Reaction quotient
For a general equilibrium reaction; kA + mB ... cC + pD ...
Where;
{Ai} is the instantaneous activity of the species A,
{Bi} is the instantaneous activity of the species B,
{Ci} is the instantaneous activity of the species C,
{Di} is the instantaneous activity of the species D.
k, m, n, and p are the stoichiometric coefficients for the reaction.