Question

what is the meaning of ionic product of water?

Answer 1

Ionic product of water is defined as the product of concentration of hydrogen ions (H⁺ ions) and hydroxyl ions (OH^- ions) obtained by the dissociation of water. It is denoted by the symbol K_w. It can be explained by the following equilibrium which exists in water

H₂O + H₂O ↔ H₃O⁺ + OH^-

The dissociation constant is represented by,
K = [H₃O⁺] [OH^–] / [H₂O]

As water is present in large amount, therefore its concentration remains constant and hence it can be omitted from the above expression. That is, [H₂O] is incorporated within the equilibrium constant to give a new constant, K_w, called the ionic product of water given as

K_w = [H⁺][OH^–]

An important point to note is that H⁺ and H₃O⁺ practically mean the same, and are often used interchangeably.