Thermodynamic Branch in the Chemical System Response to External Impact

TL;DR

This paper investigates the thermodynamic response of chemical systems to external forces, revealing linear relationships between the system's shift rate and the applied force, and introduces a quantitative framework for analyzing such deviations.

Contribution

It introduces a detailed thermodynamic model describing chemical system deviations from equilibrium under external impact, emphasizing the role of the thermodynamic equivalent of transformation.

Findings

The full thermodynamic branch forms an S-shaped curve with asymptotic ends.

The slope of the steepest parts is proportional to the external force and the thermodynamic equivalent.

The linearity holds for arbitrary stoichiometric coefficients in chemical reactions.

Abstract

The paper gives an account of a detailed investigation of the thermodynamic branch as a path of the chemical system deviation from its isolated thermodynamic equilibrium under an external impact. For a combination of direct and reverse reactions in the same chemical system, full thermodynamic branch is presented by an S-shaped curve, whose ends asymptotically achieve appropriate initial states, which, in turn, are logistic ends of the opposite reactions. The slope tangents of the steepest parts of the curves, the areas of the maximum rate of the shift growth vs. the external thermodynamic force, occurred to be directly proportional to the force and, simultaneously, linearly proportional to the thermodynamic equivalent of chemical reaction, which is the ratio between the amount in moles of any reaction participant, transformed in an isolated system, along the reaction way from its initial state to thermodynamic equilibrium, to its stoichiometric coefficient. The found linearity is valid for arbitrary combination of the stoichiometric coefficients in a reaction of compound synthesis from chemical elements like aA+bB=AaBb, and confirms the exclusive role of the thermodynamic equivalent of transformation as the chemical system characteristic of robustness and irreversibility. Results of this work allow for quantitative evaluation of the chemical system shift from thermodynamic equilibrium along thermodynamic branch and its rate vs. the shifting force. Such an investigation became possible due to the development of discrete thermodynamics of chemical equilibria.