Then, the vapor pressure of the solution = Mole fraction × Vapor pressure of solvent

$Vapor\ pressure\ of\ solution = 0.933 \times 41 = 38\ Torr$

Thus, the vapor pressure of the solution is 38 Torr.