Question

A solution contains a mixture of pentane and hexane at room temperature. The solution has a vapor pressure of 246 torr . Pure pentane and hexane have vapor pressures of 425 torr and 151 torr, respectively, at room temperature.

a. What is the mole fraction of hexane? (Assume ideal behavior.)

Answer 1

`X_(hexane) = 0,653`

Step-by-step explanation:

The pressure of the solution is:

`P_(solution) = P^0_(hexane)X_(hexane) + P^0_(pentane)X_(pentane)` (1)

`246torr = 151X_(hexane) + 425X_(pentane)` (1)

Where X is mole fraction of each compound. Also, you can write:

`1 = X_(hexane) + X_(pentane)` (2)

Replacing (2) in (1):

`246torr = 151X_(hexane) + 425(1-X_(hexane))`

-179 =
`-274X_(hexane)`

`X_(hexane) = 0,653`

I hope it helps!