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Front. Chem. | doi: 10.3389/fchem.2018.00035

Thermodynamic analysis of chemically reacting mixtures – comparison of first and second order models

  • 1Faculty of Chemistry, Brno University of Technology, Czechia

Recently, a method based on non-equilibrium continuum thermodynamics which derives thermodynamically consistent reaction rate models together with thermodynamic constraints on their parameters was analyzed using a triangular reaction scheme. The scheme was kinetically of the first order. Here, the analysis is further developed for several first and second order schemes to gain a deeper insight into the thermodynamic consistency of rate equations and relationships between chemical thermodynamic and kinetics. It is shown that the thermodynamic constraints on the so-called proper rate coefficient are usually simple sign restrictions consistent with the supposed reaction directions. Constraints on the so-called coupling rate coefficients are more complex and weaker. This means more freedom in kinetic coupling between reaction steps in a scheme, i.e., in the kinetic effects of other reactions on the rate of some reaction in a reacting system. When compared with traditional mass-action rate equations, the method allows a reduction in the number of traditional rate constants to be evaluated from data, i.e., a reduction in the dimensionality of the parameter estimation problem. This is due to identifying relationships between mass-action rate constants (relationships which also include thermodynamic equilibrium constants) which have so far been unknown.

Keywords: Affinity, entropic inequality, independent reactions, Kinetics, rate constants, rate equations, Thermodynamics

Received: 02 Dec 2017; Accepted: 12 Feb 2018.

Edited by:

Ramesh L. Gardas, Indian Institute of Technology Madras, India

Reviewed by:

Evgeni B. Starikov, Independent researcher, Germany
Miguel Rubi, Universitat de Barcelona, Spain  

Copyright: © 2018 Pekař. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

* Correspondence: Prof. Miloslav Pekař, Brno University of Technology, Faculty of Chemistry, Purkyňova 118, Brno, 627 00, Czechia, pekar@fch.vutbr.cz