Le Chatelier's principle

A principle of chemical equilibrium: when a system at equilibrium is disturbed, it shifts to partially counteract the change in concentration, pressure, or temperature.

Chemical equilibrium: A state where forward and reverse reaction rates are equal, so concentrations no longer change over time. Le Chatelier's principle describes how these balanced systems respond when disturbed.
Haber–Bosch process: Industrial synthesis of ammonia from nitrogen and hydrogen over an iron catalyst at high pressure and temperature. Its high operating pressure exists precisely because ammonia formation shrinks gas volume.
Reversible reaction: A reaction that proceeds in both directions, allowing reactants and products to coexist at equilibrium. Reversibility is the precondition; a one-way reaction has nothing to shift.
Henry Louis Le Chatelier: French chemist and metallurgist who stated the equilibrium-shift principle in 1884. He derived the rule while working on cement and steel production chemistry.
Kinetic versus thermodynamic control: Two regimes of product distribution: the fastest-forming product versus the most stable one at equilibrium. Le Chatelier predicts equilibrium outcomes only, never rates or kinetic products.
Equilibrium constant: The ratio of product to reactant activities at equilibrium, fixed for a reaction at a given temperature. Only changes that alter this constant, like temperature shifts, permanently move an equilibrium.
Buffer solution: A solution of a weak acid and its conjugate base that resists pH change on adding acid or base. Buffers work by equilibrium shifts that consume added acid or base.
Reaction quotient: The instantaneous ratio of product to reactant activities, compared against the equilibrium constant to find the direction of change. Formally predicts the shift direction: the quotient moves toward the constant.
Fritz Haber: German chemist who demonstrated ammonia synthesis from nitrogen and hydrogen in 1909. His equilibrium analysis of ammonia synthesis put the principle to industrial work.
Steady state: A condition where concentrations stay constant because inflow balances outflow, not because forward and reverse rates match. Open living systems sit far from equilibrium, where the principle does not directly apply.

Linked from 32 pages