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 178 of 350
- A. Time
- B. Temperature
- C. Concentration
- D. All A., B. & C.
Explanation: Conversion can be related to time through reactor operation, to temperature through the rate constant, and to concentration through the…
Correct answer: All A., B. & C.- A. Bubble
- B. Spray
- C. Tray
- D. Packed
Explanation: A bubble column retains a large continuous liquid phase while gas bubbles pass through it, giving high liquid hold-up for gas-liquid…
Correct answer: Bubble- A. Surface area
- B. Both B. & C.
- C. Pore volume
- D. Porosity
Explanation: Helium pycnometry determines the solid or skeletal volume, while mercury intrusion measures pore volume; together they allow catalyst…
Correct answer: Both B. & C.- A. Data in insufficient; can't be predicted
- B. Decrease
- C. Remain same
- D. Increase
Explanation: For an irreversible reaction in a plug-flow reactor, a longer space time gives the reactants more time to react.
Correct answer: Increase- A. Free energy of activation is higher
- B. Free energy of activation is lower
- C. Entropy changes
- D. Initial concentration of the reactants remains constant
Explanation: At a fixed temperature, a larger free energy of activation produces a smaller rate constant through the Arrhenius or Eyring relationship.
Correct answer: Free energy of activation is higher- A. Axial dispersion
- B. Flat velocity profile
- C. Uniform mixing
- D. None of these
Explanation: An ideal plug-flow reactor assumes no axial mixing and a uniform, flat velocity profile across the cross-section.
Correct answer: Flat velocity profile- A. 0
- B. 1
- C. 2
- D. 3
Explanation: For a zero-order reaction, the half-life is t1/2 = CA0/(2k), so doubling the initial concentration doubles the half-life.
Correct answer: 0- A. Room
- B. Lowest possible
- C. Intermediate
- D. Highest possible
Explanation: An endothermic reaction absorbs heat, so increasing temperature increases its equilibrium constant and generally raises the equilibrium…
Correct answer: Highest possible- A. Five reactor volumes of feed (at specified conditions) are being fed into the reactor per hour
- B. After every 5 hours, reactor is being filled with the feed
- C. Cent per cent conversion can be achieved in at least 5 hours
- D. A fixed conversion of a given batch of feed takes 5 hours
Explanation: Space velocity is the feed volumetric flow rate divided by reactor volume, with both measured at specified reference conditions.
Correct answer: Five reactor volumes of feed (at specified conditions) are being fed into the reactor per hour- A. 400
- B. 500
- C. 600
- D. 1000
Explanation: The heat released is 0.02 kmol/s × 0.20 × 50,000 kJ/kmol = 200 kJ/s, while the heat-capacity flow is 0.02 × 100 = 2 kJ/(s·K).
Correct answer: 600- A. Film diffusion
- B. Diffusion through ash layer
- C. Either A., B. or C.
- D. Chemical reaction
Explanation: For the surface-reaction-controlled shrinking-particle model, the time for a specified conversion is proportional to particle diameter.
Correct answer: Chemical reaction- A. 8
- B. 12
- C. 16
- D. 32
Explanation: The temperature rises by 40°C, corresponding to four 10°C intervals. Doubling at each interval gives 2⁴ = 16 times the original rate.
Correct answer: 163553. Which of the following resistances is not involved in a gas phase catalytic (gas-solid) reaction ?
- A. Gas film and pore surface diffusion resistances for reactants
- B. Ash resistance
- C. Surface phenomenon resistance
- D. Gas film and pore surface diffusion resistances for products
Explanation: A gas-solid catalytic reaction may involve gas-film transfer, pore diffusion, and surface reaction, but it does not form an ash layer.
Correct answer: Ash resistance- A. Always irreversible
- B. Mostly irreversible
- C. Insensitive to temperature changes
- D. Highly temperature sensitive
Explanation: From the Arrhenius equation, a smaller activation energy makes the rate constant change less when temperature changes.
Correct answer: Insensitive to temperature changes- A. 4
- B. 8
- C. 12
- D. 16
Explanation: A 75% conversion leaves 25% of the liquid, or one-fourth of the original amount.
Correct answer: 16- A. Uniformity of temperature
- B. Comparatively smaller equipment
- C. Very small pressure drop
- D. Absence of continuous catalyst regeneration facility
Explanation: Fluidized particles mix vigorously and provide excellent heat transfer, giving nearly uniform temperature throughout the bed.
Correct answer: Uniformity of temperature- A. None of these
- B. Increases with increase of pressure of reactants for all reactions
- C. Decreases with increase of reactant concentration
- D. Decreases with increase in temperature
Explanation: Reaction velocity generally increases with temperature, while pressure does not increase the rate for every reaction and concentration…
Correct answer: None of these- A. Converts N2 and H2 into NH3
- B. Is non-catalytic
- C. Converts CO to CO2 with steam
- D. Is highly exothermic
Explanation: The water-gas shift reaction converts carbon monoxide with steam into carbon dioxide and hydrogen: CO + H2O ⇌ CO2 + H2.
Correct answer: Converts CO to CO2 with steam- A. 1/(1 + k2 . CA0 . t)
- B. (k2 . CA0 . t)/ (1 + k2 . CA0 . t)2
- C. (k2 . CA0 . t)2/ (1 + k2 . CA0 . t)
- D. (k2 . CA0 . t)/ (1 + k2 . CA0 . t)
Explanation: For a constant-volume batch reaction with rate k2CA², integration gives 1/(1 − X) = 1 + k2CA0t. Rearranging yields X = k2CA0t/(1 + k2CA0t).
Correct answer: (k2 . CA0 . t)/ (1 + k2 . CA0 . t)- A. 7-10 %
- B. 2-5 %
- C. 12-15 %
- D. 20-25 %
Explanation: The contact process commonly uses a gas feed containing about 7–10% SO2, with oxygen and nitrogen making up most of the remainder.
Correct answer: 7-10 %