All Free Chemical Engineering MCQs with Answers
Every Chemical Engineering question in the bank, across all chapters, each with the correct answer and a written explanation. Free and unlimited, with no account needed.
6,983 questions · page 181 of 350
- A. Non-Homogeneous
- B. Homogeneous
- C. Heterogeneous
- D. Non-Heterogeneous
Explanation: Thermal cracking of gas oil proceeds without a solid catalyst and is treated as a homogeneous gas-phase radical reaction.
Correct answer: Homogeneous- A. Moles for med/(surface of catalyst) (time)
- B. Moles formed/volume of reactor) (time)
- C. None of these
- D. Mole formed/volume of catalyst) (time)
Explanation: Reaction rate may be expressed per reactor volume, catalyst volume, or catalyst surface area, provided the basis is stated.
Correct answer: None of these- A. Consecutive
- B. Third order
- C. Zero order
- D. None of these
Explanation: In a zero-order reaction, the rate is k and does not depend on reactant concentration.
Correct answer: Zero order- A. Poor product quality control
- B. High labour and handling cost
- C. High shutdown time requirement for emptying, cleaning and refilling
- D. All A., B. and C.
Explanation: Batch operation can cause batch-to-batch quality variation and requires substantial labour, handling, and downtime for emptying, cleaning…
Correct answer: All A., B. and C.- A. Variation in extent of reaction and properties of the reaction mixture with time
- B. Constant residence time
- C. Variation in reactor volume
- D. Very low conversion
Explanation: In a batch reactor, reactants are charged initially and their concentrations, conversion, and other mixture properties change with time.
Correct answer: Variation in extent of reaction and properties of the reaction mixture with time- A. k. t = ln a/(a - x)
- B. k. t = x/a (a - x)
- C. k. t = ln (a - x)/a
- D. k. t = ln a (a - x)/x
Explanation: For a first-order reaction, integration of −dC/dt = kC from C = a to C = a−x gives kt = ln[a/(a−x)].
Correct answer: k. t = ln a/(a - x)- A. Less than
- B. Equal to
- C. More than
- D. Equal to or more than
Explanation: Molecules must have energy at least equal to the activation energy to cross the reaction-energy barrier, so the condition is equal to or…
Correct answer: Equal to or more than- A. Diffusion through ash layer
- B. Film diffusion
- C. Chemical reaction
- D. Either A., B. or C.
Explanation: For the shrinking-core model, resistance through the ash layer gives a characteristic time proportional to the square of particle…
Correct answer: Diffusion through ash layer- 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 than3617. 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