What is Ionic Product of Water?

Ionic product of water: The dissociation of water, H₂ O⁺ ↔ H⁺ + OH^–

According to law of mass action, K = [H⁺] x [OH^–] / [H₂O]

or, K x [H₂O] = [H⁺] x [OH^–]

K_W is called ionic product of water whose value is 1 x 10^-4 at 25°C temperature. K_W is essentially just an equilibrium constant for the reactions.