All Free Chemical Engineering MCQs with Answers

• A. Same as that of rate constant
• B. Same as that of activation energy
• C. Dimensionless
• D. None of these

Explanation: In k = A exp(-E/RT), the exponential is dimensionless, so A must carry the same units as k.

• A. Operational yield
• B. Selectivity
• C. Relative yield
• D. None of these

Explanation: Selectivity compares the amount of desired product, or reactant consumed to form it, with the corresponding amount forming unwanted…

• A. For CSTR
• B. For large diameter tubular reactor
• C. For narrow diameter tubular reactor
• D. When the density of the reaction mixture is constant

Explanation: Space time is based on reactor volume divided by inlet volumetric flow, whereas mean residence time uses the actual flow within the…

• A. All A., B. and C.
• B. Temperature of the system
• C. Pressure of the system
• D. Composition of the component only

Explanation: Reaction rate is affected by composition through concentrations or partial pressures and by temperature through the rate constant…

• A. (1/k) ln C/C0
• B. (1/k) ln C0/C
• C. k ln C0/C
• D. k ln C/C0

Explanation: For a first-order reaction in a constant-density plug flow reactor, integrating dC/dτ = -kC gives τ = (1/k) ln(C0/C).

• A. 3 hours
• B. The time required to process one reactor volume of feed (measured at specified conditions) is
• C. Three reactor volumes of feed can be processed every hour
• D. It takes three hours to dump the entire volume of the reactor with feed
• E. Conversion is cent per cent after three hours

Explanation: Space time is the reactor volume divided by the volumetric feed rate, so it represents the time needed to process one reactor volume of…

• A. 2/3 kW
• B. 1 kW
• C. 5/3 kW
• D. 4 kW

Explanation: The heat released is qCA0XA|ΔH| = (10⁻³)(5)(0.5)(40,000) kJ/min = 100 kJ/min, or 1.67 kW.

• A. t ∝ 1/an
• B. t ∝ 1/an - 1
• C. t ∝ 1/an + 1
• D. t ∝ an

Explanation: For a fixed fractional conversion in an nth-order batch reaction, the time scales as the inverse of the initial concentration raised to…

• A. High pressure batch reactor
• B. Atmospheric pressure tank reactor
• C. High pressure tubular reactor
• D. Atmospheric pressure CSTR

Explanation: An autoclave is a pressure vessel commonly used for batch processing under elevated pressure, often also at elevated temperature.

• A. P.F. reactors in series
• B. CSTR in series
• C. CSTR followed by P.F. reactor
• D. P.F. reactor followed by CSTR

Explanation: An autocatalytic reaction is slow at the feed inlet because little product catalyst is present, so a CSTR first builds up product…

• A. Reaction kinetics for single particle
• B. Size distribution of solids being treated
• C. Flow patterns of solids and fluid in the reactor
• D. All A., B. and C.

Explanation: Fluid-solid reactor design must account for intrinsic particle kinetics, the distribution of solid sizes, and the contacting or flow…

• A. Activated complex theory
• B. Collision theory
• C. Thermodynamics
• D. None of these

Explanation: Activated complex theory explains catalysis by showing that a catalyst provides an alternative reaction pathway with a lower activation…

• A. 0
• B. < 0.5
• C. ∞
• D. > 0.5

Explanation: A small Thiele modulus indicates that the reaction is not fast enough for a significant concentration gradient inside the pores; pore…

• A. Catalyst
• B. Temperature
• C. Number of molecules of reactants taking part in a reaction
• D. Reactants concentration

Explanation: Reaction rate is directly affected by temperature, reactant concentration and catalysts, but the mere number of molecules shown in the…

• A. Equilibrium constant is 1
• B. Conversion of the reactant at equilibrium condition is zero
• C. All A., B. and C.
• D. Reactant concentration at equilibrium condition is zero

Explanation: An irreversible reaction can be treated as a reversible reaction whose equilibrium lies completely toward products, so the reactant…

• A. Both A. and B.
• B. Distribution of reaction products
• C. Size requirement
• D. Neither A. nor B.

Explanation: For multiple reactions, mixing and residence-time patterns determine how much each reaction proceeds, affecting both product distribution…

• A. Does not initiate the reaction
• B. Reduces the value of equilibrium constant
• C. Retards the rate of reaction
• D. All A., B. and C.

Explanation: A negative catalyst, or inhibitor, lowers the reaction rate by increasing the effective resistance to reaction.

• A. Threshold
• B. Potential
• C. Binding
• D. Activation

Explanation: Activation energy is the minimum excess energy reactant molecules must acquire to reach the activated state and undergo reaction.

• A. One
• B. Zero
• C. Two
• D. Three

Explanation: For a first-order reaction, the half-life is t₁/₂ = 0.693/k and contains no initial concentration term.

• A. Suitable for gas phase reactions
• B. Same as ideal stirred tank reactor
• C. Same as plug flow reactor (PFR)
• D. Ideal at very low conversion

Explanation: A back-mix reactor continuously mixes incoming material with reactor contents, making its composition uniform throughout.