Title: activity
Long Title: IUPAC Gold Book - activity
DOI: 10.1351/goldbook.A00115
Status: current
Index: quantity

Definition
Defined by the equation \[a = e^{\frac{\mu - \mu^{o}}{R\,T}}\] where \(R\) is the gas constant, \(T\) the thermodynamic temperature, \(\mu\) the chemical potential and \(\mu^{o}\) the standard chemical potential the definition of which depends on the choice of the standard state.

Related Terms
- absolute activity: https://goldbook.iupac.org/terms/view/A00019
- chemical potential: https://goldbook.iupac.org/terms/view/C01032
- gas constant: https://goldbook.iupac.org/terms/view/G02579
- standard chemical potential: https://goldbook.iupac.org/terms/view/S05908
- standard state: https://goldbook.iupac.org/terms/view/S05925
- thermodynamic temperature: https://goldbook.iupac.org/terms/view/T06321

Sources
- Green Book, 2nd ed., p. 49 (https://goldbook.iupac.org/files/pdf/green_book_2ed.pdf)
- PAC, 1996, 68, 957. 'Glossary of terms in quantities and units in Clinical Chemistry (IUPAC-IFCC Recommendations 1996)' on page 989 (https://doi.org/10.1351/pac199668040957)

Other Outputs
- html: https://goldbook.iupac.org/terms/view/A00115/html
- json: https://goldbook.iupac.org/terms/view/A00115/json
- xml: https://goldbook.iupac.org/terms/view/A00115/xml

Citation: Citation: 'activity' in IUPAC Compendium of Chemical Terminology, 5th ed. International Union of Pure and Applied Chemistry; 2025. Online version 5.0.0, 2025. 10.1351/goldbook.A00115
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Disclaimer: The International Union of Pure and Applied Chemistry (IUPAC) is continuously reviewing and, where needed, updating terms in the Compendium of Chemical Terminology (the IUPAC Gold Book). Users of these terms are encouraged to include the version of a term with its use and to check regularly for updates to term definitions that you are using.
Accessed: 2026-05-13T21:31:05+00:00