The law of mass action, as an equation for reaction kinetics (i.e., r_f), is necessarily true only for single-step or concerted reactions.
The law of mass action is necessarily true only for single-step. This is as an equation for reaction kinetics (i.e.). This is r_f. The law of mass action is necessarily true only for single-concerted reactions. This is as an equation for reaction kinetics (i.e.). This is r_f.