Equilibrium Constant
This characterises the chemical equilibrium which occurs between the reagents and the products of a reaction.
The value of this thermodynamic constant, denoted by K, can be calculated from the thermodynamic data by using the relation
ln K = - DrG°m / RT
where DrG°m is the reference molar enthalpy of the reaction under consideration.
K can also be calculated starting from the activities, aB, measured at equilibrium, of each component B of the reaction, characterized by the stoichiometric equation
aA + cC = mM + nN
Under these conditions, K is obtained starting from the relation:
where B is an unspecified constituent of the reaction appearing in the stoichiometric equation with the stoichiometric number n(B).
Keq = [M]m [N]n / [A]a [C]c