The units of rate constants in chemical kinetics
The units of rate constants in chemical kinetics
This short article discusses the units of rate constants as used in chemical kinetics and, in particular, the aspect of non-integral powers of base units, which some might find unusual for units in the SI system. In many ways the fact that the units of the rate constants as usually defined convey information about the order of the reaction or reactions involved is very useful, but in other ways having the same (or at least very similar) quantity that has different units under different conditions is not so desirable. Furthermore, just as with chemical equilibrium constants, taking functions of the rate constant (such as the logarithm when representing the Arrhenius equation in the form ln kvs.1/T) needs special attention. Here we examine a possible alternative definition of rate constants in terms of an explicit ratio to the concentration standard state and although we acknowledge that this approach unlikely to be adopted by the community, it serves as a basis to discuss the meaning of rate constants.
Chemical kinetics, Dimensions, Rate constants, Units
Frey, Jeremy G.
ba60c559-c4af-44f1-87e6-ce69819bf23f
Wallington, T.J.
bead2cd4-cbf4-4ece-92a2-c14712b6d0a4
Hartshorn, Richard
36033568-d6d4-4197-a475-f4e70745ee6b
Quack, Martin
0bda0702-024c-41ea-9081-0d3015747d58
Heus, Pascal
f20f30e8-65c1-4b76-9b58-82277918c3a3
Emmerson, Steven
93c1001f-68e0-457d-806b-f42f98c831cd
Frey, Jeremy G.
ba60c559-c4af-44f1-87e6-ce69819bf23f
Wallington, T.J.
bead2cd4-cbf4-4ece-92a2-c14712b6d0a4
Hartshorn, Richard
36033568-d6d4-4197-a475-f4e70745ee6b
Quack, Martin
0bda0702-024c-41ea-9081-0d3015747d58
Heus, Pascal
f20f30e8-65c1-4b76-9b58-82277918c3a3
Emmerson, Steven
93c1001f-68e0-457d-806b-f42f98c831cd
Frey, Jeremy G., Wallington, T.J., Hartshorn, Richard, Quack, Martin, Heus, Pascal and Emmerson, Steven
(2022)
The units of rate constants in chemical kinetics.
Accreditation and Quality Assurance, 2022 (10).
(doi:10.1007/s00769-022-01515-w).
Abstract
This short article discusses the units of rate constants as used in chemical kinetics and, in particular, the aspect of non-integral powers of base units, which some might find unusual for units in the SI system. In many ways the fact that the units of the rate constants as usually defined convey information about the order of the reaction or reactions involved is very useful, but in other ways having the same (or at least very similar) quantity that has different units under different conditions is not so desirable. Furthermore, just as with chemical equilibrium constants, taking functions of the rate constant (such as the logarithm when representing the Arrhenius equation in the form ln kvs.1/T) needs special attention. Here we examine a possible alternative definition of rate constants in terms of an explicit ratio to the concentration standard state and although we acknowledge that this approach unlikely to be adopted by the community, it serves as a basis to discuss the meaning of rate constants.
Text
149b02bf-e68c-4830-93f9-71e113e1c77d
- Version of Record
More information
Accepted/In Press date: 19 June 2022
e-pub ahead of print date: 11 October 2022
Additional Information:
Publisher Copyright:
© 2022, The Author(s).
Keywords:
Chemical kinetics, Dimensions, Rate constants, Units
Identifiers
Local EPrints ID: 476212
URI: http://eprints.soton.ac.uk/id/eprint/476212
ISSN: 0949-1775
PURE UUID: cf3f8125-a735-427e-b0ad-e81482f3d2e6
Catalogue record
Date deposited: 14 Apr 2023 16:38
Last modified: 06 Jun 2024 01:32
Export record
Altmetrics
Contributors
Author:
T.J. Wallington
Author:
Richard Hartshorn
Author:
Martin Quack
Author:
Pascal Heus
Author:
Steven Emmerson
Download statistics
Downloads from ePrints over the past year. Other digital versions may also be available to download e.g. from the publisher's website.
View more statistics
