Editing Standard state (section)

=== Solutes ===
For a substance in solution (solute), the standard state {{not a typo|C°}} is usually chosen as the hypothetical state it would have at the standard state [[molality]] or [[amount concentration]] but exhibiting infinite-dilution behavior (where there are no solute-solute interactions, but solute-solvent interactions are present).<ref name="libretext"/> The reason for this unusual definition is that the behavior of a solute at the limit of infinite dilution is described by equations which are very similar to the equations for ideal gases. Hence taking infinite-dilution behavior to be the standard state allows corrections for non-ideality to be made consistently for all the different solutes. The standard state molality is {{val|1|u=mol/kg}}, while the standard state molarity is {{val|1|u=mol/dm3}}.

Other choices are possible. For example, the use of a standard state concentration of 10<sup>−7</sup>&nbsp;mol/L for the hydrogen ion in a real, aqueous solution is common in the field of [[biochemistry]].<ref>{{cite book |last1=Chang |first1=Raymond | last2=Thoman | first2=John W. Jr. |title=Physical Chemistry for the Chemical Sciences |date=2014|publisher=University Science Books |location=New York |pages=346–347}}</ref><ref>{{cite book |last1=Sherwood |first1=Dennis |last2=Dalby |first2=Paul |title=Modern Thermodynamics for Chemists and Biochemists |date=2018 |publisher=Oxford Scholarship Online |doi=10.1093/oso/9780198782957.003.0023 |isbn=978-0-19-878295-7 |url=https://oxford.universitypressscholarship.com/view/10.1093/oso/9780198782957.001.0001/oso-9780198782957-chapter-23 |access-date=18 May 2021}}</ref> In other application areas such as [[electrochemistry]], the standard state is sometimes chosen as the actual state of the real solution at a standard concentration (often {{val|1|u=mol/dm3}}).<ref>{{cite book |last1=Chang |first1=Raymond | last2=Thoman | first2=John W. Jr. |title=Physical Chemistry for the Chemical Sciences |date=2014 |publisher=University Science Books |location=New York |pages=228–231}}</ref> The [[activity coefficients]] will not transfer from convention to convention and so it is very important to know and understand what conventions were used in the construction of tables of standard thermodynamic properties before using them to describe solutions.