CHEMICAL REACTIONS ENGINEERING

Additional Problems
1. For the given data, propose a rate law for FOR NUMBERS 6-7
the reaction A → P by determining the Given the zero-order gas phase decomposition A →
order and the rate constant. 2.7R, in a constant-volume bomb starting with 80%
[A] (M) -r (M/s) A, 20% inert, we have the following data given in
A
the table.
0.01 0.00047
Time (s) Total Pressure (atm)
0.05 0.0015
0 1
0.75 0.013
1 1.5
1 0.017
6. If we introduce A at a total pressure of 10
1.5 0.0212
atm, no inert, what will be the total pressure
2 0.027
at t = 1?
5 0.053
a. 10
10 0.09 b. 10.5
a. k = 0.0158, n = 0.677 c. 11
b. k = 0.0158, n = 0.766 d. 11.5
c. k = 0.0581, n = 0.677
d. k = 0.0581, n = 0.766 7. If we introduce A at a partial pressure of 1
atm and inert at a partial pressure of 9 atm,
2. Given the reaction A → B, initially pure gas what will be the total pressure at t = 1?
A was fed to the reactor with an initial a. 10
pressure of 8.2 atm at 500 K. With k = 10 b. 10.5
L/mol-s, if the reactor used was a constant c. 11
volume batch reactor, calculate the d. 11.5
residence time for 90% conversion.
a. 1.8 s 8. What is the maximum % increase in total
b. 3.3 s volume expected for the batch, isobaric,
c. 4.5 s gaseous decomposition 2A → 2R + S if the
d. 6.9 s feed contained 25% inert?
a. 35.7%
3. The gas-phase decomposition A → B + 2C b. 37.5%
is carried out in a constant-volume batch c. 53.7%
reactor. Determine the reaction order and d. 57.3%
the rate constant.
C (M) t (min) 9. A first order reaction 2A → R took place in
AO 1/2
0.075 1.3 a constant pressure setup which resulted in
0.05 1.96 a 20 % decrease in reactor volume after 3
0.025 4.1 minutes. It was noted that initially, the
0.0133 7.7 reactor contained only 20 % inert and the
0.01 9.8 rest A. What is the rate constant?
a. n = 1, k = 10.26 a. 0.213
b. n = 1, k = 26.01 b. 0.231
c. n = 2, k = 10.26 c. 0.312
d. n = 2, k = 26.01 d. 0.321

4. The first order reversible liquid reaction A 10. A gas decomposes at 900 OC according to:
↔ R takes place in a batch reactor. After 8 2A(g) → 2R(g) + S(g) with the rate constant
minutes, the conversion of A is 33.3% of 1000 cm3/mol-s. Using pure A, calculate
while equilibrium conversion is 66.7%. the time it will take to react 80% of A in a
Find a rate equation for this reaction. batch reactor at 900 OC and 1 atm in
a. k2 = 0.02879, k1 = 0.05767 minutes.
b. k2 = 0.02879, k1 = 0.06757 a. 6.11 min
c. k2 = 0.07289, k1 = 0.05767 b. 7.22 min
d. k2 = 0.07289, k1 = 0.06757 c. 8.33 min
d. 9.44 min
5. The gas phase reaction A → B + C is
carried out isothermally in a 20 L constant 11. When the first-order homogenous gas-
volume batch reactor. 20 mol of pure A is phase decomposition A → 2.5R is carried
initially placed in the reactor. The reactor is out in an isothermal batch reactor at 2 atm
well mixed. If the temperature is 400.15 K, with 20% inert present, the volume
what is the final total pressure assuming increases by 60% in 20 mins. When the
that the reaction goes to completion? reaction is carried out in a constant-volume
a. 56.76 atm reactor, find the time required for the
b. 65.67 atm pressure to reach 8 atm if the initial
c. 67.65 atm pressure is 5 atm, 2 atm of which consists
d. 76.56 atm of inert.
CHEMICAL REACTIONS ENGINEERING
Additional Problems
a. 31.7 min 17. A fluid flows through 2 stirred tank reactors
b. 37.1 min in series. Each reactor has a capacity of
c. 71.3 min 40,000 liters and the fluid enters at 100
d. 73.1 min L/hr. The fluid undergoes 1st order decay
with a half-life of 24 hrs. Find the %
12. The gas phase decomposition: 1.5A → 2R conversion of the fluid, assuming an initial
when studied in an isothermal constant concentration of 1 M.
volume batch reactor gave the same half- a. 9.94%
life of 20 min for different feed b. 49.9%
compositions. If the same reaction is c. 94.9%
conducted at the same temperature in a d. 99.4%
constant pressure batch reactor using a feed
consisting of 80%A, 20% Inert by mole, 18. The liquid reaction 1.5A → 2R when
what will be the % increase in the total studied in an isothermal 200 L batch reactor
volume after 1 hour? gave the same half-life of 35 min for
a. 23.33% different feed compositions. Suppose the
b. 32.33% same reaction is conducted at the same
c. 33.23% temp in four equally sized backmix reactors
d. 33.32% in series. What is the space time for 85 %
conversion?
13. An isothermal, gas phase reaction 2A → P a. 30.64
is to be carried out in a variable volume b. 34.06
batch reactor. The feed composed of 60% A c. 36.04
(rest inert) enters at 5 atm and 80 °C. The d. 43.06
specific rate of reaction is 2.8 cm3/mol-s at
50 °C with E = 15400 cal/mol. Calculate 19. The liquid phase reaction A → B + C is
the time required for reactant A to be conducted isothermally at 50 °C in a
reduced to half its initial concentration. CSTR. The inlet concentration of A is 8.0
a. 408 s gmol/L. At a space time of 5 minutes, the
b. 480 s concentration of A at the exit is 4.0 gmol/L.
c. 804 s The kinetics of the reaction are described
d. 840 s by the equation –rA = kCA0.5. A plug flow
reactor of the same volume is added in
FOR NUMBERS 14-15 series after the CSTR. What is the
A homogeneous liquid phase reaction X →Y -rX = concentration of A in gmol/L at the exit of
kCx2 takes place with a 50% conversion in a mixed the PFR?
flow reactor. a. 1 M
14. What will be the conversion if this reactor b. 1.5 M
is replaced by another mixed flow reactor c. 2 M
having a volume 6 times that of original d. 2.5 M
reactor?
a. 0.57 20. Two CSTRs are in series for a first order
b. 0.67 reaction. Forty percent conversion is
c. 0.75 obtained in the first CSTR. What is the
d. 0.81 relative size of the second reactor,
compared to the first, to obtain 80% overall
15. What will be the conversion if the original conversion?
reactor is replaced by a PFR of same size? a. V/3
a. 0.57 b. V/2
b. 0.67 c. 2V
c. 0.75 d. 3V
d. 0.81

16. An aqueous feed of A and B (400 L/min,

0.1 M A, 0.2 M B) is to be converted to
product in a mixed flow reactor. The
kinetics of the reaction are represented by
A + B → R, -rA = 200CACB. Find the
volume of reactor needed for 99.9%
conversion of A to product.
a. 19904.06 L
b. 19906.04 L
c. 19940.06 L
d. 19960.04 L