ARKANSAS CHEMICAL ENGINEERING
PROFESSIONAL EXAM QUESTIONS WITH
CORRECT ANSWERS AND RATIONALES LATEST
2026-2027 TREND
Questions 1–10: Fundamentals and Material Balances
1. A steady-state process receives 100 kg/h of a feed containing 40 wt%
component A. If the product stream contains 80 wt% A and there are no losses,
what is the product flow rate?
A. 20 kg/h
B. 40 kg/h
C. 50 kg/h
D. 80 kg/h
Correct Answer: C. 50 kg/h
Rationale: The feed contains 40 kg/h of A. Therefore, product flow = 40/0.80 = 50
kg/h.
2. Which principle is the basis of a material balance around a nonreactive steady-
state process?
A. Energy cannot be destroyed
B. Mass entering equals mass leaving
C. Pressure equals temperature
D. Entropy is always constant
Correct Answer: B. Mass entering equals mass leaving
Rationale: For a steady-state nonreactive system with no accumulation, the total
mass entering must equal the total mass leaving.
,3. In a chemical reaction, the limiting reactant is the reactant that:
A. Has the highest molecular weight
B. Is present in the largest quantity
C. Is consumed first according to stoichiometry
D. Has the lowest concentration
Correct Answer: C. Is consumed first according to stoichiometry
Rationale: The limiting reactant determines the theoretical maximum amount of
product that can be formed.
4. A process has a 90% conversion of reactant A. If 1,000 mol/h of A enters the
reactor, how much A remains unreacted?
A. 10 mol/h
B. 50 mol/h
C. 100 mol/h
D. 900 mol/h
Correct Answer: C. 100 mol/h
Rationale: Unreacted A = 1,000 × (1 − 0.90) = 100 mol/h.
5. What is the purpose of a recycle stream in a chemical process?
A. To eliminate all energy consumption
B. To recover unreacted or valuable material
C. To increase waste generation
D. To prevent heat transfer
Correct Answer: B. To recover unreacted or valuable material
Rationale: Recycling can improve raw-material utilization, increase overall
conversion, and reduce waste.
, 6. A process stream contains 25 kg of solute and 75 kg of solvent. The solute mass
fraction is:
A. 0.20
B. 0.25
C. 0.33
D. 0.75
Correct Answer: B. 0.25
Rationale: Mass fraction = 25/(25 + 75) = 0.25.
7. Which balance must be applied when a component participates in a chemical
reaction?
A. Total mass balance only
B. Component balance including generation and consumption
C. Momentum balance only
D. Mechanical energy balance only
Correct Answer: B. Component balance including generation and
consumption
Rationale: Reaction terms must be included because chemical reactions generate
and consume species.
8. The degree of freedom of a process system is zero when:
A. There are no variables
B. There are more unknowns than equations
C. The number of independent equations equals the number of unknowns
D. The system has no material streams
Correct Answer: C. The number of independent equations equals the number
of unknowns
PROFESSIONAL EXAM QUESTIONS WITH
CORRECT ANSWERS AND RATIONALES LATEST
2026-2027 TREND
Questions 1–10: Fundamentals and Material Balances
1. A steady-state process receives 100 kg/h of a feed containing 40 wt%
component A. If the product stream contains 80 wt% A and there are no losses,
what is the product flow rate?
A. 20 kg/h
B. 40 kg/h
C. 50 kg/h
D. 80 kg/h
Correct Answer: C. 50 kg/h
Rationale: The feed contains 40 kg/h of A. Therefore, product flow = 40/0.80 = 50
kg/h.
2. Which principle is the basis of a material balance around a nonreactive steady-
state process?
A. Energy cannot be destroyed
B. Mass entering equals mass leaving
C. Pressure equals temperature
D. Entropy is always constant
Correct Answer: B. Mass entering equals mass leaving
Rationale: For a steady-state nonreactive system with no accumulation, the total
mass entering must equal the total mass leaving.
,3. In a chemical reaction, the limiting reactant is the reactant that:
A. Has the highest molecular weight
B. Is present in the largest quantity
C. Is consumed first according to stoichiometry
D. Has the lowest concentration
Correct Answer: C. Is consumed first according to stoichiometry
Rationale: The limiting reactant determines the theoretical maximum amount of
product that can be formed.
4. A process has a 90% conversion of reactant A. If 1,000 mol/h of A enters the
reactor, how much A remains unreacted?
A. 10 mol/h
B. 50 mol/h
C. 100 mol/h
D. 900 mol/h
Correct Answer: C. 100 mol/h
Rationale: Unreacted A = 1,000 × (1 − 0.90) = 100 mol/h.
5. What is the purpose of a recycle stream in a chemical process?
A. To eliminate all energy consumption
B. To recover unreacted or valuable material
C. To increase waste generation
D. To prevent heat transfer
Correct Answer: B. To recover unreacted or valuable material
Rationale: Recycling can improve raw-material utilization, increase overall
conversion, and reduce waste.
, 6. A process stream contains 25 kg of solute and 75 kg of solvent. The solute mass
fraction is:
A. 0.20
B. 0.25
C. 0.33
D. 0.75
Correct Answer: B. 0.25
Rationale: Mass fraction = 25/(25 + 75) = 0.25.
7. Which balance must be applied when a component participates in a chemical
reaction?
A. Total mass balance only
B. Component balance including generation and consumption
C. Momentum balance only
D. Mechanical energy balance only
Correct Answer: B. Component balance including generation and
consumption
Rationale: Reaction terms must be included because chemical reactions generate
and consume species.
8. The degree of freedom of a process system is zero when:
A. There are no variables
B. There are more unknowns than equations
C. The number of independent equations equals the number of unknowns
D. The system has no material streams
Correct Answer: C. The number of independent equations equals the number
of unknowns
