9.2 Equilibrium Constants and Reaction Quotients

Equilibrium Constants

The equilibrium constant, K, is the ratio of products to reactants at equilibrium. It is taken by raising the equilibrium concentrations of each species to its coefficient. So, for the reaction ${aA + bB ⇋ cC + dD}$, the equilibrium constant would be ${\frac{[C]^c[D]^d}{[A]^a[B]^b}}$. K has a fixed value for a reaction at a certain temperature. As solids and liquids are incompressible, note that the concentrations of pure solids and liquids are unchanging and therefore left out of the equilibrium expression.