Autoionization of Water

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Topics > Acids & Bases > Autoionization of Water

Definition: Autoionization (or self-ionization) of water refers to the process where two water molecules react to produce a hydronium ion (H3O+) and a hydroxide ion (OH−).

Water Dissociation Constant (Kw)

Definition:Kwis the equilibrium constant for the autoionization of water.

Expression:Kw=[H3O+][OH−]

Value at 25°C: Kw=1.0×10−14at 25°C (298K). This value varies with temperature.

Ion Product of Water

The ion product of water ([H3O+][OH−]) is always constant at a given temperature.

In pure water at 25°C, the concentrations of H3O+andOH−are both1.0×10−7 M.

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