<Dd> K = (S) σ (T) τ...(A) α (B) β...(\ displaystyle K = (\ frac ((S) ^ (\ sigma) (T) ^ (\ tau) \ dots) ((A) ^ (\ alpha) (B) ^ (\ beta) \ dots)) \,) </Dd> <P> is correct even from the modern perspective, apart from the use of concentrations instead of activities (the concept of chemical activity was developed by Josiah Willard Gibbs, in the 1870s, but was not widely known in Europe until the 1890s). The derivation from the reaction rate expressions is no longer considered to be valid . Nevertheless, Guldberg and Waage were on the right track when they suggested that the driving force for both forward and backward reactions is equal when the mixture is at equilibrium . The term they used for this force was chemical affinity . Today the expression for the equilibrium constant is derived by setting the chemical potential of forward and backward reactions to be equal . The generalisation of the Law of Mass Action, in terms of affinity, to equilibria of arbitrary stoichiometry was a bold and correct conjecture . </P> <P> The hypothesis that reaction rate is proportional to reactant concentrations is, strictly speaking, only true for elementary reactions (reactions with a single mechanistic step), but the empirical rate expression </P> <Dl> <Dd> r f = k f (A) (B) (\ displaystyle r_ (f) = k_ (f) (A) (B) \,) </Dd> </Dl>

What is the law of mass action examples