What is the primary advantage of using a plug flow reactor (PFR) over a continuous stirred tank reactor (CSTR) for reactions with activation energy greater than 50 kJ/mol?

The correct answer is C: Higher conversion at same residence time due to increasing temperature profile with reaction progress. For high activation energy reactions, the increasing temperature from adiabatic exothermic reactions in PFR increases reaction rate progressively, improving conversion over CSTR where temperature is uniform and lower.

In a constant volume process, the heat added to the system equals:

The correct answer is A: Change in internal energy (ΔU). For constant volume: W = 0, so Q = ΔU from first law (ΔU = Q - W). This is isochoric process where all heat goes to internal energy change.

In a counter-current liquid-liquid extraction process, the extraction becomes more efficient when the difference between equilibrium and operating lines increases. What does this signify?

The correct answer is B: Increased driving force for mass transfer. A larger gap between the operating line and equilibrium line indicates greater concentration difference, which increases the driving force (ΔC) for mass transfer, leading to higher transfer rates.

The relative roughness of a pipe is defined as:

The correct answer is B: Ratio of absolute roughness to pipe diameter. Relative roughness ε/D = (absolute roughness)/(pipe diameter). This dimensionless parameter determines flow behavior in the Moody chart for turbulent flow calculations.

Which of the following is the correct definition of mass transfer coefficient in a binary diffusion system?

The correct answer is A: Rate of mass transfer per unit area per unit concentration difference. Mass transfer coefficient (k) is defined as the rate of mass transfer per unit interfacial area per unit concentration difference, with units of length/time.

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Chemical Engineering
Chemical Reaction Engineering

Process design, thermodynamics, reactions

26 Q 5 Topics Take Mock Test

Difficulty: All Easy Medium Hard 21–26 of 26

Topics in Chemical Engineering

All Mass Transfer 100 Heat Transfer 100 Fluid Mechanics 100 Chemical Reaction Engineering 100 Thermodynamics 97

Q.21 Hard Chemical Reaction Engineering

In desorption-limited catalytic reactions, which step determines the overall reaction rate?

A Reactant adsorption on catalyst surface

B Surface reaction between adsorbed species

C Product desorption from catalyst surface

D Diffusion of reactant to catalyst surface

Correct Answer: C. Product desorption from catalyst surface

EXPLANATION

When desorption is the rate-limiting step, products stick to the catalyst and their slow removal prevents further reaction cycles, controlling overall rate

Test

Q.22 Hard Chemical Reaction Engineering

For consecutive reactions A→B→C, the concentration of intermediate B is maximum at time t_max. This time depends on:

A Only k₁ and k₂

B Only initial concentration of A

C Both k₁, k₂ and initial concentration of A

D Temperature only

Correct Answer: A. Only k₁ and k₂

EXPLANATION

t_max = ln(k₂/k₁)/(k₂-k₁), depends only on rate constants, independent of [A]₀

Test

Q.23 Hard Chemical Reaction Engineering

Which approximation is used in steady-state kinetics for enzyme reactions?

A Quasi-equilibrium approximation

B Steady-state approximation for ES complex

C Pre-equilibrium approximation

D Both B and C

Correct Answer: D. Both B and C

EXPLANATION

Both steady-state (d[ES]/dt = 0) and pre-equilibrium approximations are used in Michaelis-Menten derivation

Test

Q.24 Hard Chemical Reaction Engineering

For a reaction with E_a = 50 kJ/mol, if temperature is increased from 300K to 400K, by what factor does rate constant increase? (R = 8.314 J/mol·K)

A 3.2 times

B 8.5 times

C 15.8 times

D 22.3 times

Correct Answer: C. 15.8 times

EXPLANATION

ln(k₂/k₁) = (50000/8.314)[1/300 - 1/400] = 2.76; k₂/k₁ = e^2.76 ≈ 15.8

Test

Q.25 Hard Chemical Reaction Engineering

Which reactor configuration gives maximum yield for a series reaction A→B→C where k₁ >> k₂?

A Batch reactor with optimized residence time

B CSTR operating at high temperature

C PFR with very high conversion

D Recycle reactor

Correct Answer: A. Batch reactor with optimized residence time

EXPLANATION

For A→B→C series, batch allows control of residence time to maximize intermediate B before it converts to C

Test

Q.26 Hard Chemical Reaction Engineering

What is the activation energy for a reaction if its rate constant doubles when temperature increases from 300K to 310K?

A 45.6 kJ/mol

B 52.8 kJ/mol

C 60.2 kJ/mol

D 72.5 kJ/mol

Correct Answer: B. 52.8 kJ/mol

EXPLANATION

Using Arrhenius equation: ln(k₂/k₁) = (Eₐ/R)[1/T₁ - 1/T₂]; ln(2) = (Eₐ/8.314)[1/300 - 1/310]; Eₐ ≈ 52.8 kJ/mol

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