Term: autoprotolysis constant
https://doi.org/10.1351/goldbook.A00532

Definition:
The product of the activities (or, more approximately, concentrations) of the species produced as the result of autoprotolysis. For solvents in which no other ionization processes are significant the term is synonymous with 'ionic product'. The autoprotolysis constant for water, Kw, is equal to the product of activities: \[a\left(\text{H}_{3}\text{O}^{\text{+}}\right)\ a\left(\text{OH}^{\text{-}}\right) = 1.0\times 10^{-14}\] at 25°C.

Related Terms:
1) autoprotolysis (http://doi.org/10.1351/goldbook.A00531).
2) ionization (http://doi.org/10.1351/goldbook.I03183).

Source: PAC, 1994, 66, 1077. 'Glossary of terms used in physical organic chemistry (IUPAC Recommendations 1994)' on page 1087 (https://doi.org/10.1351/pac199466051077)

Citation: 'autoprotolysis constant' in IUPAC Compendium of Chemical Terminology, 5th ed. International Union of Pure and Applied Chemistry; 2025. Online version 5.0.0, 2025. https://doi.org/10.1351/goldbook.A00532

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