Principles and Practice of Engineering (PE) Chemical
Examination Questions And Correct Answers (Verified
Answers) Plus Rationales 2025/2026 Q&A | Instant
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1. The rate of a first-order reaction is 0.5 s⁻¹. If the initial concentration is 1
M, what is the concentration after 2 seconds?
A) 0.37 M
B) 0.37 M
C) 0.61 M
D) 0.25 M
Rationale: First-order decay follows [A] = [A₀]e^(-kt). [A] = 1 * e^(-0.52) ≈ 0.37
M.*
2. Which of the following is a characteristic of an ideal solution?
A) Non-volatile components
B) ΔH_mix = 0
C) Positive deviation from Raoult’s law
D) Immiscibility
Rationale: Ideal solutions have no enthalpy change upon mixing (ΔH_mix = 0)
and obey Raoult’s law exactly.
3. For a perfectly stirred tank reactor (PSTR) with a first-order reaction, the
steady-state exit concentration is given by:
A) C = C₀ e^(-kτ)
B) C = C₀ / (1 + kτ)
C) C = C₀(1 - kτ)
D) C = C₀ ln(1 + kτ)
Rationale: For a PSTR, C_out = C_in / (1 + kτ), where τ is the residence time.
4. Which property is intensive?
,A) Mass
B) Volume
C) Density
D) Total energy
Rationale: Intensive properties do not depend on the size of the system; density
is independent of system mass.
5. The dimensionless group representing inertial vs viscous forces in fluid
flow is:
A) Reynolds number
B) Reynolds number
C) Prandtl number
D) Nusselt number
Rationale: Re = ρVD/μ compares inertial to viscous forces.
6. Which is the main assumption in using the ideal gas law?
A) Molecules exert intermolecular forces
B) Molecules occupy finite volume
C) Molecules do not interact
D) Gas is always at high pressure
Rationale: Ideal gas law assumes negligible intermolecular forces and
molecular volume.
7. In distillation, the component with the lower boiling point:
A) Remains in the bottom
B) Enriches in the vapor phase
C) Forms azeotrope with high BP component
D) Is unseparated
Rationale: Lower boiling point components vaporize preferentially in
distillation.
8. Which of the following is a batch process?
, A) Continuous stirred tank reactor (CSTR)
B) Fermentation in a lab-scale bioreactor
C) Pipeline oil transport
D) Continuous distillation
Rationale: Batch processes have a fixed quantity processed with no continuous
inflow/outflow.
9. The van’t Hoff factor for Na₂SO₄ in water is approximately:
A) 1
B) 2
C) 3
D) 4
Rationale: Na₂SO₄ dissociates into 3 ions (2 Na⁺ + 1 SO₄²⁻).
10. Which is true for a zero-order reaction?
A) Rate depends on concentration
B) Rate increases with [A]
C) Rate is constant
D) Half-life is independent of rate constant
Rationale: Zero-order reactions have constant rate independent of reactant
concentration.
11. In heat exchanger design, the Log Mean Temperature Difference (LMTD)
is used to:
A) Measure pressure drop
B) Estimate heat transfer rate
C) Calculate flow velocity
D) Determine material corrosion
Rationale: Q = U A LMTD gives heat transferred in steady-state conditions.
12. The activation energy of a reaction is 50 kJ/mol. At constant temperature,
increasing the temperature will:
Examination Questions And Correct Answers (Verified
Answers) Plus Rationales 2025/2026 Q&A | Instant
Download Pdf
1. The rate of a first-order reaction is 0.5 s⁻¹. If the initial concentration is 1
M, what is the concentration after 2 seconds?
A) 0.37 M
B) 0.37 M
C) 0.61 M
D) 0.25 M
Rationale: First-order decay follows [A] = [A₀]e^(-kt). [A] = 1 * e^(-0.52) ≈ 0.37
M.*
2. Which of the following is a characteristic of an ideal solution?
A) Non-volatile components
B) ΔH_mix = 0
C) Positive deviation from Raoult’s law
D) Immiscibility
Rationale: Ideal solutions have no enthalpy change upon mixing (ΔH_mix = 0)
and obey Raoult’s law exactly.
3. For a perfectly stirred tank reactor (PSTR) with a first-order reaction, the
steady-state exit concentration is given by:
A) C = C₀ e^(-kτ)
B) C = C₀ / (1 + kτ)
C) C = C₀(1 - kτ)
D) C = C₀ ln(1 + kτ)
Rationale: For a PSTR, C_out = C_in / (1 + kτ), where τ is the residence time.
4. Which property is intensive?
,A) Mass
B) Volume
C) Density
D) Total energy
Rationale: Intensive properties do not depend on the size of the system; density
is independent of system mass.
5. The dimensionless group representing inertial vs viscous forces in fluid
flow is:
A) Reynolds number
B) Reynolds number
C) Prandtl number
D) Nusselt number
Rationale: Re = ρVD/μ compares inertial to viscous forces.
6. Which is the main assumption in using the ideal gas law?
A) Molecules exert intermolecular forces
B) Molecules occupy finite volume
C) Molecules do not interact
D) Gas is always at high pressure
Rationale: Ideal gas law assumes negligible intermolecular forces and
molecular volume.
7. In distillation, the component with the lower boiling point:
A) Remains in the bottom
B) Enriches in the vapor phase
C) Forms azeotrope with high BP component
D) Is unseparated
Rationale: Lower boiling point components vaporize preferentially in
distillation.
8. Which of the following is a batch process?
, A) Continuous stirred tank reactor (CSTR)
B) Fermentation in a lab-scale bioreactor
C) Pipeline oil transport
D) Continuous distillation
Rationale: Batch processes have a fixed quantity processed with no continuous
inflow/outflow.
9. The van’t Hoff factor for Na₂SO₄ in water is approximately:
A) 1
B) 2
C) 3
D) 4
Rationale: Na₂SO₄ dissociates into 3 ions (2 Na⁺ + 1 SO₄²⁻).
10. Which is true for a zero-order reaction?
A) Rate depends on concentration
B) Rate increases with [A]
C) Rate is constant
D) Half-life is independent of rate constant
Rationale: Zero-order reactions have constant rate independent of reactant
concentration.
11. In heat exchanger design, the Log Mean Temperature Difference (LMTD)
is used to:
A) Measure pressure drop
B) Estimate heat transfer rate
C) Calculate flow velocity
D) Determine material corrosion
Rationale: Q = U A LMTD gives heat transferred in steady-state conditions.
12. The activation energy of a reaction is 50 kJ/mol. At constant temperature,
increasing the temperature will:
