# Chemical Reaction Engineering MCQ (Multiple Choice Questions)

1. What is the chemical reaction rate?
a) Chemical reaction rate is a chemical property
b) Chemical reaction rate is a physical property
c) Chemical reaction rate is an intensive property
d) Chemical reaction rate is an extensive property

Explanation: Chemical reaction rate depends on temperature and concentration. Hence, it is an intensive property.

2. The study of rates at which chemical reactions occur and the effect of various parameters on the rate are termed as ____
a) Fluid Mechanics
b) Chemical Technology
c) Chemical Sciences
d) Chemical Kinetics

Explanation: Chemical Kinetics is the study of rate of chemical reaction and the effect of parameters like temperature, pressure, concentration, etc. on reaction rates. Kinetic studies help in obtaining information about reaction mechanism and transition states.

3. If $$\frac{τ}{t}=\frac{1}{3},$$ average conversion for a particle B of constant size in a mixed flow reactor for chemical reaction controlling is?
a) 0.75
b) 0.92
c) 0.76
d) 0.98

Explanation: $$\overline{X_{(B)}} = 3(\frac{\overline{t}}{τ}) -6 (\frac{\overline{t}}{τ})^2+ 6(\frac{\overline{t}}{τ})^3(1-e^\frac{τ}{\overline{t}}, 1-\overline{X_{(B)}}$$ = 0.078 and $$\overline{X_{(B)}}$$ = 0.92

4. Catalyst is a substance that ___________
a) Can either increase or decrease the speed of a chemical reaction
b) Alters the value of equilibrium constant in a reversible chemical reaction
c) Increases the speed of a chemical reaction
d) Decreases the speed of a chemical reaction

Explanation: Catalyst is a substance that increases the speed of reaction without consuming itself at the end of the reaction, and the phenomenon is called catalysis. There are some catalysts that decrease the speed of reaction and these catalysts are called negative catalysts.

5. For mixed flow of particles containing a single unchanging size and uniform gas composition, the fraction unconverted for chemical reaction controlling is?
a) $$\int_0^τ$$(1-$$\frac{t}{τ}$$)0.5$$\frac{e}{t}^\frac{-t}{t}$$ dt
b) $$\int_0^τ$$(1-$$\frac{t}{τ}$$)$$\frac{e}{t}^\frac{-t}{t}$$ dt
c) $$\int_0^τ$$(1-$$\frac{t}{τ}$$)2$$\frac{e}{t}^\frac{-t}{t}$$ dt
d) $$\int_0^τ$$(1-$$\frac{t}{τ}$$)3$$\frac{e}{t}^\frac{-t}{t}$$ dt

Explanation: For chemical reaction controlling, $$\frac{t}{τ}$$ = 1-(1- XB)$$^\frac{1}{3}$$. Hence, 1-$$\overline{X_{(B)}}$$ = ∫0τ(1-$$\frac{t}{τ}$$)3$$\frac{e}{t}^\frac{-t}{t}$$ dt.

6. Which of the following is true for fluidized catalytic beds?
a) There is no pressure drop
b) They come under the category of batch reactors
c) The bulk density is a function of the flow rate through the bed
d) They cannot be used for multi-phase chemical reactions

Explanation: Fluidized catalytic beds are mostly used for multi-phase reactions, for example, cumene decomposition. They come under flow reactors. The inclusion of fluidized bed offers more resistance to flow and hence results in a pressure drop.

7. In which of the following reaction the rate of reaction is a function of rate constant alone is?
a) Zero order reaction
b) Third order reaction
c) First order reaction
d) Second order reaction

Explanation: Zero order reaction is the one in which rate does not depend on concentration.
(-r) = k
k → Rate constant

8. Which of the following represents heterogeneous catalytic reaction?
a) Reduction of iron ore
b) Ammonia synthesis
c) Burning of coal
d) Roasting of ores

Explanation: Ammonia synthesis is a heterogeneous reaction. Iron is used as a catalyst in the synthesis of ammonia by Haber’s process.

9. If rate of a zero order reaction is 10 $$\frac{mol}{m^3×s}$$ and reaction time is 5s, then the value of rate constant is ____
a) 2 s-1
b) 5 s-1
c) 10 s-1
d) 1 s-1

Explanation: (-rA) = kCAn
10 = k (5)
Hence, k = 2 s-1.

10. Which of the following is the most suitable reactor for the pharmaceutical industry?
a) PBR
b) MFR
c) PFR
d) Batch reactor

Explanation: When small scale production is desired, high or stringent quality standards to be met batch reactors used extensively.

