Solutions of benzene and toluene obey Raoult's law.The vapor pressures at 20°C are: benzene,76 torr;toluene,21 torr.
-What is the mole fraction of benzene in a benzene-toluene solution whose vapor pressure is 51 torr at 20°C?

Question

Quizplus · Accepted Answer

According to Raoult's law, the vapor pressure of a solution is equal to the mole fraction of each component multiplied by its vapor pressure in its pure state.

Let x be the mole fraction of benzene. Then, the mole fraction of toluene is (1-x).

Using the given vapor pressures, we can set up the following equation:

51 = x(76) + (1-x)(21)

Solving for x gives x = 0.55. Therefore, the mole fraction of benzene in the solution is 0.55.

Thus, the best choice is C.

Solutions of Benzene and Toluene Obey Raoult's Law