Problem: At 40°C, heptane has a vapor pressure of about 91.5 torr and octane has a vapor pressure of about 31.2 torr. Assuming ideal behavior, what is the vapor pressure of a solution that contains twice as many moles of heptane as octane?A. 81.8 torrB. 51.3 torrC. 10.4 torrD. 71.4 torrE. 61.0 torr

🤓 Based on our data, we think this question is relevant for Professor Schurmeier's class at UCSD.

FREE Expert Solution

We’re being asked to determine the vapor pressure of a solution contains twice as many moles of heptane as octane?


Recall that the vapor pressure of a solution can be given by Raoult’s Law.

The given solutions are composed of heptane and octane, which are both volatile. For a solution with volatile solute and solvent, Raoult’s Law is given as:


Psolution = (P°heptaneXheptane) + (P°octaneXoctane)


where P˚ = vapor pressure of pure component and χ = mole fraction of component. Recall that the mole fractions in a solution add up to 1. Since the solution is composed of heptane and octane, this means:


Xoctane = 1 - Xhexane


View Complete Written Solution
Problem Details

At 40°C, heptane has a vapor pressure of about 91.5 torr and octane has a vapor pressure of about 31.2 torr. Assuming ideal behavior, what is the vapor pressure of a solution that contains twice as many moles of heptane as octane?

A. 81.8 torr

B. 51.3 torr

C. 10.4 torr

D. 71.4 torr

E. 61.0 torr