All Free Chemical Engineering MCQs with Answers

• 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.

• A. Solutions
• B. Liquid state only
• C. Solid state only
• D. Any state

Explanation: Ionic reactions involve ions moving and reacting in a medium, so they are commonly studied in aqueous or other liquid solutions.

• A. Increases
• B. Decreases
• C. Remain unaffected
• D. Increases linearly with temperature

Explanation: An endothermic reaction absorbs heat, so lowering the temperature shifts equilibrium toward the reactants according to Le Chatelier’s…

• A. Hydrogenation of oils
• B. Alkylation of hydrocarbons
• C. Gas phase oxidation of SO2 in chamber process
• D. None of these

Explanation: Sulphuric acid provides acidic sites that promote the formation of alkylated hydrocarbons from an olefin and an isoparaffin.

• A. Most suitable for a second order reaction
• B. Most suitable for a reversible reaction
• C. Completely self-supporting in its thermal energy requirements
• D. Isothermal in nature

Explanation: An autothermal reactor obtains the heat required for an endothermic reaction, or removes the heat generated by an exothermic reaction…

• A. Increasing the concentration of one of the reactants
• B. None of these
• C. Removal of at least one of the products at regular interval
• D. Increasing the concentration of one or more of the products

Explanation: Adding a product increases the reaction quotient, so the equilibrium shifts toward reactants to consume some of that product.

• A. -rA = (k . PA . PB)/(1 + KAPB + KBPB . KPPP)
• B. -rA = (k . PA
• C. 2 - k1PP)/(1 + KAPA + KPPP)
• D. -rA = (k . PA . PB)/(1 + KAPA + KPPP)
• E. -rA = (k . PA . PB)/(1 + KAPA)

Explanation: For the Rideal mechanism, one reactant is adsorbed while the other reacts directly from the gas phase, giving a rate proportional to PA…

• A. Batch reactor is preferred over a single CSTR for high yield
• B. Tubular reactor is preferred over a single CSTR for high yield
• C. Both A. and B.
• D. Single CSTR is the most suitable

Explanation: When the desired reaction has the higher order, high reactant concentration improves its rate relative to the undesired reaction.

• A. Large reactor followed by smaller one
• B. Smaller reactor followed by larger one
• C. Data insufficient, can't be predicted
• D. Either of the arrangement A. or B. will give the same yield

Explanation: For a first-order reaction in CSTRs, the overall conversion depends on the sum of the reactor volumes divided by the flow rate, not on…

• A. 256
• B. 512
• C. 112
• D. 612

Explanation: The temperature rises by 90°C, which equals nine 10°C intervals. Doubling nine times gives 2^9 = 512, so the rate becomes 512 times its…

• A. > 1
• B. 1
• C. < 1
• D. 0

Explanation: With constant density, the volumetric flow rate does not change through the reactor, so space time V divided by flow rate equals the mean…

• A. Catalytic
• B. Photochemical
• C. Autocatalytic
• D. None of these

Explanation: A reaction is autocatalytic when one of its products catalyses the same reaction, causing the reaction rate to depend partly on product…

• A. None of these
• B. Useful volume of the tank
• C. Diameter of the reactor
• D. Time

Explanation: In a batch reactor, material is charged and then allowed to react without continuous feed or withdrawal, so time is the independent…