Law of Chemical Equilibrium

At equilibrium,

The rate of forward reaction = Rate of backward reactionThe above mathematical equation is called the Law Of Chemical Equilibrium.

The product of the molar concentration of the products, each raised to the power equal to its stoichiometric coefficients divided by the product of the molar concentration of the reactants, each raised to the power equal to its stoichiometric coefficients is constant at constant temperature and is called Equilibrium constant.

For Gas Phase Reactions

The equilibrium constant can be expressed in terms of the partial pressures of the reactants and the products. If expressed in terms of partial pressure, it is denoted by K_p.

Where P_A , P_B , P_C , P_D  are the partial pressure of A ,B ,C , D in the reaction mixture.