Page 298 - Elements of Chemical Reaction Engineering 3rd Edition

270 Collection and Analysis of Rate Data Chap. 5

P5-2, What if ...
(a) the reaction you were asked to apply the differential method of analysis
to determine the rate law for a reaction that is reversible at the tempera-
ture of interest?
(b) the gas-phase reaction you are studying in your laboratory were
extremely toxic. What precautions would you take?
P5-3A The irreversible isomerization

A-+B
was carried out in a batch reacfor and the following concentration-time data
were obtained:

t (min) 0 3 5 8 10 12 15 17.5
C, (mol/dm3) 4.0 2.89 2.25 1.45 1.0 0.65 0.25 0.07

(a) Determine the reaction order, a, and the specific reaction rate, k,.
(b) If you were to repeat this experiment to determine the kinetics, what
would you do differently? Would you run at a higher, lower, or the same
temperature? Take different data points? Explain.
(c) It is believed that the technician made a dilution error in the concentra-
tion measured at 17.5 min. What do you think? How do your answers
compare using regression (POLYMATH or other software) with those
obtained by graphical methods? (Am: (a) k = 0.2 (m~l/drn~)*~/min)
P5"4A The liquid-phase irreversible reaction
A+B+C

is carried out in a CSTR. To learn the rate law the volumetric flow rate, uo,
(hence T = V/u,) is varied and the effluent concentrations of species A
recorded as a function of the space time T. Pure A enters the reactor at a con-
centration of 2 moVdm3. Steady-state conditions exist when the measure-
ments are recorded.

C, (mol/dm3) 1.5 1.25 1.0 0.75 0.5

(a) Determine the reaction order and specific reaction rate.
(b) If you were to repeat this experiment to determine the kinetics, what
would you do differently? Would you run at a higher, lower, or the same
temperature? If you were to take more data, where would you place the
measurements (e.g., T)?
(c) It is believed that the technician may have made a dilution factor-of-10
error in one of the concentration measurements. What do you think? How
do your answers compare using regression (POLYMATH or other soft-
ware) with those obtained by graphical methods?
Note: All measurements were taken at steady-state conditions.