⚖️

Le Chatelier's Principle

Perturb an equilibrium — the system shifts to oppose the change

Chemistry Equilibrium Thermodynamics Reaction Kinetics
Reaction:
[A] = 1.000 [B] = 1.000 [C] = 1.000 Kc = 1.000 Q = 1.000 Shift: —

⚖️ Le Chatelier's Principle

Le Chatelier's Principle (1884): If a system at chemical equilibrium is subjected to an external change (concentration, temperature, pressure), it will shift in the direction that partially counteracts that change, restoring a new equilibrium.

The reaction quotient Q compared to the equilibrium constant Kc predicts the shift direction:

Q < Kc → shifts right (→ more products)   Q > Kc → shifts left (→ more reactants)

Temperature effect: For exothermic reactions (ΔH < 0), increasing T decreases Kc (shifts left). For endothermic reactions, raising T increases Kc (shifts right). Pressure shifts equilibrium toward the side with fewer moles of gas.