According to the Law of Mass Action, for a reversible chemical reaction at a constant temperature, the equilibrium constant ($K_c$) is the ratio of the product of molar concentrations of the products to that of the reactants, with each concentration term raised to a power equal to its stoichiometric coefficient in the balanced equation. For the synthesis of ammonia: $N_2(g)+3H_2(g)\rightleftharpoons 2N{H}_3(g)$ $K_c=\frac{[N{H}_3{]}^2}{[N_2{]}^1[H_2{]}^3}$

• Square brackets $[]$ denote molarity ($mol/L$).