11. If the conversion of a first-order liquid phase reaction occurring in a CSTR is 75%, molar feed rate is 5 mol/min, the rate of the reaction is 5 $$\frac{mol}{litre.min}$$ then the volume of the reactor (in litre) is?
a) 0.33
b) 0.4
c) 0.75
d) 0.5

Explanation: For a CSTR, the performance equation is FA0XA = (-rA)V
FA0 is molar feed rate and XA is the fractional conversion
5 × 0.75 = 5 × V
V = 0.75 L

12. The rate constant of a first order reaction depends on the _____________
a) Temperature
b) Concentration
c) Time
d) Pressure

Explanation: The reaction rate constant depends on temperature only.

13. Which of the following is an example of autocatalytic reaction?
a) Oxidation of copper
b) Ammonia formation reaction
c) Hydrogen peroxide decomposition reaction
d) Reaction of permanganate with oxalic acid

Explanation: Permanganate in acidic medium oxidises the oxalic acid. This reaction produces Mn2+ ions, which in turn catalyses the reaction.

14. Which of the following reactor arrangements causes fast deactivation?
a) Fluidised bed reactor
b) Batch for fluid and solid
c) Plug flow for fluid
d) Mixed flow for fluid

Explanation: Fluidisation causes high catalytic deactivation. The catalytic particles are well mixed by the reactant fluid.

15. Which of the following is not a reversible reaction?
a) Oxidation of sulphur dioxide to sulphur trioxide
b) Ammonia formation from its elements
c) Formation of hydrogen bromide from its elements
d) Decomposition reaction of nitrogen pentoxide

Explanation: The reaction of hydrogen with bromine is irreversible reaction. H2 + Br2 → HBr.

16. If τ = 5 s, first order rate constant, k = 0.25 sec-1 and the number of tanks, N is 5, then the conversion is?
a) 87.45%
b) 33%
c) 75%
d) 67.2%

Explanation: XA = 1-$$\frac{1}{(1+\frac{τk}{N})^N}$$
1-$$\frac{1}{(1+\frac{5×0.25}{5})^5}$$ = 67.2%.

17. The catalyst in a first-order chemical reaction changes the
a) Activation energy
b) Equilibrium constant
c) Heat of reaction
d) Heat of formation of the product

Explanation: A catalyst in a first-order chemical reaction changes the Activation energy.

18. Which of the following is the correct expression for the rate of a reaction?
a) $$\frac{Moles \, unreacted}{Volume \, of \, fluid×Time}$$
b) $$\frac{Moles \, of \, product \, formed}{Volume \, of \, fluid}$$
c) $$\frac{Moles \, of \, product \, formed}{Volume \, of \, fluid×Time}$$
d) $$\frac{Moles \, of \, reactant \, initially \, taken}{Volume \, of \, fluid×Time}$$

Explanation: Rate of the reaction is the number of moles of the reactant component disappearing per unit volume per unit time. The moles of the product formed are the number of moles of the reactant species disappearing during the course of reaction.

19. The rate of reaction is rapid for which of the following reactions?
a) Gas reactions in porous catalysts
b) Reactions in rocket engines
c) Cellular reactions
d) Reactions in coal furnaces

Explanation: The rate of reaction in rocket engines is in the range 105-108. The order of decrease in rates is, Reactions in rocket engines > Reactions in coal furnaces > Gas reactions in porous catalysts > Cellular reactions.

20. The activation energy of a reaction is 155326 J/ mol. The rate constant of the reaction at and 300K as a function of rate constant at 400K, obtained by the Collision theory is?
a) k1 = 1.2 × 10-7 k2
b) k1 = 1.5 × 10-6 k2
c) k1 = 1.2 × 10-6 k2
d) k1 = 1.5 × 10-7k2

Explanation: By collision theory, ln($$\frac{k_2}{k_1}) = -\frac{E}{R} (\frac{1}{T_2} – \frac{1}{T_1}) + 0.5ln(\frac{T_2}{T_1})$$
ln($$\frac{k_2}{k_1}) = -\frac{155326}{8.314}(\frac{1}{400} – \frac{1}{300}) + 0.5ln(\frac{400}{300})$$
Hence, k1 = 1.5 × 10-7k2.

21. Which of the following is an isomerisation reaction?
a) Conversion of glucose to fructose
b) Combustion reactions
c) Formation of ammonia from hydrogen and nitrogen
d) Decomposition of hydrogen peroxide to hydrogen and oxygen

Explanation: Isomerisation is the process in which one molecule gets transformed into another molecule that has absolutely the same atoms which are arranged in a different way. Glucose and fructose, share the same molecular formula: C6H12O6. Although all they have the same molecular formula, the arrangement of atoms differs.

