A concept related to
rate of reaction, particularly applicable to the progress in one direction only of component reaction
steps in a complex system or to the progress in one direction of reactions in a system
at dynamic equilibrium (in which there are no observable concentration changes with
time). Chemical flux is a derivative with respect to time, and has the dimensions
of
amount of substance per unit volume transformed per unit time. The sum of all the chemical fluxes leading
to destruction of B is designated the '
total chemical flux out of B'
(symbol
); the corresponding formation of B by concurrent elementary reactions is the '
total chemical flux into B or A'
(symbol
). For the mechanism:
the total chemical flux into C is caused by the single reaction (1):
whereas the chemical flux out of C is a sum over all reactions that remove C:
where
is the '
chemical flux out of C into B (and/or A)' and
is the '
chemical flux out of C into E'. The
rate of appearance of C is then given by:
In this system
(or
)
can be regarded as the hypothetical rate of decrease in the concentration of A due
to the single (unidirectional) reaction (1) proceeding in the assumed absence of all
other reactions. For a non-reversible reaction:
If two substances A and P are in
chemical equilibrium:
then:
and
Source:
PAC, 1994, 66, 1077
(Glossary of terms used in physical organic chemistry (IUPAC Recommendations 1994))
on page 1095
Cite as:
IUPAC. Compendium of Chemical Terminology, 2nd ed. (the "Gold Book"). Compiled by
A. D. McNaught and A. Wilkinson. Blackwell Scientific Publications, Oxford (1997).
XML on-line corrected version: http://goldbook.iupac.org (2006-) created by M. Nic,
J. Jirat, B. Kosata; updates compiled by A. Jenkins. ISBN 0-9678550-9-8.
https://doi.org/10.1351/goldbook.
