Thermodynamic conventions
Conventions, as an agreed way of doing things, appear throughout science, but they play a special role.[1] in thermodynamics where there is a general need to measure properties relatively rather than absolutely. For example, electrode potentials cannot be measured independently, only in couples as differences between so-called redox ‘half reactions’; so a convention is adopted which sets the value of the standard hydrogen electrode E0 = 0 V exactly, thus allowing all other electrode potentials to be quantified relative to that agreed standard. Examples of other thermodynamic conventions are[2][3][4][5][6]:
- Definition of the standard state of a liquid
- Definition of the sign given to work done by a system
- Definition as zero the enthalpy (heat content) of substances
- Definition as zero the Gibbs energy and enthalpy of formation of all the elements
- Definition as unity the thermodynamic activity of every pure solid or pure liquid (at standard pressure)
- Convention of sign of intermolecular forces: attractive forces negative and repulsive forces positive
- Symmetric convention for normalising activity coefficients using Raoult’s law
- Unsymmetric convention for normalising activity coefficients using Henry’s law
Many such conventional standards are defined by scientific authorities like the International Union of Pure and Applied Chemistry, Green book[7][8] as being the best practice for all scientists to follow. Most thermodynamic conventions establish a reference which is the given conventional property value for a particular substance under specified conditions of pressure and temperature. With these cases, the choice is usually straightforward and the selected references rarely change. Sometimes, however, the convention needs to be more complicated, which makes consensus more difficult to achieve. Three especially controversial instances have been described[1]. One of these concerns the definition of pH[9] so it has implications for topical debates concerning the rates of ocean acidification[10], CO2 uptake by carbonate precipitation[11], and hydrogen production by water electrolysis[12]
References
- ↑ 1.0 1.1 Filella, M.; May, E.F.; May, P.M. (2025). "Thermodynamic conventions". International Journal of Thermophysics. 46 (5). Bibcode:2025IJT....46...61F. doi:10.1007/s10765-025-03533-5. Unknown parameter
|article-number=ignored (help) - ↑ Glasstone, S. (1947). Thermodynamics for Chemists. New York, U.S.A.: D. Van Nostrand Co. Inc. ISBN 9781406773224. Search this book on
- ↑ Prausnitz, J.M.; Lichtenthaler, R.N.; de Azevedo, E.G. (1999). Molecular Thermodynamics of Fluid-Phase Equilibria (3rd ed.). Engelwood Cliffs, U.S.A.: Prentice Hall Inc. pp. 222–225. Search this book on
- ↑ Bridgman, P.W. (1941). The Nature of Thermodynamics. Cambridge, Mass., U.S.A.: Harvard Univ. Press. Search this book on
- ↑ Levine, I.N. (2002). Physical Chemistry (6th ed.). N.Y., U.S.A.: McGraw-Hill. Search this book on
- ↑ Anderson, G.H. (2005). Thermodynamics of Natural Systems (2nd ed.). Cambridge, U.K.: Cambridge University Press. Search this book on
- ↑ Cohen, E.R.; Cvitas, T.; Frey, J.G.; Holmström, B.; Kuchitsu, K.; Marquardt, R.; Mills, I.; Pavese, F.; Quack, M.; et al. (et al.) (2008). Quantities, Units and Symbols in Physical Chemistry, IUPAC Green Book (2nd Printing, 3rd ed.). Cambridge: IUPAC & RSC Publishing. Search this book on
- ↑ Brett, Christopher M A; Frey, Jeremy G; Hinde, Robert; Kuroda, Yutaka; Marquardt, Roberto; Pavese, Franco; Quack, Martin; Stohner, Jürgen; Thor, Anders J, eds. (2023). Quantities, Units and Symbols in Physical Chemistry (Abridged Version, 4th ed.). Royal Society of Chemistry. ISBN 978-1-83916-150-6. Search this book on
- ↑ May, P.M.; May, E.F. (2024). "Ion Trios: Cause of Ion Specific Interactions in Aqueous Solutions and Path to a Better pH Definition". ACS Omega. 9 (46): 46373–46386. doi:10.1021/acsomega.4c07525. PMC 11579776 Check
|pmc=value (help). PMID 39583676 Check|pmid=value (help). - ↑ Camaselle, S.; Velo, A.; Doval, M. D.; Broullón, D.; Pérez, F. F. (2024). "Long-term trends of pH, alkalinity, and hydrogen ion concentration in an upwelling-dominated coastal ecosystem: Ría de Vigo, NW Spain". Sci Rep. 14 (1). Bibcode:2024NatSR..1417929C. doi:10.1038/s41598-024-68694-z. PMC 11297135 Check
|pmc=value (help). PMID 39095574 Check|pmid=value (help). Unknown parameter|article-number=ignored (help) - ↑ Poulain, A.; Besselink, R.; Fernandez-Martínez, A.; Kellermeier, M.; Van Driessche, A.E.S. (2024). "A high-throughput approach for assessing antiscaling performance during mineral precipitation from seawater and hard water". npj Clean Water. 7. Bibcode:2024npjCW...7...30P. doi:10.1038/s41545-024-00324-7. Unknown parameter
|article-number=ignored (help) - ↑ Li, T.; Wang, B.; Cao, Y.; Liu, Z.; Wang, S.; Zhang, Q.; Sun, J.; Zhou, G. (2024). "Energy-saving hydrogen production by seawater electrolysis coupling tip-enhanced electric field promoted electrocatalytic sulfion oxidation". Nature Communications. 15 (1). Bibcode:2024NatCo..15.6173L. doi:10.1038/s41467-024-49931-5. PMC 11263359 Check
|pmc=value (help). PMID 39039041 Check|pmid=value (help). Unknown parameter|article-number=ignored (help)
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