Question

Biphenyl, C12H10,C12H10, is a nonvolatile, nonionizing solute that is soluble in benzene, C6H6.C6H6. At 25 ∘C,25 ∘C, the vapor pressure of pure benzene is 100.84 Torr. What is the vapor pressure of a solution made from dissolving 19.2 g19.2 g of biphenyl in 33.7 g33.7 g of benzene?

Answer 1

Answer:

Vapour pressure of solution is 78.151 torr

Explanation:

Molar mass of biphenyl = 154.21 g

Molar mass of benzene = 78.11 g

19.2 g biphenyl = (19.2/154.21) moles of biphenyl = 0.125 moles of biphenyl

33.7 g of benzene = (33.7/78.11) moles of benzene = 0.431 moles of benzene

Total number of moles = (0.125+0.431) moles = 0.556 moles

Mole fraction of benzene in solution = (0.431/0.556) = 0.775

According to Roults law, vapour pressure of solution made from non-volatile solute = $(mole fraction of solvent in solution)\times (vapour pressure of pure solvent)$

Here solute is biphenyl and solvent is benzene

So, vapour pressure of solution = $(0.775\times 100.84)torr$ = 78.151 torr