Free Chemical Reaction Engineering MCQs with Answers

• 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.

• 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).

• 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.

• 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.

• 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.

• 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.

• A. 4
• B. 8
• C. 12
• D. 16

Explanation: A 75% conversion leaves 25% of the liquid, or one-fourth of the original amount.

• 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.

• 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…

• 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.

• 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).

• 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.

• A. Endothermic
• B. Exothermic
• C. Biochemical
• D. Photochemical

Explanation: Combustion is the oxidation of organic material by oxygen, and it releases heat because the products are at a lower energy level than the…

• A. Collision theory and activated complex theory
• B. Chain reaction theory
• C. None of these
• D. Radiation hypothesis

Explanation: Collision theory, activated complex theory, chain reaction theory, and radiation hypothesis are all used to explain reaction behaviour or…

• A. 100%
• B. 95%
• C. 75%
• D. 20%

Explanation: The carbon consumed is 16.5/44 + 2.8/28 = 0.475 mol, while the initial carbon is 6/12 = 0.5 mol.

• A. More when they are connected in series
• B. Less when they are connected in series
• C. More when they are connected in parallel
• D. Same whether they are connected in series or in parallel

Explanation: For a first-order reaction, equal CSTRs in series give successive concentration reductions, producing a higher overall conversion than…

• A. Larger reactors have more space time compared to smaller ones
• B. Space time for parallel lines is different
• C. Space time for each parallel line is same
• D. None of these

Explanation: Parallel reactors perform optimally when each line has the same space time, provided the reactors have the same kinetics and operating…

• A. 5/4
• B. 7/4
• C. 5/2
• D. 7/2

Explanation: If rate is proportional to A^mB^n, doubling A gives 2^m = 2.82, so m is approximately 1.5; trebling B gives 3^n = 9, so n = 2.

• A. Slower rate of reaction
• B. Higher rate of reaction
• C. Higher equilibrium conversion
• D. Both B. and C.

Explanation: A higher Gibbs free energy of activation means a smaller rate constant according to transition-state theory, so fewer molecules cross the…

• A. When the data are scattered
• B. Both A. and B.
• C. For testing specific mechanisms with simple rate expressions
• D. None of these

Explanation: The integral method compares concentration-time data with integrated forms of proposed rate laws, making it useful for testing simple…