4) In class, we'll explore liquid-vapor coexistence curves for a mixture of benzene and toluene.
You'll examine this coexistence in depth in this problem.
At 80 °C, the vapor pressure of pure benzene is 760 torr and that of pure toluene is 200 torr.
You may assume that both the liquid solution and gas mixture behave ideally.
a. Calculate the total vapor pressure of the liquid, $P_{tot}$, as a function of $x_T$, the mole fraction
of toluene in the liquid. Plot $P_{tot}$ as a function of $x_T$ at 80 °C.
b. Calculate the composition of the gas phase in equilibrium with the liquid mixture. Plot $P_{tot}$
as a function of $y_T$, the mole fraction toluene in the gas phase at 80 °C.
c. Look up the enthalpies of vaporization of pure toluene and pure benzene. Use this data in
conjunction with the Clausius-Clapeyron equation to plot the boiling point of the solution
as a function of the solution composition (i.e. plot the temperature at which the total
solution pressure, $P_{tot}$, reaches atmospheric pressure, 760 torr, as a function of $x_T$).
d. Add to the graph in part (c) a curve showing the boiling point of the solution as a function
of the composition of the vapor evolved from the solution (i.e. the temperature at which
$P_{tot}$ = 760 torr vs. $y_T$).
