The term refers to the relationship between the amounts of substances that react together
in a particular chemical reaction, and the amounts of products that are formed. The
provides the information that a
moles of A reacts with b
moles of B to produce y
moles of Y and z
moles of Z. The stoichiometry of a reaction may be unknown, or may be very complex.
For example, the thermal decomposition
of acetaldehyde yields mainly methane and carbon monoxide, but also a variety of
minor products such as ethane, acetone and diacetyl. The stoichiometric
is therefore only an approximate one. Even when the overall stoichiometry of a reaction
is well defined, it may be time-dependent in that it varies during the course of a
reaction. Thus if a reaction occurs by the mechanism
and X is formed in substantial amounts during the course of the process, the relationship
between the amounts of A, X and Y will vary with time, and no one stoichiometric
equation can represent the reaction at all times.
PAC, 1996, 68, 149
(A glossary of terms used in chemical kinetics, including reaction dynamics (IUPAC
on page 187
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. doi:10.1351/goldbook