All Free Chemical Engineering MCQs with Answers

• A. Increase in initial concentration of A
• B. Decrease of temperature
• C. Increase of temperature
• D. Decrease in initial concentration of A

Explanation: When E1 is greater than E2, the first reaction rate increases more sharply with temperature than the subsequent reaction, improving the…

• A. Pore volume
• B. Solid density
• C. Porosity
• D. All A., B., & C.

Explanation: Helium measures the volume of the solid framework because it penetrates accessible pores, while mercury determines the pore volume it…

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

Explanation: A tubular flow reactor is compact and has no moving agitator or large vessel internals, making it suitable for continuous gas-phase…

• A. Half of the space time of a reaction
• B. The time required to reduce the concentration of the reacting substance to half its initial value
• C. Half of the residence time of a reaction
• D. None of these

Explanation: Half-life is defined as the time required for the concentration of a reactant to fall to one-half of its initial value.

• A. Depends upon the flow rate of inlet stream
• B. Is different than that in the reactor
• C. Is same as that in the reactor
• D. None of these

Explanation: For an ideal continuous stirred-tank reactor, perfect mixing makes the concentration uniform throughout the reactor.

• A. None of these
• B. Static steady
• C. Dynamic unsteady
• D. Dynamic steady

Explanation: At equilibrium, the forward and reverse reactions continue at equal rates, so the macroscopic composition remains constant while molecular…

• A. 7
• B. 6
• C. 3
• D. 7/3

Explanation: For a first-order reaction in a mixed-flow reactor, V = Q(Cin − Cout)/(kCout).

• A. Whole surface of the catalyst does not have the same activity for adsorption and there is
• B. attraction between the adsorbed molecule
• C. Whole surface of the catalyst is essentially uniform and the adsorbed molecule has no effect
• D. on the rate of adsorption per site
• E. All the adsorption does not take place by the same mechanism
• F. Extent of adsorption is more than one complete monomolecular layer on the surface

Explanation: Langmuir theory assumes a uniform surface with identical adsorption sites, no interaction between adsorbed molecules, and formation of…

• A. Activation energy
• B. Normal energy of reactants
• C. Sum of A. & B.
• D. Neither A. nor B.

Explanation: Threshold energy is the minimum energy required for reactants to reach the activated state, so it equals the normal reactant energy plus…

• A. CA (K1 + K2)
• B. CA (K1 + K2)/2
• C. CA . K1/2
• D. CA . K2/2

Explanation: For parallel elementary reactions, the disappearance rates from the separate paths add: -rX = k1CX + k2CX = CX(k1 + k2).

• A. Both conversion as well as concentration are same
• B. Conversion in both will be the same but concentrations will be different
• C. Both the conversion as well as concentrations will be different
• D. None of these

Explanation: For a first-order reaction, the mole balance gives dNA/dt = -kNA, so the fractional conversion after a given time is independent of…

• A. Fluidised bed reactor
• B. Fixed bed reactor
• C. Moving bed reactor
• D. None of these

Explanation: Industrial calcination of limestone and dolomite is commonly performed in moving or rotary kilns, where solids progress through the heated…

• A. ∝ CA
• B. ∝ 1/CA
• C. Independent of temperature
• D. None of these

Explanation: A zero-order rate is independent of reactant concentration, but none of the listed statements says this.

• A. Molar concentration of the reactants
• B. Volume of the reaction vessel
• C. Nature of the reactants
• D. Equilibrium constant

Explanation: The law of mass action relates reaction rate to the active masses, commonly represented by the molar concentrations, of the reacting…

• A. Zeroth order
• B. Third order
• C. Second order
• D. First order

Explanation: Doubling X doubles the rate, so X has order 1; doubling Y quadruples it, so Y has order 2.

• A. Remain unaffected
• B. Decreases
• C. Increases
• D. Unpredictable from the data

Explanation: For a gas-phase equilibrium reaction producing fewer moles, increasing pressure shifts equilibrium toward the products side.

• A. 1
• B. 2
• C. 3
• D. 4

Explanation: Let the rate be proportional to A^a B^b C^c. Doubling B gives b = 1, doubling A and B together gives a + b = 1 so a = 0, and doubling B…

• A. rA = rB
• B. rA = -rB
• C. rA = 2rB
• D. rA = rB/2

Explanation: The net stoichiometric coefficient of A is −1, while that of B is +1 because B is both consumed and produced, with one net mole formed.

• A. Greater than
• B. Smaller than
• C. Equal to
• D. Unpredictable from the data

Explanation: For positive-order reactions, the reaction rate generally falls as reactants are consumed, so a PFR uses the high reactant concentration…

• A. Active at cryogenic temperatures only
• B. Prohibitively costly
• C. Proteinous in nature
• D. Active at very high temperature only

Explanation: In conventional chemical-engineering usage, organic biological catalysts refer mainly to enzymes, which are proteinaceous molecules.