22. For a first order reaction, the rate constant as a function of half life is given as ____
a) 0.6931
b) $$\frac{k}{0.6931}$$
c) $$\frac{0.6931}{k}$$
d) 0.6931×k

Explanation: Half life period is the time taken for one-half of the reactant to be consumed. For a first order reaction, ($$\frac{-dC}{dt}$$) = kCn. Integrating between initial concentration CA0 and final concentration $$\frac{C_{A0}}{2}$$, ln(2) = kt0.5
t0.5 = $$\frac{0.6931}{k}.$$

23. Which of the following theories does not propose the temperature dependence of rate constant?
a) Transition state theory
b) Bohr’s theory
c) Arrhenius theory
d) Collision theory

Explanation: Bohr’s theory proposes the model of an atom. Arrhenius theory, Collision theory, Transition state theory propose the variation of rate constant with temperature.

24. What is the unit of activation energy?
a) J/ mol
b) K
c) mol
d) mol.K

Explanation: Activation energy is expressed in J/ mol or kJ/ mol. Activation energy is the energy required for a chemical reaction to occur.

25. If CA is the final concentration and CA0 is the initial concentration, the conversion of a reaction is expressed as ____
a) $$\frac{C_A}{(C_{A0})}$$
b) $$\frac{C_{A0}-C_A}{(-r_A)V}$$
c) $$\frac{C_{A0}-C_A}{(-r_A)}$$
d) $$\frac{C_{A0}-C_A}{(C_{A0})}$$

Explanation: Conversion in a chemical reaction is the ratio of the amount of reactant consumed to form products to the amount of reactant fed. If the entire reactant is converted to product, then the conversion is 100%.

26. Which of the following is true for gas-phase reactions?
a) Decrease in moles of product increases the volume of the reaction mixture
b) Increase in moles of product does not affect the volume of the reaction mixture
c) Increase in moles of product increases the volume of the reaction mixture
d) Increase in moles of product decreases the volume of the reaction mixture

Explanation: Increase in moles of product increases reaction mixture volume. For a reaction proceeding such that the moles of products are higher than moles of reactants, volume of reaction mixture increases.

27. Which of the following is NOT a part of reactor design?
a) Flow rates of the reactant and product streams
b) Method of operation
c) Type of the reactor
d) Size of the reactor

Explanation: In general, most reactors are not a stand-alone unit. They are part of huge plants. This means that the flow rates of reactant and/or product streams depend on a lot of factors and may even be pre-decided. The purpose of reactor design, therefore, is to determine the reactor size and type and the suitable method of operation to meet the flow rate or other requirements.

28. Consider the liquid reaction 3A + 2B → 4C
What could be the outlet composition if CAo = 100 mol/L in a batch reactor and the feed is an equimolar mixture of A and B? Assume that 5 mol of C was already present in the reactor initially.
a) XA = 0.6, CB = 60, Cc = 80
b) XA = 0.2, CB = 86.66, Cc = 31.66
c) XA = 0.8, CB = 43.33, Cc = 106.66
d) XA = 0.4, CB = 76.66, Cc = 58.33

Explanation: Taking A as the key reactant and using material balance we get,
CB = CAo*(1 – 2*XA/3)
Cc = CAo*(5/100 + 4*XA/3)

29. Reaction corresponding to stoichiometric equation is called __________
a) Non-elementary
b) Elementary
c) Heterogeneous
d) Homogeneous

Explanation: Elementary reactions are the ones with single reaction step and the reaction rate corresponds to stoichiometric equation.

30. Which of the following reactions follows elementary rate law?
a) Reversible catalytic decomposition of isopropylbenzene
b) Formation of hydrogen bromide
c) Vapor phase decomposition of ethanal
d) Cis-trans isomerization

Explanation: Cis-trans isomerization follows elementary rate laws. Hydrogen bromide formation reaction, as well as the reversible catalytic decomposition of isopropylbenzene, are non-elementary in nature. Rate of vapor phase decomposition of ethanal is proportional to Cethanal3/2.

