The existence of an equilibrium and its chemical relation with the composition of the system, actually found from the study of rates of some reversible reactions before the thermodynamic approach developed.
Therefore, C.M Guldberg and P. Waage expressed the dependence of concentrations on the rate of reaction in a general form known as the law of mass action.
They also recognized that chemical equilibrium is a dynamic equilibrium and not a static equilibrium.
When we discuss all the topics related to equilibrium we can’t discuss it on one page of the website. Therefore some of the topic related equilibrium reaction discuss below,