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On finding the rate constants of linear and nonlinear systems
Author(s) -
Liddell G. F.,
Evans A. B.,
Buckingham D. A.
Publication year - 1990
Publication title -
international journal of chemical kinetics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.341
H-Index - 68
eISSN - 1097-4601
pISSN - 0538-8066
DOI - 10.1002/kin.550220906
Subject(s) - nonlinear system , reaction rate constant , ordinary differential equation , constant (computer programming) , linear differential equation , differential equation , mathematics , reaction rate , chemistry , mathematical analysis , physics , kinetics , quantum mechanics , programming language , catalysis , biochemistry , computer science
In lowest approximation, a certain chemical reaction is described by a system of first‐order linear differential equations with unknown constant coefficients. One can therefore write down an expression for the state of the system at time t , and from this find the endpoint of the reaction in terms of the initial state and the rate constants. The relative values of some rate constants can then be estimated from experimental data. A better approximation in which the differential equations are nonlinear is also considered, and it turns out that because of symmetry in the reaction, the relationship between the final state and the ratios of the rate constants is unchanged. Although the differential equations now appear much less tractable, the problem of relating the rate constants to the endpoint of the reaction can be formulated and solved in terms of probabilities. The results illustrate an important property of reaction schemes in which some of the steps are reversible. More generally, this is a property of differential equations: provided that they continue to satisfy certain linear constraints, the parameters of a linear system of ordinary differential equations can vary without affecting the asymptotic solution.