You are now a chemical engineer in the process of designing a plant to separate hydrocarbons obtained from crude oil. You need to keep track of the composition of the mixtures you are dealing with, both the vapors and the liquids. Find the mole fraction of benzene at 25°C in the vapor of a solution of benzene in toluene in which one-third of the molecules in the liquid are benzene.

ANTICIPATE Benzene is more volatile than toluene, so you should expect the vapor to be richer in benzene than the liquid is.