The vapour pressure of two liquid P and Q are 80 torr and 60 torr respectively. The total vapour pressure obtained by mixing `3` moles of P and 2 mole of Q would be

Options

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

Answer

D

Explanation

Mole fraction of `P=(3)/(3+2)=(3)/(5)`
Mole fraction of `Q=(2)/(3+2)=(2)/(5)`
Hence, total vapour pressure = Mole fraction of `P xx` vapour pressure of P + mole fraction of `Q xx` vapour pressure of `Q =((3)/(5)xx80+(2)/(5)xx60)=48+24=72` torr