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Engineering LibreTexts

5.6: Action Item

Action Item

Answer the following problems, and submit your answers to the drop box in ANGEL that has been created for this module.

Please note:

  • Your answers must be submitted in the form of a Microsoft Word document.
  • Include your Penn State Access Account user ID in the name of your file (for example, "module2_abc123.doc").
  • The due date for this assignment will be sent to the class by e-mail in ANGEL.
  • Your grade for the assignment will appear in the drop box approximately one week after the due date.
  • You can access the drop box for this module in ANGEL by clicking on the Lessons tab, and then locating the drop box on the list that appears.


Problem Set

  1. Figure 5.2 shows the P-T phase envelopes for eight binary mixtures of Methane and Ethane at eight different compositions. The data was experimentally generated at IGT (Institute of Gas Technology) and presented in the Research Bulletin No. 22. The vapor pressure curves of Methane and Ethane bound the phase envelopes of the eight binary mixtures of Methane and Ethane at different proportions. From left to right, these proportions (molar compositions) are:


Mixture 1 97.50% CH4 and   2.50% C2H6 (closest to 100% pure Methane vapor pressure curve)
Mixture 2 92.50% CH4 and   7.50% C2H6
Mixture 3 85.16% CH4 and 14.84% C2H6
Mixture 4 70.00% CH4 and 30.00% C2H6
Mixture 5 50.02% CH4 and 49.98% C2H6
Mixture 6 30.02% CH4 and 69.98% C2H6
Mixture 7 14.98% CH4 and 85.02% C2H6
Mixture 8 5.00% CH4 and 95.00% C2H6 (closest to 100% pure Ethane vapor pressure curve)
  1. Using this phase behavior data, generate the P-x and T-x diagram for Methane/Ethane mixtures at T = – 40 F and P = 500 psia respectively.
  2. If a certain amount of the mixture 40% C1 – 60% C2 is kept in a vessel at 500 psia, determine the temperature at which the vessel has to be subjected if at least 50% of the substance is required to be in the liquid state. How would your answer change if we were now required to have 10% of liquid in the vessel? How would it change if the overall composition is now considered to be 60% C1 and 40%  C2 ?
  3. 10 lbmol of an equimolar C1/C2 mixture is confined inside a vessel at conditions of – 60oF and 500 psia. What is the percentage of liquid inside the vessel? What is the composition of the liquid and vapor at such condition?
  4. What would be the composition of the first bubble that appears in a isothermal expansion of a liquid at – 40oF? At which pressure would this bubble appear? What would be the pressure at which the first droplet appears in a isothermal compression of a vapor at – 40oF? What is the composition of such a droplet?
  5. Can you apply the lever rule to in a ternary diagram? If not, why not? What about a multicomponent system?


  • Prof. Michael Adewumi (The Pennsylvania State University). Some or all of the content of this module was taken from Penn State's College of Earth and Mineral Sciences' OER Initiative.