At `25^(@)C`, the vapour pressure of pure liquid `A ( mol wt. =40)` is `100 t o r r` , while that of pure liquid `B` is 40 torr, `( mol. Wt. =80 )`. The vapour pressure at `25^(@)C` of a solution containing `20g` of each A and B is :

Options

A. 80 torr
B. `59.8 t o rr`
C. `68 t o rr`
D. 48 torr

Answer

1

Explanation

Moles of A `=(20)/(40)rArr0.5,`
Moles of B `=(20)/(80)rArr0.25,`
`X_(A)=(0.5)/(0.5+0.25)=0.67,X_(B)=0.33`
`P_("total")=P_(A)^(@)X_(A)+P_(B)^(@)X_(B)`
`rArr" "100xx0.67+40xx0.33rArr80`torr