All Free Chemical Engineering MCQs with Answers

• A. Equals
• B. Is smaller than
• C. Is greater than
• D. Can be either greater or smaller than (depends on the type of reaction)

Explanation: When the limiting reactant is completely consumed, the amount used as the basis for operational yield is the same stoichiometric reactant…

• A. Feed rate
• B. Reactor volume
• C. All A., B. and C.
• D. Extent of reaction

Explanation: Reactor performance balances connect the reaction rate with the feed rate and reactor volume, while the extent of reaction expresses the…

• A. There is no mixing in longitudinal direction
• B. Mixing takes place in radial direction
• C. There is a uniform velocity across the radius
• D. All A., B. and C.

Explanation: An ideal tubular-flow reactor has plug flow: no longitudinal or axial mixing, complete radial mixing, and a uniform velocity profile…

• A. Non-adiabatic
• B. Isothermal
• C. Adiabatic
• D. None of these

Explanation: An adiabatic reactor has no heat exchange, while an isothermal reactor maintains constant temperature.

• A. Decreases
• B. Increases
• C. Remain same
• D. Becomes infinite

Explanation: A catalyst provides an alternative pathway with lower activation energy, increasing the forward reaction rate constant at a given…

• A. Batch
• B. Tubular flow
• C. Stirred tank
• D. Fixed bed

Explanation: A stirred-tank reactor provides continuous mixing and effective heat removal, making it suitable for nearly isothermal liquid-phase…

• A. 8
• B. 1/8
• C. 16
• D. 1/16

Explanation: Reducing the reactor volume to one-fourth increases each gas concentration fourfold when the number of moles is unchanged.

• A. Pressure has no effect
• B. Backward reaction is favoured
• C. Forward reaction is favoured
• D. None of these

Explanation: The reaction has five total moles of gaseous reactants and five total moles of gaseous products.

• A. Pulse
• B. Both A. & B.
• C. Step
• D. Neither A. nor B.

Explanation: Both pulse and step changes are standard stimulus inputs in tracer-response studies.

• A. Reaction can be accomplished with small reactor
• B. Conversion can be obtained with a high feed rate
• C. Both A. and B.
• D. None of these

Explanation: Space velocity is feed rate per unit reactor volume, so a high value indicates a high throughput for a given reactor size.

• A. 1.6
• B. 2
• C. 2.24
• D. 2.5

Explanation: Arrhenius behavior gives k500/k400 = 2, while transition-state theory adds the temperature factor T500/T400 = 1.25.

• A. None of these
• B. Adsorption
• C. Desorption
• D. Surface chemical reaction

Explanation: Adsorption, surface reaction, and desorption are all chemical steps in the usual mechanism for a fluid-solid catalytic reaction.

• A. Be halved
• B. Remain the same
• C. Also be doubled
• D. Become one fourth

Explanation: At a fixed temperature, the equilibrium constant depends only on temperature and the reaction stoichiometry, not on the starting…

• A. Have very high selectivity
• B. Increase the activity of a catalyst
• C. Provide large surface area with a small amount of active material
• D. Inhibit catalyst poisoning

Explanation: A catalyst carrier or support disperses a relatively small amount of active material over a large porous surface.

• A. Slowest
• B. Fastest
• C. Intermediate
• D. Data insufficient; can't be predicted

Explanation: In the simplified consecutive-step model, the slowest step limits the overall reaction rate and is called the rate-determining step.

• A. Gas film diffusion
• B. Chemical reaction
• C. Ash diffusion
• D. None of these

Explanation: For a highly temperature-sensitive fluid-solid reaction, the chemical reaction step has the greatest temperature dependence and therefore…

• A. (1 + x)2
• B. (1 - x)
• C. (1 + x)
• D. (1 - x)2

Explanation: Taking one initial mole of N₂O₄, the undissociated amount is 1 − x and dissociation produces 2x moles of NO₂.

• A. And decreases that of backward reaction
• B. To a greater extent than that of the backward reaction
• C. Only
• D. And backward reaction equally

Explanation: A catalyst provides an alternative pathway and lowers the activation barriers for both forward and reverse reactions.

• A. Temperature
• B. Concentration of the reactant
• C. Concentration of the product
• D. Time

Explanation: For a given reaction, the rate constant is primarily a function of temperature through the Arrhenius equation.

• A. 0
• B. 1
• C. 2
• D. 3

Explanation: Equal times for reducing concentration by the same factor, from 100 to 50 and from 2 to 1, indicate a constant half-life.