Chemical equilibria, Le Chatelier's principle and Kc

Equilibrium and Kc

At dynamic equilibrium in a closed system, forward and reverse rates are equal and concentrations are constant. Le Chatelier's principle: if conditions change, the equilibrium shifts to oppose the change. For $a\mathrm{A}+b\mathrm{B}\rightleftharpoons c\mathrm{C}+d\mathrm{D}$, $K_c=\frac{[\mathrm{C}]^c[\mathrm{D}]^d}{[\mathrm{A}]^a[\mathrm{B}]^b}$ (products over reactants, powers = coefficients). Use an ICE table to find equilibrium concentrations. Only temperature changes $K_c$: for exothermic forward reactions, raising $T$ lowers $K_c$. Concentration and pressure changes shift the position but not $K_c$; catalysts change neither.