Chemical equilibrium is defined as the state of a chemical reaction at which the rates of forward and reverse reactions are equal and the concentration of reactants and products reach constant value.
Important aspects of chemical equilibrium:
(1) At equilibrium, the rates of forward and reverse reactions are equal.
(2) All the reactants and products are present at equilibrium.
(3) The concentrations of the reactants and products reach constant values and these are called equilibrium concentrations.
(4) A catalyst does not affect the position of equilibrium.
(5) The changes in concentration, pressure, volume and temperature can change the equilibrium position.