Page 40 - Introduction to chemical reaction engineering and kinetics

22 Chapter 1: Introduction

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alytically. However, as more realistic features of chemical reactor design are explored,
“OF
0 analytical solutions are often not possible, and the investigator must rely on software
packages capable of numerically solving the equations involved. Within this book, we
present both analytical and numerical techniques for solving problems in reactor design
and kinetics. The software used with this book is E-Z Solve. The icon shown in the
margin here is used similarly throughout the book to indicate where the software is
mentioned, or is employed in the solution of examples, or can be employed to advantage
in the solution of end-of-chapter problems. The software has several features essential
to solving problems in kinetics and reactor design. Thus, one can obtain
(1) Linear and nonlinear regressions of data for estimation of rate parameters;
(2) Solution of systems of nonlinear algebraic equations; and
(3) Numerical integration of systems of ordinary differential equations, including
“stiff)’ equations.
The E-Z Solve software also has a “sweep” feature that allows the user to perform
sensitivity analyses and examine a variety of design outcomes for a specified range of
parameter values. Consequently, it is also a powerful design and optimization tool.
Many of the examples throughout the book are solved with the E-Z Solve software.
In such cases, the computer file containing the program code and solution is cited. These
file names are of the form exa-b.msp, where “ex” designates an example problem, “a”
the chapter number, and “b” the example number within that chapter. These computer
files are included with the software package, and can be readily viewed by anyone who
has obtained the E-Z Solve software accompanying this text. Furthermore, these exam-
ple files can be manipulated so that end-of-chapter problems can be solved using the
software.

1.8 PROBLEMS FOR CHAPTER 1

l-l For the ammonia-synthesis reaction, NZ + 3H2 -+ 2NH3, if the rate of reaction with respect to
N2 is (--I~~), what is the rate with respect to (a) H2 and (b) NH3 in terms of (-?&)?
1-2 The rate law for the reaction CzHdBr, + 3KI -+ C& + 2KBr + KIs in an inert solvent, which
can be written as A + 3B --f products, has been found to be (-r-A) = k~c~ca, with the rate
constant kA = 1.34 L mol-’ h-l at 74.9”C (Dillon, 1932).
(a) For the rate of disappearance of KI, (-rg), what is the value of the rate constant kB?
(b) At what rate is KI being used up when the concentrations are CA = 0.022 and cn =
0.22 mol L-l?
(c) Do these values depend on the nature of the reactor in which the reaction is carried out?
(They were obtained by means of a constant-volume batch reactor.)
1-3 (a) In Example 1-4, of the 5 rate quantities ri (one for each species), how many are independent
(i.e., would need to be determined by experiment)?
(b) Choose a set of these to exclude ru,, and relate rn, to them.
1-4 For each of the following systems, determine C (number of components), a permissible set
of components, R (maximum number of independent chemical equations), and a proper set of
chemical equations to represent the stoichiometry. In each case, the system is represented by a
list of species followed by a list of elements.
(a) {(N&C104, Clz, NzO, NOCl, HCl, H20, N2,02, ClOz), (N, H, Cl, 0))relating to explosion
of N&Cl04 (cf. Segraves and Wickersham, 1991, equation (10)).
(b) {(C(gr), CO(g), COz(g), Zn(g), Zn(9, ZnO(s)), (C, 0, Zn)} relating to the production of
zinc metal (Denbigh, 1981, pp 191-193). (Zn(g) and Zn(e) are two different species of the
same substance Zn.)
(c) {(C12, NO, NOz, HCl, NzO, HzO, HN03, Nl!14C104, HC10402H20), (Cl, N, 0, H)}relating
to the production of perchloric acid (Jensen, 1987).