7. Benzene and toluene form nearly ideal solutions. At

20° C, the vapour pressure of benzene is 75 torr and that of toluene is 22 torr. The partial vapour pressure of benzene at 20° C, for a solution containing  78 g of benzene and 46 g of toluene in torr is

a. 50

b. 25

c. 37.5

d. 53.5

Ans. a