Mole fraction of the toluene in the vapour phase which is in equilibrium with a solution of benzene
`(p ^(@) = 120` Torr) and toluene
`(p ^(@) = 80` Torr) having 2. 0 moles of each, is

Options

A. `0. 50`
B. `0. 25`
C. `0. 60`
D. `0. 40`

Answer

D

Explanation

Mole fraction on tolene vapour
`= ( p _(T) ^(@) X _(T))/( P _(T) ^(@) X _(T) + p _(B) X _(B))`
` = X _(T) ` Mole fraction of benzene `= 2//4 = 0.5`
`P _(T) ^(@) =` Vapour pressure of pure toluene = 80 mm
`p _(T) ^(@) = ` Vapour pressure of benzene = 120 mm
`= ( 80 xx 4)/( 5. 80 + 120 xx 0. 5) = 0. 40`