"Published in Newark, California, USA"
The vapor pressures of pure benzene and toluene at 60°C are 385 and 135 Torr, respectively. Calculate (a) the partial pressures of benzene and toluene, (b) the total vapor pressure of the solution, and (c) the mole fraction of toluene in the vapor above a solution with 0.60 mole fraction toluene.
Solution:
In the given problem, if mole fraction of toluene in a solution is
then mole fraction of benzene in a solution is
The sum of the mole fractions of the components in a solution must be equal to 1. In this case, benzene and toluene are the components in a solution.
The vapor pressures of pure benzene and toluene at 60°C are
(a) By Raoult's Law, we can calculate the partial pressures of benzene and toluene in the vapor.
Partial Pressure of Benzene:
Partial Pressure of Toluene:
(b) The total vapor pressure of the solution is
(c) Since we know already the partial pressures of benzene and toluene as well as the total vapor pressure of the solution, therefore, the mole fraction of toluene in the vapor is
