The vapour pressure of pure benzene and toluene are 160 and 60 torr respectively. The mole fraction of toluene in vapour phase in contact with equimolar solution of benzene and toluene is

Options

A. 0.5
B. 0.16
C. 0.27
D. 0.73

Answer

C

Explanation

For equimolar solution, let us take
`x_A=x_B = 0.5`
`P_("benzene") = 160 xx 0.5 = 80` torr,
`P_("toluene") = 60 xx 0.5 = 30` torr
`P_("total") = 80 + 30 = 110` torr
Mole fraction of toluene in vapour phase
`("Partial vapour pressure of toluene")/("Total vapour pressure")=30/110 = 0.27`