Chemical equilibrium: definition in chemistry
Chemical equilibrium: The state of a reversible reaction in which the forward and reverse reactions happen at the same rate, so the amounts of reactants and products stay constant.
Equilibrium is dynamic: both reactions keep going, but because they balance, no overall change can be seen. The ratio of products to reactants at equilibrium is described by the equilibrium constant, K. According to Le Chatelier's principle, if a condition such as concentration, pressure or temperature changes, the equilibrium shifts to counteract the change, which industry uses to increase yields.
Examples
- N₂ + 3H₂ ⇌ 2NH₃ in the Haber process for making ammonia
- Brown NO₂ and colorless N₂O₄ in a sealed tube: 2NO₂ ⇌ N₂O₄
- Acetic acid partly ionizing in water: CH₃COOH ⇌ CH₃COO⁻ + H⁺
- A saturated salt solution with undissolved salt at the bottom