Law of Mass Action
The principle that the rate of a reaction is proportional to the product of the active masses of the reactants.
Formula / equation
K = [C]^c[D]^d / [A]^a[B]^b
Unit
Various
In depth
Formulated by Guldberg and Waage, the law leads directly to the equilibrium constant expression, in which products appear in the numerator and reactants in the denominator, each raised to its stoichiometric coefficient. It is the foundation of all quantitative equilibrium calculation.
Examples in the real world
For N₂ + 3H₂ ⇌ 2NH₃ the law gives K = [NH₃]² / ([N₂][H₂]³).