The single-step approximation - Attributes, strong and weak sides

Mechanisms of the processes in condensed phase tend to occur in multiple steps that have different rates. Their kinetics is very often described by the single-step approximation. The first attribute of the approximation is the substitution of a generally complex set of kinetic equations describing the complex process by the sole single-step kinetic equation. The other attributes of the approximation are the separability of the temperature and conversion functions and the additivity. The temperature function for the best fit of experimental data may not be the Arrhenius relationship. The main strength of the single-step approximation is that it enables a mathematical description of the kinetics of solid-state reactions without a deeper insight into their mechanism. The low trustworthiness of far extrapolation is a weak point.