$word_{count}$: 230

Chemical equilibrium is a dynamic state where forward and reverse reaction rates are equal. The equilibrium constant Kc = [products]^n / [reactants]^m (pure solids and liquids excluded). Kp uses partial pressures: Kp = Kc(RT)^delta_n_{gas}. Key manipulations: reversing a reaction inverts K; multiplying by n raises K to the nth power; adding reactions multiplies their K values. The reaction quotient Q uses non-equilibrium concentrations to predict direction: Q < K (forward), Q > K (reverse), Q = K (equilibrium). Le Chatelier's principle governs shifts: concentration changes shift away from the added species; pressure increases shift toward fewer gas moles; temperature changes shift toward endothermic direction. Critically, only temperature changes alter K itself — concentration, pressure, and catalysts do not. A catalyst accelerates attainment of equilibrium without changing K or position. Adding inert gas at constant volume has no effect, but at constant pressure it shifts toward more gas moles. The van't Hoff equation ln$\frac{K2}{K1}$ = $\frac{delta_H}{R}$(1/T1 - 1/T2) quantifies temperature dependence.