At 25°C the vapour pressure of pure pentane is 511 torr and that of hexane is 150. torr.

Question

What is the mole fraction of pentane in a pentane-hexane solution that has a vapour pressure of 333 torr at 25°C?

Answer 1

ppen = Xpen*P^o_pentane
phex = Xhex*P^o_hexane

(511*Xpen) + (150*Xhex) = 333
(511*Xp) + 150(1-Xp) = 333
Solve for Xpentane and Xhexane.