The autoionization of water can be represented by the following chemical equation:
H2O (l) ⇌ H+ (aq) + OH- (aq)
At 25°C, the equilibrium constant for this reaction is given by:
Kw = [H+][OH-] = 1.0 × 10^-14
where [H+] is the molar concentration of hydrogen ions in the solution and [OH-] is the molar concentration of hydroxide ions in the solution.
The expression for the autoionization of water at 25°C is:
w = [H+][OH-] = 1.0 × 10^-14
where w is the ion product of water. At 25°C, the value of w is equal to 1.0 × 10^-14, which is a constant for pure water at this temperature.