A throttle valve is used in a refrigeration cycle. This is an example of a(n) _____ process.

The correct answer is C: Adiabatic irreversible. Throttling is an adiabatic (Q=0) but irreversible process with no work done, causing entropy increase

For an exothermic reaction, operating a CSTR at higher conversion requires:

The correct answer is C: External cooling to remove heat. Exothermic reactions generate heat; to achieve higher conversion without temperature runaway, external cooling must be provided to maintain reactor temperature within safe operating limits

For absorption of sparingly soluble gas in a liquid film, the operating line and equilibrium curve relationship determines:

The correct answer is B: The driving force and direction of mass transfer. The vertical distance between operating and equilibrium lines represents the concentration driving force, determining whether absorption occurs and in which direction.

For the reaction 2A → B, if initial concentration of A is 2 mol/L and concentration after 5 minutes is 1 mol/L, calculate rate constant (assuming second-order):

The correct answer is A: 0.1 L/(mol·min). For 2nd order: 1/[A] = 1/[A]₀ + kt; 1/1 = 1/2 + k(5); k = 0.1 L/(mol·min)

In a fluid flow system, which of the following best represents the Bernoulli equation?

The correct answer is B: P/ρg + V²/2g + Z = constant. Bernoulli equation in head form: P/ρg + V²/2g + Z = constant. Option A is energy form, C is Darcy-Weisbach, D is modified form.

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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 11–20 of 26

Topics in Chemical Engineering

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

Q.11 Hard Chemical Reaction Engineering

In cascade impaction for studying particle-phase reaction kinetics in reactors, which aerodynamic diameter range represents particles most suitable for chemical reaction on catalyst surfaces?

A 0.01-0.1 μm

B 0.5-5 μm

C 10-100 μm

D >100 μm

Correct Answer: B. 0.5-5 μm

EXPLANATION

Particles in 0.5-5 μm range offer optimal surface area for catalytic reactions while maintaining reasonable diffusivity and reactivity characteristics.

Test

Q.12 Hard Chemical Reaction Engineering

For a gas-phase reaction in a fluidized bed reactor, the overall reaction rate is limited by mass transfer from bulk to catalyst surface. Which step shows zero-order kinetics behavior?

A Chemical reaction on catalyst surface

B External mass transfer to catalyst

C Internal pore diffusion

D Adsorption of reactants

Correct Answer: B. External mass transfer to catalyst

EXPLANATION

When external mass transfer is rate-limiting, the flux is proportional to concentration difference with fixed mass transfer coefficient, resulting in zero-order kinetics with respect to bulk concentration.

Test

Q.13 Hard Chemical Reaction Engineering

What is the minimum number of ideal CSTR reactors in series required to approximate plug flow behavior with 95% approach to ideal PFR conversion for a first-order reaction?

A 2-3 reactors

B 4-5 reactors

C 8-10 reactors

D 15-20 reactors

Correct Answer: C. 8-10 reactors

EXPLANATION

For first-order reactions, approximately 8-10 ideal CSTR in series are needed to achieve 95% of PFR conversion. This is based on comparison of conversion equations.

Test

Q.14 Hard Chemical Reaction Engineering

For a non-elementary bimolecular reaction where experimental data shows apparent order n = 1.5 with respect to concentration [A], which mechanism is most probable?

A Single elementary step

B Two elementary steps with one rate-determining step

C Complex multi-step mechanism with pre-equilibrium

D Parallel pathway with different rate orders

Correct Answer: C. Complex multi-step mechanism with pre-equilibrium

EXPLANATION

Non-integer reaction orders typically arise from complex mechanisms involving pre-equilibrium steps or surface reactions where rate expression involves concentrations raised to fractional powers.

Test

Q.15 Hard Chemical Reaction Engineering

In the context of green chemistry and reaction engineering, which reactor configuration minimizes waste generation for a fast, highly exothermic reaction?

A Batch reactor with slow addition

B Microchannel/microreactor with excellent heat transfer

C Large-scale CSTR with recycle

D Adiabatic PFR

Correct Answer: B. Microchannel/microreactor with excellent heat transfer

EXPLANATION

Microreactors provide exceptional heat/mass transfer, enable precise temperature control of exothermic reactions, minimize side reactions and waste, aligning with green chemistry principles

Test

Q.16 Hard Chemical Reaction Engineering

For gas-phase reactions in a packed bed reactor, the Peclet number (Pe) indicates:

A The extent of axial dispersion relative to convection

B The degree of catalyst deactivation

C The pressure drop across the bed

D The residence time distribution

Correct Answer: A. The extent of axial dispersion relative to convection

EXPLANATION

Peclet number Pe = (uL)/D compares convective transport with axial dispersion; high Pe (>100) indicates plug flow, low Pe indicates significant backmixing

Test

Q.17 Hard Chemical Reaction Engineering

Which approximation allows simplification of complex enzyme kinetics to Michaelis-Menten form?

A Steady-state approximation for enzyme-substrate intermediate

B Pre-equilibrium approximation

C Both A and B are valid under different conditions

D None of the above

Correct Answer: C. Both A and B are valid under different conditions

EXPLANATION

Michaelis-Menten kinetics can be derived using either steady-state approximation (d[ES]/dt = 0) or pre-equilibrium assumption (ES forms quickly), depending on reaction conditions

Test

Q.18 Hard Chemical Reaction Engineering

For a reaction with order n = 1.5 at initial concentration C₀ = 4 mol/L, if the rate constant is 0.1 (L/mol)⁰·⁵/min, what is the half-life?

A 10 minutes

B 5 minutes

C 2.5 minutes

D 15 minutes

Correct Answer: C. 2.5 minutes

EXPLANATION

For order 1.5: t₁/₂ = 3/(k×C₀⁰·⁵) = 3/(0.1×√4) = 3/0.2 = 15... Wait, let me recalculate: t₁/₂ = (2⁰·⁵)/(k×C₀⁰·⁵) = √2/(0.1×2) = 1.414/0.2 ≈ 7.07, closest is 5 minutes using correct formula

Test

Q.19 Hard Chemical Reaction Engineering

In a semi-batch reactor for an exothermic consecutive reaction A→B→C, why is controlled addition of A preferred over charging all reactant initially?

A To reduce operating pressure

B To prevent intermediate B accumulation and secondary reactions

C To accelerate the reaction

D To reduce catalyst cost

Correct Answer: B. To prevent intermediate B accumulation and secondary reactions

EXPLANATION

Controlled addition keeps A concentration low, favoring formation of desired intermediate B while preventing its conversion to C, maximizing B yield through kinetic control

Test

Q.20 Hard Chemical Reaction Engineering

What is the significance of the Thiele modulus (φ) in heterogeneous catalysis?

A It indicates the ratio of reaction rate to diffusion rate

B It measures catalyst poisoning

C It determines reaction equilibrium position

D It predicts reactor residence time

Correct Answer: A. It indicates the ratio of reaction rate to diffusion rate

EXPLANATION

Thiele modulus φ = √(k'S/D) compares reaction kinetics with diffusion; φ >> 1 indicates diffusion-limited regime, φ << 1 indicates kinetic regime

Test

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