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

For an isothermal reversible expansion of 2 moles of ideal gas from 10 L to 50 L at 300 K:

The correct answer is C: W = -nRT ln(V_f/V_i) ≈ -12.88 kJ. W = -∫PdV = -nRT ln(V_f/V_i) = -2×8.314×300×ln(5) ≈ -12.88 kJ. Work done by system is negative (work done on surroundings).

The virial equation of state truncated after second term is: PV = nRT(1 + B(T)P/RT). What does B(T) represent?

The correct answer is D: All of the above. B(T) is the second virial coefficient that accounts for molecular interactions. It corrects ideal gas behavior and is temperature-dependent, directly representing non-ideality.

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?

The correct answer is C: Complex multi-step mechanism with pre-equilibrium. 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.

For the decomposition of N₂O₅ following first-order kinetics with k = 0.0074 s⁻¹, what fraction of reactant remains after 300 seconds?

The correct answer is A: 0.18. [A]/[A]₀ = e^(-kt) = e^(-0.0074×300) = e^(-2.22) ≈ 0.18 or 18% remains

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Chemical Engineering
Chemical Reaction Engineering

Process design, thermodynamics, reactions

51 Q 5 Topics Take Mock Test

Difficulty: All Easy Medium Hard 41–50 of 51

Topics in Chemical Engineering

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

Q.41 Medium Chemical Reaction Engineering

In a CSTR operating at steady state, the space time (τ) for a first-order reaction is 5 minutes. What is the conversion if k = 0.2 min⁻¹?

A 0.5 or 50%

B 0.667 or 66.7%

C 0.333 or 33.3%

D 0.75 or 75%

Correct Answer: B. 0.667 or 66.7%

EXPLANATION

For CSTR: τ = (CA0 - CA)/(kCA) = X/(k(1-X)). Solving: 5 = X/(0.2(1-X)) gives X = 0.667 or 66.7%

Test

Q.42 Medium Chemical Reaction Engineering

For a second-order reaction A+B→C with equal initial concentrations of 1 mol/L, if the rate constant is 0.5 L/(mol·min), what is the time required for 50% conversion?

A 2 minutes

B 1 minute

C 4 minutes

D 0.5 minutes

Correct Answer: A. 2 minutes

EXPLANATION

For second-order reaction with CA0 = CB0: 1/CA - 1/CA0 = kt. At 50% conversion, CA = 0.5. So (1/0.5 - 1/1) = 0.5×t gives t = 2 minutes

Test

Q.43 Medium Chemical Reaction Engineering

For autocatalytic reactions, which reactor gives highest conversion at equilibrium?

A Batch reactor

B CSTR

C PFR

D All reactors give same equilibrium conversion

Correct Answer: D. All reactors give same equilibrium conversion

EXPLANATION

Equilibrium conversion is thermodynamically determined and independent of reactor type

Test

Q.44 Medium Chemical Reaction Engineering

For an exothermic reaction in an adiabatic reactor, what happens to the reaction rate as conversion increases?

A Decreases due to equilibrium limitations

B Remains constant

C Increases due to temperature rise

D Becomes independent of temperature

Correct Answer: C. Increases due to temperature rise

EXPLANATION

Adiabatic reactor: no heat removal; exothermic reaction raises temperature, increasing k and hence rate

Test

Q.45 Medium Chemical Reaction Engineering

In enzyme catalysis, what does the Michaelis-Menten constant (K_m) represent?

A Substrate concentration at half maximum velocity

B Dissociation constant of enzyme-product complex

C Maximum velocity of enzyme

D Activation energy of enzyme-catalyzed reaction

Correct Answer: A. Substrate concentration at half maximum velocity

EXPLANATION

K_m represents substrate concentration [S] at which reaction velocity = V_max/2

Test

Q.46 Medium Chemical Reaction Engineering

The Damköhler number (Da) in chemical reactor design represents:

A Ratio of reaction rate to diffusion rate

B Ratio of residence time to reaction time

C Ratio of reactant concentration to product concentration

D Ratio of temperature to activation energy

Correct Answer: B. Ratio of residence time to reaction time

EXPLANATION

Da = kτ = (reaction rate constant × residence time), dimensionless number indicating reaction extent

Test

Q.47 Medium Chemical Reaction Engineering

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):

A 0.1 L/(mol·min)

B 0.2 L/(mol·min)

C 0.05 L/(mol·min)

D 0.01 L/(mol·min)

Correct Answer: A. 0.1 L/(mol·min)

EXPLANATION

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

Test

Q.48 Medium Chemical Reaction Engineering

In a catalytic reaction, which parameter does NOT affect the rate of reaction?

A Catalyst concentration

B Temperature

C Gibbs free energy of reaction

D Reactant concentration

Correct Answer: C. Gibbs free energy of reaction

EXPLANATION

Catalyst doesn't change ΔG or equilibrium position; it only lowers Eₐ. ΔG determines feasibility, not rate

Test

Q.49 Medium Chemical Reaction Engineering

For parallel reactions A→B and A→C, the selectivity of B over C is defined as:

A Rate of B formation/Rate of C formation

B Conversion of A to B

C [B]/[C] at equilibrium

D Yield of B/Total conversion

Correct Answer: A. Rate of B formation/Rate of C formation

EXPLANATION

Selectivity = rate of desired product formation/rate of undesired product formation

Test

Q.50 Medium Chemical Reaction Engineering

In a CSTR operating at steady state, if residence time is doubled and inlet concentration remains constant, how does conversion change for a first-order reaction?

A Conversion decreases

B Conversion increases

C Conversion remains same

D Conversion becomes zero

Correct Answer: B. Conversion increases

EXPLANATION

For CSTR: X = kτ/(1+kτ). Increasing τ increases conversion for first-order reactions

Test

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