Past Papers Chemical Reaction Engineering

By: Prof. Fazal Rehman Shamil

Guess Paper 1: Chemical Reaction Engineering Fall – 2020 Past Papers

University Name – Confidential

Time Allowed: 3 hours

Total Marks:    70, Passing Marks (35)

Q.1 Attempt the following MCQs: 7*2=14
1- Fluid flow in a real packed bed can be approximated as __________ model.
A: plug flow B: dispersion C: mixed flow D: tank in series
2- Rate of an autocatalytic chemical reaction is a function of ___________.
A: temperature only B: pressure only C: composition only D: all (a), (b) and (c)
3- The unit of frequency factor in Arhenious equation is __________.
A: Same as that of the rate constant. B: same as that of activation energy. C: dimensionless. D: none of these.
4- The rate at which a chemical substance reacts is proportional to it’s ___________.
A: active mass B: equivalent weight C: molecular weight D: None of these
5- In autocatalytic reactions ________.
A: one of the reactants acts as a catalyst B: one of the products acts as a catalyst C: catalysts have very high selectivity D: no catalyst is used.
6- Equation shows the variation of __________ with temperature.
A: reaction rate B: rate constant C: energy of activation D: frequency factor.
7- What is the dispersion number for a CSTR? A: 0. B: <1. C: >1. D: ∞

Question No:02 7
A. Define Ideal Mixing Flow Reactor (CSTR).
B. Prove Performance equation for Ideal CSTR through the graphical method.

Question No: 03 7
A. Write any five applications of the Spray column reactor. Also, sketch Schematics for operational mechanisms.
B. What is the difference between Semi fluidized bed and Fixed fluidized bed reactors?

Question No: 04 7
A. Define Homogenous and heterogeneous reactions with different processes.
B. Elaborate “Arrhenius’ Law” with the mathematical expression for chemical reactions occurs at different Temperatures [T1 and T2].

Question No: 05 7
A. The chemical reaction of the stoichiometric equation. What is the order of reaction?
B. The pyrolysis of ethane proceeds with an activation energy of about 300 kJ/mol. How much faster is the decomposition at 650°C than at 500 °C?

Question No: 06 7
A. Define rate constant and derive its unit for nth Oder reaction.
B. Write the performance equation for the Batch and Plug flow reactor. Also, explain different parameters in the equation.

Question No: 07 7
A. Define Reactors and their different types.
B. Advantage and Disadvantage of Plug flow reactor as compared to CSTR.

Question No: 08 Attempt only Two Questions of your interest. 7
A. Explain the Zero Order Reaction; also write its mathematical equation for half-life.
B. Explain Spacetime and Space velocity with mathematical relation.
C. Write Activation Energy for chemical reaction with Graphical explanation.

Guess Paper 2: Chemical Reaction Engineering Spring – 2020 Past Papers

University Name – Confidential

Time Allowed: 3 hours

Total Marks:    70, Passing Marks (35)

Q.1 Attempt the following MCQs: 7*2=14
i. __________ explains the mechanism of catalysis. A. Activated complex theory B. Collision Theory C. Reaction Theory D. None of these
ii. A catalyst__________. A initiates a reaction 2. lowers the activation energy of reacting molecules 3. is capable of reacting with any one of the reactants. 4. can not be recovered chemically unchanged at the end of a chemical reaction.
iii. The rate constant of a chemical reaction decreases by decreasing the___________. A.pressure B. Temperature C. composition D. Reaction Time.
iv. Which of the following is the most suitable for very high pressure gas-phase reaction____________. A. Batch reactor B. Tubular flow reactor C. Stirred tank reactor D. Fluidised bed reactor.
v. The reaction between oxygen and organic material is a/an __________ reaction. A: Exothermic B. endothermic C. photochemical D. Biochemical
vi. When a catalyst increases the rate of chemical reaction, the rate constant_________
A: decreases B. increases C. remains constant D. becomes infinite.
vii. Catalytic action in a catalytic chemical reaction follows from the ability of the catalyst to change the ________. A: activation energy B: equilibrium constant C. heat of reaction D. None of these

Q.2: Pure gaseous reactant A (CAo= 100 millimole/liter) is fed at a steady rate into a mixed flow reactor (V = 0.1 liter) where it dimerizes (2A —–R). For different gas feed rates, the following data are obtained. Find a rate equation for this reaction.
Run: 1 2 3 4
V(Liter/hr): 10 3 1.2 0.5
Caf(milimol/liter): 85.7 66.7 50 33.4
Q. 3: 5+9
A. Define Chemical Reaction and Reactor.
B. Explain the Classification of the reactor on the base of its operation.