31. How much time required to convert to a fraction of 0.7 for a first order reaction?
a) t0.7 = $$\frac{(-0.3)}{C_{A0} k}$$
b) t0.7 = $$\frac{(0.3)}{C_{A0} k}$$
c) t0.7 = $$\frac{(-0.7)}{C_{A0} k}$$
d) t0.7 = $$\frac{(0.7)}{C_{A0} k}$$

Explanation: The time for converting to any fraction, F is, tF = $$\frac{C_{A0}^{1-n}(F^{n-1}-1)}{(n-1)k}.$$ At F = 0.7, t0.7 = $$\frac{C_{A0}^{1-2}(0.7^1- 1)}{k}.$$

32. Which of the following is true for the rate law of a reversible reaction?
a) Rate law can be written only in terms of concentrations
b) It reduces to irreversible form when product concentration is zero
c) It satisfies thermodynamic relationships at all times
d) Rate law can be written only in terms of partial pressures

Explanation: Rate law can be written in terms of both concentrations or partial pressures. The thermodynamic relationships are satisfied only at equilibrium. If the product concentration is zero, the rate of the backward reaction becomes zero and the rate law reduces to irreversible form.

33. Which of the following constants is a type of equilibrium constant?
a) Association constant
b) Solubility
c) Decay constant
d) Dissociation constant

Explanation: Decay constant is actually a type of rate constant, for a given decay reaction. Solubility, association and dissociation constants are equilibrium constants. These are reaction quotients calculated at the stag of ionic equilibrium w.r.t various ionic and non-ionic species present in a system.

34. A liquid phase reaction occurring in adiabatic PFR has a heat of reaction -120000 J/molK. Specific heat of the stream is 10000 J / molK. The temperature difference for complete conversion to be achieved is ___
a) 83.33K
b) 560 K
c) 8.33 K
d) 12 K

Explanation: $$\frac{C_p ∆T}{-H_R}$$ = XA
XA = 1 for complete conversion.
∆T = $$\frac{120000}{10000}$$ = 12 K.

35. Which of the following represents series type deactivation model? (Where R is the product and P is the poison)
a) A → R + P↓
b) A → R → P↓
c) A → R, A → P
d) A → P↓

Explanation: The series deactivation is the mechanism in which the product may decompose to produce the poison or further react to produce the poison. The poison deposits on the catalyst and causes deactivation.

36. What is the activity of a catalyst when a time t = 0?
a) Unity
b) ∞
c) Zero
d) Negative

Explanation: When the reaction has not yet started to occur, the catalyst surface is not poisoned. The entire surface on the catalyst is available to promote the reaction. At a time t=0, the activity is the highest and equal to 1. The value of ‘a’ lies between 0 and 1 as ‘a’ is the ratio of rate of reaction achieved by the catalyst at any given time to the maximum rate that can be achieved by a fresh catalyst.

37. Which of the following represents second order bimolecular type reversible reaction?
a) A+B ↔ R
b) A ↔ R+S
c) A ↔ B
d) A+B ↔ R+S

Explanation: Bimolecular reaction involves 2 molecules. Both reactants and products react simultaneously.

38. Which of the following is not a characteristic of tracer?
a) Easily detectable
b) Adsorbance onto the reactor surface
c) Inertness
d) Non – reactive

Explanation: The tracer should not stick to the walls or other surfaces of reactor. The physical properties of the tracer should be similar to that of the system.

39. If the total pressure for reaction is initially is 2 atm and the pressure is changed to 3 atm for the reaction to occur, then the value of (PA – PA0) for the reaction N2O → N2 + 0.5O2 is?
a) -1
b) 1
c) -2
d) 2

Explanation: ∆n = 0.5
pA = pA0 – $$\frac{a}{∆n}$$ (P – P0)
(PA = PA0) = $$\frac{-1}{0.5}$$(3-2)
(PA = PA0) = -2.

40. The final concentration of product is related to the yield as ____
a) Final concentration = Yield / Reactant fed
b) Final concentration = Yield × Reactant converted
c) Final concentration = Yield × Reactant fed
d) Final concentration = Yield / Reactant fed

Explanation: Yield = $$\frac{Product \, formed}{Reactant \, converted}$$
Product formed = Yield × Reactant converted.

## Chapterwise Multiple Choice Questions on Chemical Reaction Engineering

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## 1. Chemical Reaction Engineering MCQ on Basic Concepts

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## 2. Chemical Reaction Engineering MCQ on Elements of Reaction Kinetics

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## 3. Chemical Reaction Engineering MCQ on Kinetics of Homogeneous Reactions

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## 7. Chemical Reaction Engineering MCQ on Isothermal Reactor Design

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## 8. Chemical Reaction Engineering MCQ on Collection and Analysis of Rate Data

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## 13. Chemical Reaction Engineering MCQ on Catalyst Deactivation

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## 17. Chemical Reaction Engineering MCQ on Compartment Models, Models for Non Ideal Reactors

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## 18. Chemical Reaction Engineering MCQ on Microbial Fermentation

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