The dissociation constant of water is represented by

$\mathrm{K}=\left[{\mathrm{H}}_3{\mathrm{O}}^{+}\right]\left[{\mathrm{OH}}^{-}\right]/\left[{\mathrm{H}}_2\mathrm{O}\right]$

or ${\mathrm{K}}_{\mathrm{w}}=\left[{\mathrm{H}}^{+}\right]\left[{\mathrm{OH}}^{-}\right]$

${\mathrm{K}}_{\mathrm{w}}$ is called

The dissociation constant is represented by

$\mathrm{K}=\left[{\mathrm{H}}_3{\mathrm{O}}^{+}\right]\left[{\mathrm{OH}}^{-}\right]/\left[{\mathrm{H}}_2\mathrm{O}\right]$

The concentration of water is omitted from the denominator as water is a pure liquid and its concentration remains constant. [${\mathrm{H}}_2\mathrm{O}$] is incorporated within the equilibrium constant to give a new constant, ${\mathrm{K}}_{\mathrm{w}}$, which is called the ionic product of water,

${\mathrm{K}}_{\mathrm{w}}=\left[{\mathrm{H}}^{+}\right]\left[{\mathrm{OH}}^{-}\right]$