Page 82 - Introduction to chemical reaction engineering and kinetics
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Chapter 4
Development of the Rate
Law for a Simple System
In this chapter, we describe how experimental rate data, obtained as described in Chap-
ter 3, can be developed into a quantitative rate law for a simple, single-phase system.
We first recapitulate the form of the rate law, and, as in Chapter 3, we consider only
the effects of concentration and temperature; we assume that these effects are separa-
ble into reaction order and Arrhenius parameters. We point out the choice of units for
concentration in gas-phase reactions and some consequences of this choice for the Ar-
rhenius parameters. We then proceed, mainly by examples, to illustrate various reaction
orders and compare the consequences of the use of different types of reactors. Finally,
we illustrate the determination of Arrhenius parameters for the effect of temperature
on rate.
4.1 THE RATE LAW
4.1.1 Form of Rate Law Used
Throughout this chapter, we refer to a single-phase, irreversible reaction corresponding
to the stoichiometric equation 1.4-7:
-$ viAi = 0 (4.1-1)
i = l
where N is the number of reacting species, both “reactants” and “products”; for a re-
actant, vi is negative, and for a product, it is positive, by convention.
The corresponding reaction is written in the manner of reaction (A) in Section 3.1.2:
(qjA+ IvB(B +... -+ vr,D + vnE+... (4.1-2)
We assume that the rate law for this reaction has the form, from equations 3.1-2 and
1.4-8,
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