Question

What is the mole fraction of benzene in the solution that has a vapor pressure of 38 torr at 20 ∘C? Express your answer using two significant figures.

Answer 1

The question is incomplete, here is the complete question:

At 20°C the vapor pressure of benzene
`(C_6H_6)` is 75 torr, and that of toluene
`(C_7H_8)` is 22 torr. Assume that benzene and toluene form an ideal solution.

What is the mole fraction of benzene in the solution that has a vapor pressure of 38 torr at 20°C? Express your answer using two significant figures.

Answer: The mole fraction of benzene is 0.302

Step-by-step explanation:

Let the mole fraction of benzene be 'x' and that of toluene is '1-x'

To calculate the total pressure of the mixture of the gases, we use the equation given by Raoult's law, which is:

`p_T=\sum_(i=1)^n(\chi_(i)* p_i)`

We are given:

Vapor pressure of benzene = 75 torr

Vapor pressure of toluene = 22 torr

Vapor pressure of solution = 38 torr

Putting values in above equation, we get:

`38=[(75* x)+(22* (1-x))]\\\\x=0.30`

Hence, the mole fraction of benzene is 0.30