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The Chemical Educator

ISSN: 1430-4171 (electronic version)

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Abstract Volume 8 Issue 1 (2003) pp 4-9

Calculation of the Thermodynamics of Mixing of Fluids Using Simple Equations of State

Wayne B. Bosma

Department of Chemistry and Biochemistry, Bradley University, Peoria, Illinois 61625,
Received October 8, 2002. Accepted November 17, 2002

Published online: 16 January 2003

Abstract. The Redlich–Kwong and van der Waals equations of state were used to calculate the enthalpy, entropy, and Gibbs free energy of mixing for the CO2/C2H6 binary system, as a function of composition. Comparison with experimental enthalpies of mixing shows that both of these equations perform well qualitatively, including a representation of phase changes from vapor to liquid at high pressures. The Redlich–Kwong equation provides a better quantitative estimate of the enthalpy of mixing for this system. It is observed that the ideal fluid estimate of the free energy of mixing is fairly accurate at high pressures, largely due to a cancellation of enthalpy and entropy terms in the real gas free energy.

Key Words:  In the Classroom; physical chemistry; thermodynamics; gases; non-ideal

(*) Corresponding author. (E-mail:

Article in PDF format (360 KB) HTML format

Supporting Materials:

Two supporting files, the MathCad documents for both the van der Waals and the Redlich–Kwong calculations are available in one zip file (28 KB zip file) 10.1333/s00897020647a.

Issue date: February 1, 2003

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