HW # 2—THERMO II—CHEN 354—Fall 08
Due Wednesday, September 10, 2008
Problem 1. For a separations process it is necessary to determine the VLE compositions
of a mixture of ethyl bromide and n-heptane at 30oC. At this temperature the vapor
pressure of pure ethyl bromide is 0.7569 bar, and the vapor pressure of pure n-heptane is
0.0773 bar. Calculate the bubble pressure and the composition of the vapor in equilibrium
with a liquid containing 47.23 mol% ethyl bromide assuming ideal solution behavior.
Compare the calculated pressure to the experimental value of 0.4537 bar.
Problem 2. Consider a mixture of 50% mol n-pentane and 50% mol n-butane at 14 bar.
(a) What is the dew point temperature? What is the composition of the first drop of
liquid?
(b) At what temperature is the vapor completely condensed if the pressure is maintained
at 14 bar? What is the composition of the last bubble of vapor?
Problem 3. A 50 mol% of propane (1) and n-butane(2) enters an isothermal flash drum
at 37oC. If the flash drum is maintained at 0.6 MPa, what fraction of the feed exits as
liquid? What are the compositions of the phases exiting the flash drum?
Recommended additional problems: 10.17, 10.18, 10.19, 10.20. (These problems will
not be graded and you don’t need to include the solution in your HW, just do them for
practice).