The theory of response reactions (RERs) or response equilibria was elaborated for the

thermodynamic Thermodynamics is a branch of physics that deals with heat, work, and temperature, and their relation to energy, entropy, and the physical properties of matter and radiation. The behavior of these quantities is governed by the four laws of ther ...

systems in which more than one equilibrium is established simultaneously. It is based on detailed analysis of the

Hessian determinant In mathematics, the Hessian matrix or Hessian is a square matrix of second-order partial derivatives of a scalar-valued function, or scalar field. It describes the local curvature of a function of many variables. The Hessian matrix was developed ...

. The theory derives the sensitivity coefficient as the sum of the contributions of individual RERs. Thus all phenomena which are in apparent contradiction to the

Le Chatelier principle Le Chatelier's principle (pronounced or ), also called Chatelier's principle (or the Equilibrium Law), is a principle of chemistry used to predict the effect of a change in conditions on chemical equilibria. The principle is named after French ...

could be interpreted. With the help of RERs the equilibrium coupling was defined. RERs could be derived based either on the species, or on the stoichiometrically independent reactions of a parallel system. The set of RERs is unambiguous in a given system; and the number of them (M) is

S \choose C+1

, where S denotes the number of species and C refers to the number of components. In the case of three-component systems, RERs can be visualized on a triangle diagram.

References

Thermodynamics {{Thermodynamics-stub