On the Distinction between Reaction Fluxes and Phenomenological Rate Constant

Abstract

The physical interpretation of the phenomenological rate constants of chemical kinetics is examined. For perfect gas systems, the traditional view of the rate constants for elementary reactions as one-way reaction fluxes is compared with a more recent interpretation (3) in terms of more complicated functions; it is concluded that, for real systems, the former view is a special case of the latter, while for systems in which the phenomenological rate equation is exact, the rate constants are shown to be one-way fluxes.In any given system, the applicability of the special interpretation is a function of the detailed nature of the transport matrix, which is generally unknown; practical implications of these ideas are presented. For systems other than perfect gases, the problem is complicated by the absence of well-defined molecular states; however, it is suggested that the flux interpretation is the most reasonable.