pOH Definition

Expresses hydroxide-ion concentration on the same logarithmic scale as pH, letting you read the basic side of the equilibrium.

$$\mathrm{pOH}=-{\log }_{10}[\mathrm{O}{\mathrm{H}}^{-}]$$

Variables

Symbol	Meaning	Unit
$[\mathrm{O}{\mathrm{H}}^{-}]$	Hydroxide-ion concentration	mol/L

Worked example

For alkaline water at pH 8.5, pOH = 14 - 8.5 = 5.5, so [OH-] = 10^-5.5 = 3.16 x 10^-6 mol/L.

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Part of The Blueprint of Water