Equilibrium constant vs rate constant - where kinetics meets thermodynamics?? The Equilibrium Law for aA + bB ⇌ cC + dD gives Kc = [C]c [D]d / [A]a x b at a given temperature. Kc* is also equal to the ratio of forward to reverse rate constants kfwd/krev. The rate expression for the forward and reverse reactions often does not follow the stoichiometric equation, and is of the form: rate = kfwd [A]mn rather than rate = kfwd[A]ab ie where m, n often does not equal a, b. At equilibrium, kfwd[A]ab = krev[C]c[D]d, so how is it that Kc can equal kfwd/krev … and how can the units of Kc equal those of kfwd / krev??