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Le Chatelier's Principle

Le Chatelier's principle describes how a system at equilibrium responds to changes in conditions such as pressure, temperature, or concentration.
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The statement of the theorem

Consider a system at equilibrium, defined by the reaction quotient QQ and the equilibrium constant KK: Q=KQ = K. If a change in external conditions (concentration CC, pressure PP, or temperature TT) is applied, the system shifts to restore equilibrium. For a change in concentration, let ΔC\Delta C be the change in concentration of a species. The system adjusts such that the rate of reaction rr changes to maintain the equilibrium condition: ddt(Q−K)=0\frac{d}{dt} (Q - K) = 0. For temperature changes, the dependence of KK on TT is governed by the van't Hoff equation: dlnKd(1/T)=−ΔH∘R\frac{d\text{ln}K}{d(1/T)} = -\frac{\Delta H^{\circ}}{R}.