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 16 of 20
- A. keff = k + kg
- B. 1/keff = 1/k + 1/kg
- C. keff = (kkg)1/2
- D. keff = (k+ kg)/2
Explanation: External mass transfer and surface reaction act as consecutive resistances, so their reciprocal effective rate constants add: 1/k_eff =…
Correct answer: 1/keff = 1/k + 1/kg- A. XA/(1 - XA)Vs η
- B. XA Vs ln η
- C. XA Vs . η
- D. XA(1 - XA)Vs η
Explanation: For a zero-order reaction in a CSTR, the design equation gives τ = C_A0 X_A/k, so conversion is directly proportional to residence time.
Correct answer: XA Vs . η- A. At the inlet
- B. Averaged over the inlet and outlet
- C. In the reactor
- D. At the outlet
Explanation: The E-curve is the exit age distribution, so it describes the age distribution of fluid elements as they leave the reactor.
Correct answer: At the outlet- A. 1
- B. 0
- C. ∞
- D. √2π
Explanation: E(t) is a normalized probability density for the exit ages of fluid elements.
Correct answer: 1- A. Solid catalysts
- B. Darkness
- C. Sunlight
- D. Monochromatic radiation only
Explanation: Photochemical reactions require radiation to supply the energy needed to excite reacting molecules, and sunlight is the usual natural…
Correct answer: Sunlight- A. Data insufficient to calculate
- B. 0.5
- C. 0.425
- D. 0.875
Explanation: After three half-lives, the unreacted fraction is (1/2)^3 = 1/8. Hence the conversion is 1 − 1/8 = 7/8 = 0.875.
Correct answer: 0.875- A. All A., B. and C.
- B. Is the maximum feed rate per unit volume of reactor for a given conversion
- C. Is a measure of the ease of the reaction
- D. Describes the extensive operating characteristics of a tubular flow reactor
Explanation: Space velocity is the feed volumetric rate divided by reactor volume, so it indicates how rapidly a reactor volume of feed is processed.
Correct answer: All A., B. and C.- A. Less than
- B. Equal to or more than
- C. More than
- D. Equal to
Explanation: Reaction occurs when molecular energy reaches or exceeds the activation-energy barrier.
Correct answer: Equal to or more than309. For a _____________ order reaction, the units of rate constant and rate of reaction are the same ?
- A. Second
- B. First
- C. Zero
- D. Fractional
Explanation: For a zero-order reaction, the rate is -rA = k, so the rate constant and reaction rate have identical units.
Correct answer: Zero- A. 60
- B. 75
- C. 90
- D. 100
Explanation: For the first CSTR, X = kτ/(1 + kτ) = 0.5, giving kτ = 1. A second identical CSTR leaves CA/CA0 = 1/(1+kτ)^2 = 1/4, so the total…
Correct answer: 75- A. L √(K/D1)
- B. ∞
- C. 1
- D. 1/[L√(K/D1)]
Explanation: When the Thiele modulus is large, diffusion strongly limits the reaction and only a thin region of catalyst is effectively used.
Correct answer: 1/[L√(K/D1)]- A. 1.0 to 10-8
- B. 1.1 to 102
- C. 0.1 to 0.9
- D. None of these
Explanation: The steric factor accounts for the fraction of collisions having suitable molecular orientation and is usually much less than unity, with…
Correct answer: 1.0 to 10-8- A. k/2
- B. ln k/2
- C. ln 2/k
- D. ln 0.5/k
Explanation: For a first-order irreversible reaction, CA/CA0 = e^-kt. At half-life CA/CA0 = 1/2, so kt = ln 2 and t1/2 = ln 2/k.
Correct answer: ln 2/k- A. Be more in CSTR than in PFR
- B. Depend on the temperature
- C. Be same in both cases
- D. Be more in PFR than in CSTR
Explanation: For a first-order reaction, a PFR gives the highest conversion for a specified volume and flow rate because every fluid element…
Correct answer: Be more in PFR than in CSTR- A. None of the above
- B. A step function
- C. A ramp function
- D. A Dirac delta function
Explanation: An ideal CSTR has an exponential exit age distribution, E(t) = (1/τ)e^(-t/τ), for t ≥ 0.
Correct answer: None of the above- A. May be lateral mixing of fluid
- B. Both A. and B.
- C. Should not be any mixing along the flow path
- D. Neither A. nor B.
Explanation: The ideal PFR permits complete lateral or radial mixing but has no axial mixing between fluid elements moving along the reactor.
Correct answer: Both A. and B.- A. 0
- B. 1
- C. 2
- D. 3
Explanation: Doubling concentration changes the rate by 2^n. Since the rate becomes four times larger, 2^n = 4 = 2^2, giving a second-order dependence…
Correct answer: 2- A. Temperature and pressure only
- B. Temperature and composition only
- C. Pressure and composition only
- D. All temperature, pressure and composition
Explanation: A homogeneous reaction rate can depend on composition through concentrations or activities, on temperature through the rate constant, and…
Correct answer: All temperature, pressure and composition- A. Is always greater for plug-flow reactor than for the single CSTR of the same volume
- B. Both A. and C. hold good
- C. Decreases with increasing conversion
- D. Statement in A. is wrong
Explanation: For a consecutive reaction in which an intermediate is the desired product, its relative yield generally falls as conversion increases…
Correct answer: Both A. and C. hold good- A. One of the reactants acts as a catalyst
- B. Catalysts have very high selectivity
- C. One of the products acts as a catalyst
- D. No catalyst is used
Explanation: In an autocatalytic reaction, a product formed by the reaction accelerates the same reaction, creating self-catalysis.
Correct answer: One of the products acts as a catalyst