In transient heat conduction, the Fourier number (Fo = α·t/L²) represents:

The correct answer is D: Measure of penetration depth of thermal disturbance. Fourier number represents the dimensionless time or the measure of how far thermal disturbances have penetrated into the material. High Fo indicates significant internal temperature changes, while low Fo indicates the disturbance is confined to the surface.

For a Newtonian fluid, shear stress (τ) is related to shear rate (dV/dy) by:

The correct answer is A: τ = μ(dV/dy). Newton's law of viscosity: τ = μ(dV/dy). Option B is power law (non-Newtonian), C is Bingham plastic model.

In the context of reaction kinetics, which statement best describes the rate-determining step (RDS) in a multi-step reaction mechanism?

The correct answer is B: It is the slowest step that controls the overall reaction rate. The rate-determining step is the slowest elementary step in the reaction mechanism, which governs the overall rate of the reaction regardless of its position in the sequence

A steel rod (k = 50 W/m·K) of diameter 10 mm and length 100 mm is exposed to air at 25°C with h = 20 W/m²·K. The rod is maintained at 100°C at one end. Calculate the fin efficiency if m = √(hP/kA) = 8.37 m⁻¹.

The correct answer is B: 0.72. mL = 8.37 × 0.1 = 0.837. Fin efficiency η = tanh(mL)/(mL) = tanh(0.837)/0.837 = 0.688/0.837 ≈ 0.72

In a binary gas mixture, if component A is highly soluble in the liquid phase compared to component B, which statement is true regarding absorption?

The correct answer is C: Component A controls the overall mass transfer rate. High solubility of A means low liquid-phase resistance for A, making the gas-phase resistance dominant. Thus, gas-phase mass transfer resistance controls the overall rate for A.

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Chemical Engineering
Chemical Reaction Engineering

Process design, thermodynamics, reactions

23 Q 5 Topics Take Mock Test

Difficulty: All Easy Medium Hard 1–10 of 23

Topics in Chemical Engineering

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

Q.1 Easy Chemical Reaction Engineering

In CSTR, if inlet concentration C_A0 = 2 M, outlet concentration C_A = 0.5 M, what is fractional conversion?

A 0.25

B 0.5

C 0.75

D 1.0

Correct Answer: C. 0.75

EXPLANATION

Conversion X = (C_A0 - C_A)/C_A0 = (2 - 0.5)/2 = 0.75 or 75%.

Test

Q.2 Easy Chemical Reaction Engineering

What is the space-time (τ) in a PFR if reactor volume is 100 L and volumetric feed rate is 10 L/min?

A 0.1 min

B 1 min

C 10 min

D 100 min

Correct Answer: C. 10 min

EXPLANATION

Space-time τ = V/v₀ = 100/10 = 10 min.

Test

Q.3 Easy Chemical Reaction Engineering

Which of the following statements about adiabatic reactors is correct?

A Temperature remains constant throughout

B Heat exchange with surroundings occurs freely

C Temperature changes according to heat of reaction

D No chemical reaction occurs

Correct Answer: C. Temperature changes according to heat of reaction

EXPLANATION

In adiabatic reactors, Q = 0, so ΔT depends on heat of reaction (ΔH_r) and heat capacity of reactants.

Test

Q.4 Easy Chemical Reaction Engineering

For a reversible reaction at equilibrium, which statement is true?

A Forward reaction rate = zero

B Forward reaction rate = Reverse reaction rate

C Reverse reaction rate = zero

D Both rates are maximum

Correct Answer: B. Forward reaction rate = Reverse reaction rate

EXPLANATION

At equilibrium, the net rate is zero because forward and reverse reaction rates are equal.

Test

Q.5 Easy Chemical Reaction Engineering

For the reaction A + B → C, the rate law is r = kC_A²C_B. What is the overall order of reaction?

A First order

B Second order

C Third order

D Cannot be determined

Correct Answer: C. Third order

EXPLANATION

Overall order = sum of individual orders = 2 + 1 = 3.

Test

Q.6 Easy Chemical Reaction Engineering

What is the order of reaction if the half-life period is independent of initial concentration?

A Zero order

B First order

C Second order

D Third order

Correct Answer: B. First order

EXPLANATION

For first-order reactions, t₁/₂ = 0.693/k, which is independent of initial concentration C₀.

Test

Q.7 Easy Chemical Reaction Engineering

For the reaction 2A + B → Products, if the reaction is 2nd order in A and 1st order in B, the rate equation is:

A r = k[A]²[B]

B r = k[A][B]²

C r = k([A]² + [B])

D r = k[A]³[B]

Correct Answer: A. r = k[A]²[B]

EXPLANATION

Reaction order is determined by experimental data, not stoichiometry. The given orders are 2nd in A and 1st in B, so rate law is r = k[A]²[B].

Test

Q.8 Easy Chemical Reaction Engineering

The conversion in a batch reactor at any time can be found by integrating the rate equation. For a first-order reaction, the half-life is:

A Independent of initial concentration

B Proportional to initial concentration

C Inversely proportional to the rate constant

D Both A and C are correct

Correct Answer: D. Both A and C are correct

EXPLANATION

For first-order: t₁/₂ = ln(2)/k = 0.693/k, which is independent of C₀ and inversely proportional to k.

Test

Q.9 Easy Chemical Reaction Engineering

The Damköhler number (Da) for a chemical reaction is defined as the ratio of:

A Reaction time to residence time

B Residence time to reaction time

C Conversion to equilibrium conversion

D Rate constant to flow velocity

Correct Answer: B. Residence time to reaction time

EXPLANATION

Da = (residence time)/(characteristic reaction time) = kτC^(n-1). When Da >> 1, reaction is fast; Da << 1, reaction is slow.

Test

Q.10 Easy Chemical Reaction Engineering

Which of the following statements about residence time distribution (RTD) is correct?

A RTD is independent of reactor geometry and flow conditions

B RTD describes the fraction of fluid elements spending time between t and t+dt in the reactor

C RTD is only applicable to laminar flow reactors

D RTD cannot be experimentally determined using tracer studies

Correct Answer: B. RTD describes the fraction of fluid elements spending time between t and t+dt in the reactor

EXPLANATION

RTD characterizes how long different fluid elements spend in a reactor and is fundamental to reactor design, independent of whether flow is laminar or turbulent.

Test

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