Q uses the same formula as K but with current (instantaneous) concentrations, not equilibrium ones. Comparing Q to K predicts the direction: if Q < K, the forward reaction is favoured (products form to increase Q toward K). If Q > K, the reverse reaction is favoured (reactants form to decrease Q toward K). If Q = K, the system is at equilibrium. This is especially useful for Ksp problems: the ionic product (IP, analogous to Q) is compared with Ksp to determine whether precipitation occurs. IP > Ksp means supersaturated — precipitation occurs. IP < Ksp means unsaturated — more salt can dissolve. IP = Ksp means saturated — equilibrium.