Principle of Detailed Balance and the Second Law of Thermodynamics in Chemical Kinetics

Abstract

The principle of detailed balance is shown to be a sufficient condition for the second law of thermodynamics in thermally equilibrated elementary chemical reactions. For an elementary reaction, the principle of detailed balance relates the forward and the reverse rate constants through the reaction equilibrium constant. It is shown that, in addition to the long known thermodynamic inconsistency at chemical equilibrium state, departure from this principle introduces an extra source/sink of entropy in the entropy balance for an elementary chemical reaction. The departure results in the wrong final chemical equilibrium state and, depending on the choice of the reverse rate constants, may lead to negative entropy productions during kinetic transients.