Free Chemical Reaction Engineering MCQs with Answers

• A. 1.5 K
• B. 2.5 K
• C. 0.693/K
• D. 6.93 K

Explanation: For a first-order reaction, the half-life is independent of the initial concentration and is given by t₁/₂ = ln 2/k = 0.693/k.

• A. None of these
• B. Increases the activation energy
• C. Decreases the molecular collision diameter
• D. Decreases the energy barrier for reaction

Explanation: A catalyst provides an alternative reaction pathway with a lower activation-energy barrier, allowing more molecules to react per unit…

• A. k KAKB pApB / (1 + KApA + KBpB + KCpC)2
• B. k KAKB pApB / (1 + KApA + KBpB)
• C. k KAKB pApB / (1 + KApA + KBpB + KCpC)
• D. k KA pApB / (1 + KApA + KBpB)

Explanation: With competitive adsorption, the surface coverages of adsorbed A and B are proportional to K_Ap_A and K_Bp_B, while the vacant-site…

• A. 2
• B. 4
• C. 11
• D. 22

Explanation: For a second-order reaction, t = X/[kC_A0(1−X)]. Thus t₉₀/t₄₅ = [0.90/0.10]/[0.45/0.55] = 11, giving the required ratio.

• A. Accompanied with emission of light
• B. Catalysed by light
• C. Initiated by light
• D. All A., B. & C.

Explanation: A photochemical reaction is initiated when reactant molecules absorb light and acquire enough energy to react.

• A. Fixed
• B. Fluidised
• C. Fixed bed reactor followed by a fluidised
• D. Fluidised bed reactor followed by a fixed

Explanation: A fluidised bed provides effective heat removal and limits temperature rise in a highly exothermic reaction, while the following fixed bed…

• A. Is at the highest allowable temperature throughout
• B. Increases
• C. Decreases
• D. First increases and then decreases

Explanation: For an endothermic reversible reaction, increasing temperature generally increases both the reaction rate and the equilibrium conversion.

• A. Suitable for gas-phase reactions on commercial scale
• B. Suitable for liquid phase reactions involving small production rate
• C. Least expensive to operate for a given rate
• D. Most suitable for very large production rate

Explanation: Batch reactors are commonly used for liquid-phase products made at relatively small or moderate production rates, especially when…

• A. Third
• B. Second
• C. First
• D. Zero

Explanation: Radioactive decay is a first-order process because the decay rate is proportional to the amount of radioactive material remaining.

• A. Tank in series
• B. Dispersion
• C. Neither A. nor B.
• D. Both A. & B.

Explanation: Both the tanks-in-series model and the dispersion model describe non-ideal flow using one adjustable parameter, such as the number of…

• A. The energy of reacting molecules exceeds the activation energy by absorption of light
• B. It is an exothermic reaction
• C. It is a reversible reaction
• D. None of these

Explanation: Absorption of light supplies the reacting molecules with energy directly, often raising them above the activation-energy barrier.

• A. Achieving cent percent conversion of reactants into products
• B. Liquid phase reactions
• C. Large scale gaseous phase reactions
• D. Obtaining uniform polymerisation products in highly exothermic reactions

Explanation: Batch reactors are widely used for liquid-phase reactions because they offer flexible operation and can handle relatively small production…

• A. Is same as plug-flow reactor
• B. Employs mixing in axial direction only
• C. Is same as ideal stirred tank reactor
• D. Is most suitable for gas phase reaction

Explanation: Backmixing means that material leaving the reactor has the same composition as material throughout the vessel, which is the ideal…

• A. Chemical
• B. Physical
• C. Both A. and B.
• D. Neither A. nor B.

Explanation: Catalytic activity mainly depends on chemisorption, because chemical adsorption forms activated bonds between the reactant and the…

• A. Both forward and backward reactions will be exothermic
• B. Neither of the reactions will be endothermic
• C. endothermic
• D. The combination reaction will be exothermic, while the dissociation reaction will be
• E. The combination reaction will be endothermic, while the dissociation reaction will be
• F. exothermic

Explanation: The combination of A and B to form AB releases the heat that is absorbed when AB dissociates.

• A. 100
• B. 1000
• C. 10000
• D. 100000

Explanation: Physical adsorption involves weak van der Waals forces, so its heat is relatively low, commonly of the order of 1000 kcal per kg mole.

• A. Composition of reactant
• B. Pressure
• C. Temperature
• D. Heat and mass transfer effects

Explanation: When a heterogeneous reaction is very fast, the intrinsic surface reaction is no longer rate-controlling.

• A. All A., B. and C.
• B. Plot of products concentration with time is a straight line through the origin
• C. Products concentration increases linearly with time
• D. Half life period is directly proportion to the initial concentration of the reactants

Explanation: For a zero-order reaction, reactant concentration falls and product concentration rises linearly with time, while the half-life is…

• A. First
• B. Any
• C. Third
• D. Second

Explanation: Ideal plug-flow reactors in series behave as one plug-flow reactor whose total volume equals the sum of their volumes.

• A. Reaction rate is independent of the reactant's concentration
• B. Reactant's concentration is very high
• C. Reactant's concentration is very low
• D. Temperature is very high

Explanation: Enzymes are proteins whose structure is damaged or denatured at excessive temperature, causing loss of catalytic activity.