Question

The vapor pressure of benzene (C6H6) is 73.0 mm Hg at 25 °C. What is the vapor pressure of a solution consisting of 179 g of benzene and 0.217 mol of a nonvolatile nonelectrolyte?

Answer 1

Answer:

Vapor pressure of solution is 66.7 mmHg

Explanation:

Colligative property about vapor pressure lowering. That's we must use to solve this problem.

Formula is: ΔP = P° . Xm

P° is Vapor pressure of pure solvent

ΔP = P° - P' (vapor pressure of solution)

Xm = mole fraction of solute (mol of solute / total moles)

Let's determine the total moles, firstly.

Total moles = moles of solute + moles of solvent

Moles of solute → 0.217 mol

Moles of solvent → 179 g / molar mass of benzene

179 g / 78 g/mol = 2.29  mol

2.29 mol + 0.217 mol = 2.507 moles

Xm for solute = 0.217 mol / 2.507 mol = 0.0865

Let's replace the data in the formula:

73 mmHg - P' = 73 mmHg  . 0.0865

P' = - (73 mmHg  . 0.0865  - 73mmHg)

P' = 66.7 mmHg