standard state

https://doi.org/10.1351/goldbook.S05925
State of a system chosen as standard for reference by convention. Three standard states are recognized: For a gas phase it is the (hypothetical) state of the pure substance in the gaseous phase at the standard pressure p=p⚬, assuming ideal behaviour. For a pure phase, or a mixture, or a solvent in the liquid or solid state it is the state of the pure substance in the liquid or solid phase at the standard pressure p=p⚬. For a solute in solution it is the (hypothetical) state of solute at the standard molality m⚬, standard pressure p⚬ or standard concentration c⚬ and exhibiting infinitely dilute solution behaviour. For a pure substance the concept of standard state applies to the substance in a well defined state of aggregation at a well defined but arbitrarily chosen standard pressure.
Source:
Green Book, 2nd ed., p. 53 [Terms] [Book]
Citation: 'standard state' 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.S05925 RIS BibTex EndNote
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Last revised: February 24, 2014