Question

Biphenyl, C12H10, is a nonvolatile, nonionizing solute that is soluble in benzene, C6H6. At 25 °C, the vapor pressure of pure benzene is 100.84 torr. What is the vapor pressure of a solution made from dissolving 11.1 g of biphenyl in 27.2 g of benzene?

Answer 1

moles of benzene = 27.2 g/78.11 g/mol = 0.35 mols

moles of biphenyl = 11.1 g/154.21 g/mol = 0.072 mols

moles fraction of benzene = 0.35/(0.35 + 0.072) = 0.83

Vapor pressure of solution = vapor pressure of benzene x mole fraction of benzene

                                           = 100.84 x 0.83 = 83.70 torr