Reaction rates and affinities in consequtive reaction

The pattern of chemical affinity of the intermediate formation step in first-order and second order consecutive reactions was described. When the stationary state approximation can be applied, the chemical affinity of the intermediate formation reaction is practically constant. This premise was used to establish a quantitative criterion of stationary concentration of the intermediate. Criterion defines the relative difference between the rate of formation and rate of decay of the intermediate. The smaller is the value of the said criterion, the more reliable becomes the assumption that the concentration of the intermediate is in steady state.