Page 104 - Elements of Chemical Reaction Engineering Ebook

Sec. 3.1 Basic Definitions 75

For this type of reaction, the rate laws corresponding to a zero-, first-, second-,
third-order reaction, together with typical units for the corresponding rate con-
stants, are:
rA = kA:
Zero-order: - (3-6)
{ k} = m~l/(drn)~.
s

First-order: - (3-7)

Second-order: -rA = kACi: (3-8)
s
{ k} = (d~n)~/mol.

Third-order: -rA = kACi: (3-9)
{ k} = (dm3/mc11)~ ssl
*
Where do you find The activation energy, frequency factor, and reaction orders for a large
rate laws? number of gas- and liquid-phase reactions can be found in the National Bureau
of Standards’ ciirculars and ~upplements.~ Also consult the journals listed at the
end of Chapter 1.

3.1.3 Elementary Rate Laws and Molecularity

A reaction has an elementary rate law if the reaction order of each spe-
cies is identical with the stoichiometric coefficient of that species for the reac-
tion as written. For example, the oxidation of nitric oxide presented above has
an elementary rate law under this definition, while the phosgene synthesis
reaction does not. Another example of this type of reaction with an elementary
rate law is the gas-phase reaction between hydrogen and iodine to form h:ydro-
gen iodide:

for which the rate law is

[n some circles when a reaction has an elementary rate law it is referred
to as an elementary reaction. A more restrictive definition of an elementary
Very important
references, but you -
should also look in
the other literature Tables of Chemical Kinetics: Homogeneous Reactions, National Bureau of Standards
before going Circular 510 (Sept. 28, 1951); Suppl. 1 (Nov. 14, 1956); Suppl. 2 (Aug. 5, 1960);
to the lab Suppl. 3 (Sept. 15, 1961) (Washington, D.C.: U.S. Government Printing OFfice).
Chemical Kinetics and Photochemical Data for Use in Stratospheric Modeling, Eval-
uate No. 10, JPlL Publication 92-20, Aug. 15, 1992, Jet Propulsion Laboratories, Pas-
adena, Calif.