Evaluating Volumetric and Other Thermodynamic Properties by Means of Cubic Equations of State©
Baudilio Coto
Department of Chemical and Environmental Technology
ESCET, Rey Juan Carlos University
C/ Tulipan
Móstoles ( Madrid ) 28933
mail to: baudilio.coto@urjc.es

Immaculada Suárez
Department of Chemical and Environmental Technology
ESCET, Rey Juan Carlos University
Móstoles ( Madrid ) 28933


The use of equations of state to evaluate volumetric properties is straightforward for students, at least when the ideal gas equation of state is used. The application of a more complicated equation of state, as a cubic equation, is a little more difficult, specially for the determination of volume. In addition, the use of such equations to determine some other thermodynamic properties results extremely complex for students both from the numerical and theoretical point of view.

The use of Maple to solve involved equations, to manage obtained functions and to display functional dependencies allows students both to obtain required numerical values and to understand the meaning of the calculations.

This work is related with the evaluation of non idealities from several points of view. The Maple sheet allows to determine volumetric properties and compare values obtained from the ideal gas and the Soave (SRK) equations of state. Several aspects of the calculation as the effect of pressure, the lowest available volume, the number of roots, and the relation between volume and compresibility factor are analyzed.

Additional thermodynamic properties are considered. Fugacity coefficient and residual enthalpy are determined from well known thermodynamic relationships and the SRK equation of state. Deviations from ideality are analyzed in terms of all the functions determined.

Editor's Commentary
Audiences: Upper-Division Undergraduate
Pedagogies: Computer-Based Learning
Domains: Physical Chemistry
Topics: Gases, Mathematics / Symbolic Mathematics, Thermodynamics
File NameDescriptionSoftware TypeSoftware Version
CubicEquationsOfState.mw JCE Maple Computational Document (requires Maple 10 or higher). Maple 10
CubicEquationsOfState.pdf Read-Only Document
JCE JCE Subscribers only: name and password or institutional IP number access required.
Suárez, I.; Coto, B. J. Chem. Educ. 2008, 85, 1707.
Comments to: Baudilio Coto at baudilio.coto@urjc.es
©Copyright 2008 by the Division of Chemical Education, Inc., American Chemical Society. All rights reserved. For classroom use by teachers, one copy per student in the class may be made free of charge. Write to JCE Online, jceonline@chem.wisc.edu, for permission to place a document, free of charge, on a class Intranet.