The vapour pressure of two liquids X and Y are 80 and 60 torr respectively. The total vapour pressure of the ideal solution obtained by mixing 3 moles of X and 2 moles of Ywould be

Options

A. 68 Torr
B. 140 Torr
C. 48 Torr
D. 72 Torr

Answer

D

Explanation

According to given information
`p _(X) =80` Torr
`p _(Y) =60` Torr
`n _(X)=3` moles
`n_(X) =2` moles
`n _(Y)=2` moles
mole fraction of `X (x_(X))=(n _(X))/(n _(X)+ n_(Y))=(3)/(3+2) =3/5`
mole fraction of `Y (x _(Y))=(n_(X))/(n_(X)+ n _(Y)) =(2)/(3+2) =2/5`
Total Pressure, `P = p_(x) x _(X) + p_(Y) x _(Y)`
`=3/5x 80 +2/5 xx 60 =40+24=72.` Torr.