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 12 of 20
- A. Activation energy
- B. Normal energy of reactants
- C. Sum of A. & B.
- D. Neither A. nor B.
Explanation: Threshold energy is the minimum energy required for reactants to reach the activated state, so it equals the normal reactant energy plus…
Correct answer: Sum of A. & B.- A. CA (K1 + K2)
- B. CA (K1 + K2)/2
- C. CA . K1/2
- D. CA . K2/2
Explanation: For parallel elementary reactions, the disappearance rates from the separate paths add: -rX = k1CX + k2CX = CX(k1 + k2).
Correct answer: CA (K1 + K2)- A. Both conversion as well as concentration are same
- B. Conversion in both will be the same but concentrations will be different
- C. Both the conversion as well as concentrations will be different
- D. None of these
Explanation: For a first-order reaction, the mole balance gives dNA/dt = -kNA, so the fractional conversion after a given time is independent of…
Correct answer: Conversion in both will be the same but concentrations will be different224. Which of the following is used for calcination of limestone and dolomite in industrial practice?
- A. Fluidised bed reactor
- B. Fixed bed reactor
- C. Moving bed reactor
- D. None of these
Explanation: Industrial calcination of limestone and dolomite is commonly performed in moving or rotary kilns, where solids progress through the heated…
Correct answer: Moving bed reactor- A. ∝ CA
- B. ∝ 1/CA
- C. Independent of temperature
- D. None of these
Explanation: A zero-order rate is independent of reactant concentration, but none of the listed statements says this.
Correct answer: None of these- A. Molar concentration of the reactants
- B. Volume of the reaction vessel
- C. Nature of the reactants
- D. Equilibrium constant
Explanation: The law of mass action relates reaction rate to the active masses, commonly represented by the molar concentrations, of the reacting…
Correct answer: Molar concentration of the reactants- A. Zeroth order
- B. Third order
- C. Second order
- D. First order
Explanation: Doubling X doubles the rate, so X has order 1; doubling Y quadruples it, so Y has order 2.
Correct answer: Third order- A. Remain unaffected
- B. Decreases
- C. Increases
- D. Unpredictable from the data
Explanation: For a gas-phase equilibrium reaction producing fewer moles, increasing pressure shifts equilibrium toward the products side.
Correct answer: Increases- A. 1
- B. 2
- C. 3
- D. 4
Explanation: Let the rate be proportional to A^a B^b C^c. Doubling B gives b = 1, doubling A and B together gives a + b = 1 so a = 0, and doubling B…
Correct answer: 2- A. rA = rB
- B. rA = -rB
- C. rA = 2rB
- D. rA = rB/2
Explanation: The net stoichiometric coefficient of A is −1, while that of B is +1 because B is both consumed and produced, with one net mole formed.
Correct answer: rA = -rB- A. Greater than
- B. Smaller than
- C. Equal to
- D. Unpredictable from the data
Explanation: For positive-order reactions, the reaction rate generally falls as reactants are consumed, so a PFR uses the high reactant concentration…
Correct answer: Smaller than- A. Active at cryogenic temperatures only
- B. Prohibitively costly
- C. Proteinous in nature
- D. Active at very high temperature only
Explanation: In conventional chemical-engineering usage, organic biological catalysts refer mainly to enzymes, which are proteinaceous molecules.
Correct answer: Proteinous in nature- 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