Q.4: Derive Designing Equation for CSTR using Law of Conservation of Mass.

Q.5: A. Define Recycle process in Reactor. Write its Mathematical Relation.
B. Explain the differences between Molecularity of reaction and Order of reaction.
Q.6: A. Define Space Time and Space Velocity.
B. Prove Designing Equation for Ideal Batch Reactor
Q.7: Write short notes on any two of the following: 7+7=14
A. Explain the effect of temperature on exothermic and endothermic reactions through Graphs.
B. Define Homogenous reactions and heterogeneous reactions with examples.
C. For first-order rate of reaction, write the integral method of analysis. Prove that –In (1- XA) =kt.

Guess Paper 3: Chemical Reaction Engineering Fall – 2019 Past Papers

University Name – Confidential

Time Allowed: 3 hours

Total Marks:    70, Passing Marks (35)

Q1: Choose the correct options. Each correct option carries 1 mark each.
1. Which one of the following statements about a chemical equation is true?
A. Mass is conserved B. Mass as well as atoms are conserved
C. Atoms are conserved D. Ions are conserved
2. A balanced chemical equation is in accordance with
A. law of gaseous volumes B. law of Avogadro C. law of constant proportions
D. law of conservation of mass
3. An imbalanced equation is against the
A .law of gaseous volumes B. law of constant proportions
C. law of conservation of mass D. law of multiple proportions
4. When a correctly written chemical equation is balanced
A. the number of atoms of each kind on each side should be equal
B. all molecules are diatomic C. all substances are in the same physical state
D. the sum of the coefficient on both sides is the same
5. Chemical reactions involve the participation of
A. electrons B. protons C. Neutrons D. nuclei
6. The symbolic representation of the molecule of a compound is called
A. structural formula B. molecular formula C. empirical formula
D. graphic formula
7. A chemical reaction occurs when the energy of the reacting molecules is
A. less than the activation energy of the reaction B. equal to the activation energy of the reaction C. more than the activation energy of the reaction
D. equal to or more than the activation energy of the reaction
8. The rate constant of a reaction depends on
A. the temperature of the system B. the time of reaction C. the extent of reaction
D. the initial concentration of the reactants
9. The reaction between neutral solution of barium chloride and sodium carbonate goes to completion because
A .the reaction is irreversible B. sodium chloride is only sparingly soluble in water
C. barium carbonate is almost insoluble in water
D. the solubility of BaCI2 decreases in the presence of sodium carbonate

10. A photochemical reaction is
A. catalyze by light B. initiated by light C. accompanied with emission of light
D. used to convert heat energy into light
11. Plants manufacture carbohydrates from the carbon dioxide of the atmosphere by
A. oxidation B. polymerization C. condensation with water D. a photochemical reaction
12. The rates of purely photochemical reactions do not depend on temperature to any significant extent because
A. they are exothermic reaction B. they are endothermic reactions
C. the energy of the reacting molecules exceeds the activation energy by absorption of light
D. they are reversible reactions
13. The reaction between organic material and oxygen is
A. an endothermic reaction B. an exothermic reaction C. a photochemical reaction D. a biochemical reaction
14. An exothermic reaction is that in which the reacting substances
A. have more energy than the products B. have less energy than the products
C. have as much energy as the products D. are at a higher temperature than the products

Q2: Discuss elementary and non-elementary reactions.

Q.3: What do you mean by order of a reaction? Explain zero, first, and second-order reactions.

Q4: Discuss the classification and rate of reaction in detail.

Q5: Derive a performance equation for a single fluid in an ideal plug flow reactor.

Q6: Find the first-order rate constant for the disappearance of A in the gas reaction 2A R if, on holding the pressure constant, the volume of the reaction mixture, starting with 80% A, decreases by 20% in 3 min.

Q7: Differentiate between integral method and differential method of analysis.

