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 175 of 350
- A. Space time is equivalent to holding time for constant density systems
- B. Composition throughout the reactor remains same
- C. All A., B. and C.
- D. Exit stream has the same composition as the fluid within the reactor
Explanation: In an ideal mixed reactor, perfect mixing makes the composition uniform and equal to the exit composition.
Correct answer: All A., B. and C.- A. Large catalyst particle size
- B. An active surface of the catalyst
- C. Small pore diameter
- D. All A., B. and C.
Explanation: Diffusion becomes more important when particles are larger, pores are narrower, or the catalyst is more active and consumes reactant…
Correct answer: All A., B. and C.- A. 3
- B. 1
- C. 1/3
- D. 32
Explanation: Space time is reactor volume divided by the inlet volumetric flow rate: τ = V/v₀ = 3 L/(1 L s⁻¹) = 3 s. The correct option is therefore b.
Correct answer: 3- A. Increases
- B. Remain constant
- C. Decreases
- D. Unpredictable
Explanation: For a first-order batch reaction, the integrated relation is −ln(1 − X) = kt, so conversion at a fixed time depends on k and t, not on the…
Correct answer: Remain constant- A. 2 & 2
- B. 11 & 2
- C. 2 & 1
- D. 1 & 1
Explanation: Methyl acetate hydrolysis is bimolecular because ester and water participate in the overall reaction, giving molecularity 2.
Correct answer: 2 & 1- A. K α e-E/RT
- B. K α eE/RT
- C. K α T . e-E/RT
- D. K α √T . e-E/RT
Explanation: Arrhenius behaviour is k = A exp(-E/RT), so the rate constant increases with temperature because the negative exponent becomes less…
Correct answer: K α e-E/RT- A. Directly proportional to
- B. Independent of
- C. Inversely proportional to
- D. None of these
Explanation: For a first-order reaction, t₁/₂ = 0.693/k, which contains no initial concentration term.
Correct answer: Independent of- A. Decrease
- B. Increase
- C. No change
- D. Either A. or B., depends on the type of reaction
Explanation: For an ideal CSTR, the recycle stream has the same composition as the reactor outlet, so its effects cancel in the overall material…
Correct answer: No change- A. Semi-batch
- B. Tubular
- C. Batch
- D. Back-mix
Explanation: A back-mix reactor, or ideal CSTR, is perfectly mixed, so the composition is uniform throughout the vessel and equals the outlet…
Correct answer: Back-mix- A. Activation energy
- B. Equilibrium constant
- C. Heat of reaction
- D. None of these
Explanation: A catalyst provides an alternative reaction pathway with a lower activation energy, increasing the forward and reverse rates.
Correct answer: Activation energy- A. Consecutive
- B. Parallel
- C. Elementary
- D. None of these
Explanation: Chlorination occurs through successive substitutions: benzene forms chlorobenzene, then dichlorobenzene, and finally trichlorobenzene.
Correct answer: Consecutive- A. N2 + O2 ⇌ 2NO
- B. PCl3 + Cl2 ⇌ PCl5
- C. N + 3H2 ⇌ 2NH3
- D. 2SO2 + O2 ⇌ 2SO3
Explanation: For N₂ + O₂ ⇌ 2NO, the total number of gas moles is unchanged, so pressure does not shift the equilibrium yield.
Correct answer: N2 + O2 ⇌ 2NO- A. Continuously increases
- B. Continuously decreases
- C. Passes through a minimum
- D. Passes through a maximum
Explanation: At first, the exothermic reaction accelerates because the adiabatic temperature rises, but as conversion increases the reversible reaction…
Correct answer: Passes through a maximum- A. Very temperature sensitive
- B. Temperature insensitive
- C. Always irreversible
- D. Always reversible
Explanation: From the Arrhenius equation, a high activation energy makes the rate constant change sharply with temperature.
Correct answer: Very temperature sensitive3495. For a mixed flow reactor operating at steady state, the rate of reaction is given by______________?
- A. (FA0/V) - (dCA/dt)
- B. (FA0/V) XA
- C. (FA0/V) + (dCA/dt)
- D. -(dCA/dt)
Explanation: For a steady-state mixed reactor, the exit concentration equals the reactor concentration, and the material balance gives -rA = FA0XA/V.
Correct answer: (FA0/V) XA- A. Remain same
- B. Decreases
- C. Increases
- D. Increases linearly
Explanation: For a positive-order reaction, a mixed reactor evaluates the rate at the lowest concentration, the exit concentration, while a plug-flow…
Correct answer: Increases- A. Zero order & K1/K2
- B. Zero order & K1
- C. First order & K1
- D. First order & K1/K2
Explanation: When K2Cx is much greater than one, the denominator is approximately K2Cx, so -rx becomes (K1/K2), independent of concentration.
Correct answer: Zero order & K1/K2- A. ∞
- B. 0
- C. 1
- D. -1
Explanation: The dispersion number measures axial mixing relative to plug flow. Ideal plug flow has no axial dispersion, so its dispersion number is…
Correct answer: 0- A. K α e-E/RT
- B. K α eE/RT
- C. K α T . e-E/RT
- D. K α √T . e-E/RT
Explanation: Transition state theory includes a frequency term proportional to temperature, giving k proportional to T exp(-E/RT) in the simplified…
Correct answer: K α T . e-E/RT- A. exp (-E/RT)
- B. exp (-E/2RT)
- C. √T
- D. Tm exp (-E/RT)
Explanation: Collision theory combines the collision-frequency factor, commonly represented by T^m, with the fraction of collisions having enough…
Correct answer: Tm exp (-E/RT)