Chemical Equilibrium
The state of a reversible reaction in which the forward and reverse reactions proceed at equal rates, so no net change in composition occurs.
Formula / equation
aA + bB ⇌ cC + dD
Unit
Dimensionless
In depth
Equilibrium is reached only in a closed system and can be approached from either direction, arriving at the same composition. Concentrations remain constant but are not necessarily equal, and the reaction has not stopped — it has merely become balanced. At equilibrium the Gibbs energy of the system is at a minimum.
Examples in the real world
N₂ + 3H₂ ⇌ 2NH₃ in a sealed reactor settling to a fixed mixture of all three gases.