Page 118 - Elements of Chemical Reaction Engineering 3rd Edition

90 Rate Laws and Stoichiometry Chap. 3

I (b) For 90% conversion:

Let US find CB:

-
C - 10 - - = lO(O.2-0.3) = - 1 mol/dm3
B- [l?o O:)
Negative concentration-impossible!
The basis of Ninety percent conversion of NaOH is not possible, because glyceryl stearate
calculation should is the limiting reactant. Consequently, all the glyceryl stearate is used up before
be the limiting 90% of the NaOH could be reacted. It is important to choose the limiting reactant
reactant
as the basis of calculation.

3.3.3 Flow Systems

The form of the stoichiometric table for a continuous-flow system (see
Figure 3-2) is virtually identical to that for a batch system (Table 3-2) except
that we replace N,, by 4o and N, by < (Table 3-3). Taking A as the basis,
divide Equation (2-1) through by the stoichiometric coefficient of A to obtain

b c d
A+ - B j -C+-D
a a a
For a flow system, the concentration C, at a given point can be determined
from FA and the volumetrjc flow rate u at that point:

Definition of c,=-= moleshime - moles
FA
concentration for (3-27)
flow system u literskime --I liter
Units of v are typically given in terms of liters per second, cubic decime-
ters per second, or cubic feet per minute. We now caq write the concentrations
of A, B, C, and D for the general reaction given by Equation (2-2) in terms of
the entering molar flow rate ( FA, , FBO, F,, , FDo), the conversion X, and the
volumetric flow rate, u.