Considerations on the single-step kinetics approximation

Mechanism of the processes in condensed phase are very often unknown or too complicated to be characterised by a simple kinetic model. They tend to occur in multiple steps that have different rates. To describe their kinetics, the single-step kinetics approximation is often applied which resides in substituting a generally complex set of kinetic equations by the sole single-step kinetics equation. The main contribution of the single-step kinetics approximation is that it enables a mathematical description of the kinetics of solid-state reactions without a deeper insight into their mechanism. The single-step kinetics approximation is based on the assumption that the temperature and conversion functions are separable. In the paper, some consequences originating from ignoring the function separability are discussed.