The compressibility factor Z for a real gas at high pressures typically:

The correct answer is D: Can be either above or below 1 depending on temperature. At low T, attractive forces dominate (Z 1). The Boyle temperature is where Z ≈ 1. Pressure and temperature both influence Z significantly.

For an ideal gas undergoing adiabatic compression, the entropy change is:

The correct answer is C: Zero. For a reversible adiabatic process, dq = 0, therefore ΔS = ∫dq_rev/T = 0. Entropy remains constant during reversible adiabatic processes.

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

The correct answer is A: It indicates the ratio of reaction rate to diffusion rate. Thiele modulus φ = √(k'S/D) compares reaction kinetics with diffusion; φ >> 1 indicates diffusion-limited regime, φ

For a polytropic process PV^n = constant, if n = γ (heat capacity ratio), the process is:

The correct answer is B: Adiabatic. For adiabatic process of ideal gas, PV^γ = constant where γ = Cp/Cv. This is the defining equation for adiabatic polytropic process.

The thermal diffusivity (α) has dimensions of which of the following?

The correct answer is A: Length²/Time. Thermal diffusivity α = k/(ρ·C_p) has dimensions L²/t, representing how fast thermal disturbances propagate through a material.

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Chemical Engineering

Process design, thermodynamics, reactions

247 Q 5 Topics Take Mock Test

Difficulty: All Easy Medium Hard 91–100 of 247

Topics in Chemical Engineering

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

Q.91 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.92 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.93 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.94 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.95 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.96 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.97 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.98 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.99 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

Q.100 Medium Chemical Reaction Engineering

Which type of reactor provides the best conversion for a reversible exothermic reaction?

A Batch reactor with cooling

B CSTR at high temperature

C Plug flow reactor with heat removal

D Fixed bed reactor without temperature control

Correct Answer: C. Plug flow reactor with heat removal

EXPLANATION

PFR with heat removal maintains optimal temperature profile and continuous removal of products, favoring forward reaction equilibrium

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