Q8: Write short notes on any two of the following:
a) Spray Column reactor
b) Moving bed catalytic reactor
c) Graphical representation of performance equation.

Guess Paper 1: Chemical Reaction Engineering Spring- 2019Past Papers

University Name – Confidential

Time Allowed: 3 hours

Total Marks:    70, Passing Marks (35)

Q1: Choose the correct options. Each correct option carries 1 mark each.
1. The space-velocity is the proper performance measure of flow reactors. The space-velocity has the units of
A. time B. (time)-1 C. velocity D. (velocity)-1
2. The space-velocity of 2 hr-1 means
A. That every two hours, one reactor volume of feed at specified conditions is being treated by the reactor.
B. that two-reactor volumes of feed at specified conditions are being fed into the reactor per hour
C. that the actual reactor volume is double that of the optimum reactor volume
D. that one-half reactor volume of feed at specified conditions are being fed into the reactor.
3. For constant-density systems, the performance equations are identical for
A. batch reactor and plug flow reactor B. batch reactor and back mix reactor
C. plug flow reactor and back mix reactor D. batch reactor, plug flow reactor, and back mix reactor.
4. For identical feed composition, flow rate, conversion and for all positive reaction orders, the ratio of volumes of the mixed reactor to the plug flow reactor is
A. always one B. always less than one C. always greater than one
D. equal to the order of the reaction.
5. The batch reactor has the disadvantage(s) of
A. high labor and handling cost B. Poorer quality control of the product
C. considerable shutdown time to empty, clean out and refill D. all of the above
6. For identical feed composition and flow rate, N plug flow reactors in series with a total volume V gives the same conversion as a single
A. plug flow reactor of volume V B. CSTR of volume V
C. Plug flow reactor of volume V/N D. plug flow reactor of volume NV.
7. N plug flow reactors in series with a total volume V gives the same conversion as a single plug flow reactor of volume V. The above statement is true for
A. zero-order reactions only B. First-order reactions only
C. Second-order reactions only D. all reaction orders.
8. The optimum size ratio for two mixed reactors in series is found in general to be dependent on the kinetics of the reaction and on the conversion level. For reaction order more than one
A. the larger reactor should come first B. the smaller reactor should come first
C. equal size reactors are best. D. None of these
9. Pure gaseous reactant A (CAO = 100 millimoles/liter) is fed at a steady rate into a mixed reactor where it dimerizes (2A  R). For a certain gas feed rate, the concentration of A in the exit stream is found to be 50 millimoles/liter. The fractional conversion of A is
A. 50% B.33.3 3% C. 40% D.66.67%
10. One liter per second of gaseous reactant A is introduced into a mixed reactor. The stoichiometry is A 3R, the conversion is 50% and under these conditions, the leaving flow rate is 2 liters per second. The space-time for this operation is
A. 1 sec B. sec C. 2 sec D. none
11. In question 109 the holding time is
A. sec B. sec C. 1 sec D.2 sec.
12. For a steady-state mixed reactor, the space-time is equivalent to the holding time for
A. constant fluid density systems B. variable fluid density systems
C. non-isothermal gas reactions D. gas reactions with changing a number of moles.
13. In an ideal plug flow reactor at steady state
A. there may be diffusion along the flow path B. there must be lateral mixing of fluid
C. the composition of the reactant remains constant along a flow path
D. the fractional conversion of the reactant varies from point to point along a flow path
14. in an ideal mixed reactor at steady-state
A. the composition throughout the reactor remains the same
B. the exit stream has the same composition as the fluid within the reactor
C. the space-time is equivalent to holding time for constant density systems D. all of these answers.

Q2: Discuss in detail homogenous and heterogeneous reactions.

Q.3: Discuss classification and rate of reaction in detail.

Q4: What are the principle factors involved in designing of a reactor?

Q5: Derive a performance equation for single fluid reacting in an ideal mixed flow reactor.

Q6: Find the first-order rate constant for the disappearance of A in the gas reaction 2A R if, on holding the pressure constant, the volume of the reaction mixture, starting with 70% A, decreases by 15% in 5 min.

Q7: Discuss the differential method for variable volume batch reactor.

Q8: Write short notes on any two of the following:
a) Order of a reaction.
b) Fluidized bed Reactor.
c) Packed Column Reactor

Prof. Fazal Rehman Shamil