Free Chemical Reaction Engineering MCQs with Answers
395 Chemical Reaction Engineering MCQs from Chemical Engineering, each with the correct answer and a written explanation of why it is correct. Free and unlimited, with no account needed.
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395 questions · page 17 of 20
- A. 0
- B. > 150
- C. < 2100
- D. ∞
Explanation: Perfect mixing corresponds to maximum axial dispersion, so the dispersion number approaches infinity.
Correct answer: ∞- A. ∞
- B. > 1
- C. 1
- D. ≥ 1
Explanation: A finite number of mixed reactors in series only approximates plug flow.
Correct answer: ∞- A. Is same as heat of reaction at constant pressure
- B. Is the minimum energy which the molecules must have before the reaction can take place
- C. Varies as fifth power of the temperature
- D. Both B. and C.
Explanation: Activation energy is the energy barrier that reacting molecules must overcome for reaction to occur.
Correct answer: Is the minimum energy which the molecules must have before the reaction can take place- A. Same in both the reactors
- B. Higher in CSTR
- C. Higher in P.F. reactor
- D. Data insufficient; can't be predicted
Explanation: For a normal positive-order reaction, the plug-flow reactor maintains a higher reactant concentration over much of its length than the…
Correct answer: Higher in P.F. reactor- A. Usually equal to the residence time
- B. The reciprocal of the space velocity
- C. A measure of its capacity
- D. Both A. and B.
Explanation: Space time is reactor volume divided by inlet volumetric flow rate, and it is the reciprocal of space velocity.
Correct answer: Both A. and B.- A. Exothermic
- B. Autocatalytic
- C. Endothermic
- D. Autothermal
Explanation: In an autocatalytic reaction, the product promotes the reaction and partly offsets the decrease in reactant concentration as conversion…
Correct answer: Autocatalytic- A. Always equal to the total stoichiometric number of reactants
- B. An experimentally determined quantity
- C. Never fractional
- D. None of these
Explanation: Reaction order comes from the experimentally determined rate law, not directly from the stoichiometric equation.
Correct answer: An experimentally determined quantity- A. Increased temperature reduces the activation energy
- B. Collision frequency increases
- C. Fraction of molecules having threshold energy increases
- D. Value of threshold energy decreases
Explanation: From the Arrhenius equation, increasing temperature raises the fraction of molecules whose energy exceeds the activation or threshold…
Correct answer: Fraction of molecules having threshold energy increases- A. The composition of reactants remains constant along a flow path
- B. The conversion of the reactant varies from point to point along a flow path
- C. There is no lateral mixing of fluid
- D. There may be diffusion along the flow path
Explanation: In a plug-flow reactor, fluid elements move progressively downstream, so reactant conversion increases from point to point along the flow…
Correct answer: The conversion of the reactant varies from point to point along a flow path- A. Slurry
- B. Plug flow
- C. Homogeneous catalytic
- D. None of these
Explanation: Hydrogenation of vegetable oils uses a finely divided solid catalyst suspended in the liquid oil, with hydrogen gas dispersed through the…
Correct answer: Slurry- A. Freundlich
- B. Langmuir
- C. Tempkin
- D. None of these
Explanation: The BET equation extends the Langmuir monolayer adsorption concept to multilayer adsorption, allowing catalyst surface area to be…
Correct answer: Langmuir- A. First
- B. Zero
- C. Second
- D. Third
Explanation: For a second-order reaction, the half-life is t₁/₂ = 1/(kC_A0), so it is inversely proportional to the initial concentration.
Correct answer: Second- A. V
- B. V/n
- C. V.n
- D. 1/V
Explanation: PFR volumes in series add, and a series of ideal plug-flow sections behaves like one ideal PFR having the same total volume.
Correct answer: V- A. Linearly with time
- B. Exponentially with time
- C. Very abruptly towards the end of the reaction
- D. Logarithmically with time
Explanation: Integrating the first-order rate law gives C_A = C_A0e⁻ᵏᵗ, so concentration falls exponentially rather than linearly with time.
Correct answer: Exponentially with time- A. 3
- B. 4
- C. 6
- D. 10
Explanation: For first-order decay, each half-life reduces the remaining amount by half.
Correct answer: 4- A. None of the above
- B. Reaction
- C. External mass transfer
- D. Diffusion within the pellet
Explanation: A much lower concentration at the pellet centre than at its surface indicates a steep internal concentration gradient.
Correct answer: Diffusion within the pellet- A. Ideal tubular-flow reactor
- B. Batch reactor
- C. Slurry reactor
- D. CSTR
Explanation: Space time is based on reactor volume and inlet volumetric flow, making it convenient for sizing an ideal tubular-flow reactor.
Correct answer: Ideal tubular-flow reactor- A. Ideal plug flow
- B. Dead zone
- C. Bypass
- D. Channelling
Explanation: A long tail means some material remains in the packed bed much longer than the main flow, which indicates stagnant or dead regions.
Correct answer: Dead zone- A. Inversely proportional to
- B. Independent of
- C. Proportional to
- D. Proportional to the square of
Explanation: Without a chain mechanism, doubling the amount of catalyst doubles the available active surface and hence the overall rate, provided…
Correct answer: Proportional to- A. Decreases
- B. Remains unchanged
- C. Increases
- D. Unpredictable from the data
Explanation: For an exothermic reversible reaction, increasing temperature shifts equilibrium toward the reactants, so the equilibrium conversion…
Correct answer: Decreases