1. Ethanol and propanol form an ideal solution at 36 °C. The vapor pressure of pure ethanol and
pure propanol is 108 mmHg and 40.0 mmHg, respectively.
a. Prepare a diagram showing the vapor pressure of the components and the total vapor
pressure as a function of the mole fraction. Fit a trend line on the total pressure line.
b. Using the equation for the total pressure trend line determine the composition of the
solution, if the total vapor pressure is 72 mmHg. Mark this point on the graph.
c. What is the composition of the vapor over the liquid?
d. What would be the total vapor pressure if the mole fraction of propanol was 0.600?
e. Include the graph with your work. Show calculations, equations, explanations as applicable
for full credit!
Equation for the vapor pressure line:
y =
Composition of the liquid phase if the vapor pressure is
72 mmHg
Composition of the vapor phase if the vapor pressure is
72 mmHg
$x_{propanol}$ =
$x_{ethanol}$ =
$x^v_{propanol}$ =
$x^v_{ethanol}$ =
Total vapor pressure if $x_{propanol}$ = 0.600:
Hint: Prepare a table in Excel as shown below. Use values for the range 0-1 with 0.1 step for the
x(PrOH) column. Plot the pressure columns as a function of the x(PrOH) column (scatter plot, no
markers). Add a trendline with equation to the p(total) line.
x(PrOH) x(EtOH) p(PrOH) p(EtOH) p(total)