Final Exam Fall 2014

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Final Exam (160 pts total)Chemical Reaction Engineering

December 18, 2014

Name______________________________________________________

Read the exam through first. Please write legibly. Answer all questions completely, clearlyindicating final answers and showing work. Closed book, notes and electronics.

Problem 1. (12 pts) Given the pulse tracer graphs and the total number of ideal reactors, draw

the reactors in series for the system. (While multiple configurations may be valid, please only

give one situation per case)

# Reactors in Series Pulser Tracer Plot Reactors in Series Schematic

1

2

2

1

3

3


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Name_________________________________________________ Final Exam, Fall 2014

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Problem 2. (12 pts) Explain what chemical chain reactions are; how they start, continue and

stop; what concerns are related to them; and provide an example of a chain reaction (4-6sentences).

Problem 3.(10 pts) What are the two types of mass transfer that control overall rates? How

does this integrate into the kinetics of a system? Support your answer with example(s) from

project 2. (3-4 sentences)


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Problem 4. (16 pts) Wild turkeys have become a problem on an island of farms and woodland

because they destroy the crops and forest undergrowth. In a brilliant move, the farmers decide

to introduce rattlesnakes on the island to eat the turkey eggs and thereby control the turkeypopulation (folklore says some states did this, but no substantiated evidence exists for this).

There were originally 1000 turkeys when 20 rattlesnakes were introduced.

If we simplify this system and ignore the egg incubation time, we can say all turkey eggs countas turkeys and all snake eggs count as snakes. The following data may be used: turkeys eat

greens and they reproduce at a rate proportional to the supply of greens; rattlesnakes eat turkey

(eggs) and reproduce at a rate proportion to the supply of turkey (eggs). Turkeys have a natural

lifetime of 4 years and rattlesnakes have a natural lifetime of 10 years*.

*Data provided is fictional.

a)

Write out the mass balances for turkeys and rattlesnakes in terms of rate constants, kis,and concentrations of species.

b) In your opinion, what will happen to the balance of turkeys and snakes over a short timeperiod and long time period? (2-3 sentences)


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Problem 5. (25 pts) Urea decomposes into ammonia and carbon dioxide when catalyzed by the

enzyme Urease. The following set of reactions occur in the presence of water:

Urea + Urease Urea-Urease

Urea-Urease

2NH3+ CO2+ Urease

The following data for urea decomposition is given:

CUrea(kmol/m ) 0.2 0.02 0.01 0.005 0.002

-rUrea(kmol/ m sec) 1.08 0.55 0.38 0.2 0.09

a) What are the values of the Michaelis-Menton parameters Vmaxand KM?

b) What is the physical meaning of Vmax? (1 sentence)

c) If you have non-competitive inhibition, how would the curve compare to no inhibition

(show a qualitative plot, pointing out the key features)?


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Problem 6. (25 pts) The surface reaction rate for an irreversible 2nd

order reaction AB was

found to be 8.67x10-11

mol/(cm2sec) when the concentration of A was 0.50M a catalyst with a

surface area of 450 m2/g, a density of 3.5 g/cm

3and a void fraction of 0.3 was used.

a) What is the pseudohomogeneous rate equation for this system?

b) What reactor volume will you need to process 2.6 M A to 75% conversion in a packed

bed reactor? The flowrate into the reactor is 20 L/sec.


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Problem 7. (25 pts) Your waste treatment pond is aerated through a series of pumps situated at

the bottom of the pond to keep the oxygen levels saturated at 1.5x10-3

M. 4D (your toxic

compound) reacts with oxygen to degrade into 2 Rs (a benign compound). Normally, yourwaste must process for 2 months to get D from 2.5x10

-5M down to the EPA permitted level of

3.6x10-7

M. The reaction has been found to experimentally be first order in D.

The local turtle population has adapted to survive in D, but as a result have turned veryaggressive. The alpha-male turtle tried to make lunch out of your pumps at the bottom of the

pond and you are too afraid to go out and retrieve the pump to replace it. Instead, you decide to

create a continuous treatment system where you are now feeding a stream of oxygen at 9.8x10-4

M and D at 2.5x10-5

M into a 2000 gallon tank. What is the residence time you will need to haveto get D down to the permitted level?


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Problem 8.(15pts) Butadiene (C4H6) is synthesized by the catalytic dehydrogenation of butane

(C4H8). You are running your reaction at 625C and feeding butane in a 50:50 (mol) mixture

with nitrogen.

What is the equilibrium conversion if the Gibbs free energy of reaction at 625C is 10.62

kJ/mol?


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Problem 9. (20 pts) Answer the questions using the plot below where in an adiabatic reactor

AB in with the initial concentration of A being 2.33M.

a)

What is To?

b)

What is/are the steady state(s) of the system? Give reactor conversion and temperature.

c) What is the heat of reaction for this system?

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Final Exam Fall 2014