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

Answer:

$X_{hexane} = 0,653$

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!