The vapour pressure of two liquids 'P' and 'Q' are 80 and 60 torr respectively. The total vapour pressure of solution obtained by mixing 3 mole of P and 2 mol of Q would be

Options

A. 72 torr
B. 140 torr
C. 68 torr
D. 20 torr

Answer

A

Explanation

Given `V.P_p = 80` torr
`V.P_Q = 60` torr
`P_("total") = V.P_P xx x_P + V.P_Q xx x_Q`
`=[80 xx 3/5 + 60 xx 2/5] = 16 xx 3 + 12 xx2`
`P_("total") = 48 + 24 = 72` torr