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ERIC Number: EJ935045
Record Type: Journal
Publication Date: 2010
Pages: 1
Abstractor: As Provided
Reference Count: 0
ISSN: ISSN-0009-2479
Vapor-Liquid Equilibria Using the Gibbs Energy and the Common Tangent Plane Criterion
Olaya, Maria del Mar; Reyes-Labarta, Juan A.; Serrano, Maria Dolores; Marcilla, Antonio
Chemical Engineering Education, v44 n3 p236 Sum 2010
Phase thermodynamics is often perceived as a difficult subject with which many students never become fully comfortable. The Gibbsian geometrical framework can help students to gain a better understanding of phase equilibria. An exercise to interpret the vapor-liquid equilibrium of a binary azeotropic mixture, using the equilibrium condition based on the common tangent plane criterion (the Gibbs stability test), is presented in this paper. From a T-composition phase diagram for the mixture, the temperature is set at different values: above, intermediate to, and below the boiling temperatures of the pure components, to intersect different regions of the system. Students prepare an Excel spreadsheet where the Gibbs energy of mixing of the vapor and liquid mixtures are calculated and represented over the whole range of compositions and then, apply the Gibbs stability test to ascertain the aggregation state of the system and to calculate the VL phase equilibrium compositions. Finally, Matlab is used to generate the 3-D Gibbs energy of mixing surfaces for both phases over the whole range of temperatures which facilitates the geometrical interpretation of the vapor-liquid equilibrium.
Chemical Engineering Education, Chemical Engineering Division of ASEE. P.O. Box 142097, Gainesville, FL 32614. Tel: 352-392-0861; Fax: 352-392-0861; e-mail:; Web site:
Publication Type: Journal Articles; Reports - Descriptive
Education Level: Higher Education
Audience: N/A
Language: English
Sponsor: N/A
Authoring Institution: N/A