Equilibrium << `ee` kwuh LIHB ree uhm >>, Chemical, is a state of balance between a pair of forward and reverse chemical reactions. A double arrow in a chemical equation such as the one below indicates equilibrium. At equilibrium, the rate of the forward reaction (left to right in the equation) is equal to the rate of the reverse reaction (right to left).
N2 + 3H2 ⇌ 2NH3
In the forward reaction illustrated by the above equation, nitrogen, N2, is combining with hydrogen, H2, to form ammonia, NH3. In the reverse reaction illustrated by the equation, ammonia is breaking up into nitrogen and hydrogen. At equilibrium, the concentrations of the various substances do not change. In general, temperature and pressure affect the concentrations of chemicals in an equilibrium mixture.
