Page 112 - Introduction to chemical reaction engineering and kinetics

94 Chapter 5: Complex Systems
Table 5.1 Stoichiometric table in terms of [j for Example 5-2

Species i Initial Change 6 Fi
noncomponents
c o 0 Fco 51 = Fcoll 51
co2 0 Fco, t2 = Fco,ll
HCHO 0 Fncno 5 3 = FncnoIl ii
components
Cfi FCH4,0 Fcn4,0 - 51 - 52 - b
0 2 Fo2.o Fo,, - $5 - 252 - 5;
H2O 0 251 + 252 + 5 3
total: Fcn4.0 + Fo,,o Fcn4,0 f Fo2.0 + $5

Using the chemical system and equations (l), (2), and (3) of Example 5-1, construct a
stoichiometric table, based on the use of tj, to show the molar flow rates of all six species.
Assume experimental data are available for the flow rates (or equivalent) of CO, CO,, and
HCHO as noncomponents.

SOLUTION

The table can be displayed as Table 5.1, with both sj and Fi obtained from equation 5.2-11,
applied to noncomponents and components in turn.

5.3 REVERSIBLE REACTIONS

5.3.1 Net Rate and Forms of Rate Law
Consider a reversible reaction involving reactants A, B, . . . and products C, D, . . .
written as:

b‘4lA + MB + . ..&C+ v,D + . . . (5.3-1)
r,
We assume that the experimental (net) rate of reaction, r, is the difference between the
forward rate, rf, and the reverse rate, ‘;:

‘D -
r=TA= . . . = - - rf(ci, T, . . .) - r,(ci, T, . . .) (5.3-2)
VA VD
If the effects of T and ci are separable, then equation 5.3-2 may be written

r = Q(Tkf(cd - k,(T)g,(c,) (5.3-3)

where k, and k, are forward and reverse rate constants, respectively.
If, further, a power rate law of the form of equation 4.1-3 is applicable, then

r = kf(T) ficsi - k,.(T) fit;’ (5.3-4)
i = l i = l