Equation for dissolving calcium carbonate in water: CaCO3(s) ⇄ Ca²⁺(aq) + CO₃²⁻(aq). The equilibrium constant expression for this reaction: K = [Ca²⁺] [CO₃²⁻] / [CaCO3(s)], but concentration of CaCO3(s) is 1 (for all solid), so the simpler expression for the equilibrium constant is:K = [Ca²⁺] [CO₃²⁻].
