# 8.20: Untitled Page 209

## Chapter 8

Figure 8.13b. Transient process in a perfectly mixed stirred tank reactor desired reactor volume is achieved. During the transient period when the volume is given by V( t)  V Q t , the exit flow rate is constant at Q . In this o

1

o

problem you are asked to determine the exit concentration during this transient period.

Section 8.3

8‐14. Consider the process studied in Example 8.1, subject to an initial condition of the form,

I.C.

o

o

c

c , c

c ,

t  0

A

A

B

B

and determine the concentration of species A as a function of time.

8‐15. For the process studied in Example 8.1, assume that the equilibrium coefficient and the first order rate coefficient have the values

1

1

K

 10 ,

k

 10 min

(1)

eq

1

and determine the time, t required for the concentration of species A to be given 1

by

o

c   c  0 9

. 9  c

c

,

t t

(2)

A

A

o

A eq

A

1

Here  c  represents the equilibrium concentration.

A eq

Transient Material Balances

391

8‐16. In this problem we consider the heated, semi‐batch reactor shown in Figure 8.16 where we have identified the vapor phase as the   phase and the liquid phase as the   phase . This reactor has been designed to determine the Figure 8.16. Semi‐batch reactor for determination of chemical kinetics chemical kinetics of the dehydration of t‐butyl alcohol (species A) to produce isobutylene (species B) and water (species C). The system is initially charged with t‐butyl alcohol; a catalyst is then added which causes the dehydration of the alcohol to form isobutylene and water. The isobutylene escapes through the top of the reactor while the water and t‐butyl alcohol are condensed and remain in the reactor. If one measures the concentration of the t‐butyl alcohol in the liquid phase, the rate of reaction can be determined and that is the objective of this particular experiment.

392