Chemical Engineering
Examination — 2027 Practice
Exam Questions | Answers + Rationales
Section I — Material & Energy Balances
1. A process feed contains 40 wt% A and flows at 250 kg/h. What is the mass flow of A?
A. 50 kg/h
B. 75 kg/h
C. 100 kg/h
D. 150 kg/h
Answer: C. 100 kg/h
Rationale: 250(0.40)=100250(0.40)=100 kg/h of A.
2. At steady state, with no accumulation and no chemical reaction, the overall mass balance is:
A. Input = accumulation
B. Input = output
C. Output = generation
D. Input + output = 0
Answer: B. Input = output
Rationale: The general balance is input − output + generation − consumption = accumulation.
With no reaction and zero accumulation, input equals output.
3. A stream contains 20 mol A and 80 mol B. The mole fraction of A is:
A. 0.02
B. 0.20
C. 0.25
D. 0.80
Answer: B. 0.20
Rationale: xA=20/(20+80)=0.20x_A=20/(20+80)=0.20.
,4. A 100-kg feed contains 30 kg water and 70 kg ethanol. The mass fraction of water is:
A. 0.03
B. 0.30
C. 0.70
D. 3.33
Answer: B. 0.30
Rationale: Mass fraction = component mass/total mass = 30/100 = 0.30.
5. Which quantity is conserved in an ordinary overall material balance?
A. Temperature
B. Pressure
C. Mass
D. Entropy
Answer: C. Mass
Rationale: Mass conservation is fundamental to chemical-process balances.
6. A process receives 500 kg/h and produces 350 kg/h in one outlet. If there is no accumulation,
the remaining outlet flow must be:
A. 100 kg/h
B. 150 kg/h
C. 250 kg/h
D. 850 kg/h
Answer: B. 150 kg/h
Rationale: Total output must equal 500 kg/h, so 500−350=150500-350=150 kg/h.
7. For a steady-state system with a chemical reaction, which balance is generally required for
determining individual species flows?
A. Component balance
B. Color balance
C. Geometry balance
D. Surface-area balance
, Answer: A. Component balance
Rationale: Species/component balances account for inlet, outlet, generation, and consumption.
8. A 200-mol feed contains 25 mol% A. How many moles of A enter?
A. 25 mol
B. 40 mol
C. 50 mol
D. 75 mol
Answer: C. 50 mol
Rationale: 200(0.25)=50200(0.25)=50 mol.
9. An energy balance is fundamentally based on conservation of:
A. Mass
B. Energy
C. Volume
D. Concentration
Answer: B. Energy
Rationale: Energy cannot be created or destroyed; it can only be transferred or transformed.
10. Sensible heating of a substance with constant heat capacity is calculated using:
A. Q=mCpΔTQ=mC_p\Delta T
B. Q=m/(CpΔT)Q=m/\left(C_p\Delta T\right)
C. Q=Cp/(mΔT)Q=C_p/(m\Delta T)
D. Q=mCp/TQ=mC_p/T
Answer: A. Q=mCpΔTQ=mC_p\Delta T
Rationale: This is the standard constant-CpC_p sensible-heat relationship.
Section II — Thermodynamics
11. Which is a state function?
Examination — 2027 Practice
Exam Questions | Answers + Rationales
Section I — Material & Energy Balances
1. A process feed contains 40 wt% A and flows at 250 kg/h. What is the mass flow of A?
A. 50 kg/h
B. 75 kg/h
C. 100 kg/h
D. 150 kg/h
Answer: C. 100 kg/h
Rationale: 250(0.40)=100250(0.40)=100 kg/h of A.
2. At steady state, with no accumulation and no chemical reaction, the overall mass balance is:
A. Input = accumulation
B. Input = output
C. Output = generation
D. Input + output = 0
Answer: B. Input = output
Rationale: The general balance is input − output + generation − consumption = accumulation.
With no reaction and zero accumulation, input equals output.
3. A stream contains 20 mol A and 80 mol B. The mole fraction of A is:
A. 0.02
B. 0.20
C. 0.25
D. 0.80
Answer: B. 0.20
Rationale: xA=20/(20+80)=0.20x_A=20/(20+80)=0.20.
,4. A 100-kg feed contains 30 kg water and 70 kg ethanol. The mass fraction of water is:
A. 0.03
B. 0.30
C. 0.70
D. 3.33
Answer: B. 0.30
Rationale: Mass fraction = component mass/total mass = 30/100 = 0.30.
5. Which quantity is conserved in an ordinary overall material balance?
A. Temperature
B. Pressure
C. Mass
D. Entropy
Answer: C. Mass
Rationale: Mass conservation is fundamental to chemical-process balances.
6. A process receives 500 kg/h and produces 350 kg/h in one outlet. If there is no accumulation,
the remaining outlet flow must be:
A. 100 kg/h
B. 150 kg/h
C. 250 kg/h
D. 850 kg/h
Answer: B. 150 kg/h
Rationale: Total output must equal 500 kg/h, so 500−350=150500-350=150 kg/h.
7. For a steady-state system with a chemical reaction, which balance is generally required for
determining individual species flows?
A. Component balance
B. Color balance
C. Geometry balance
D. Surface-area balance
, Answer: A. Component balance
Rationale: Species/component balances account for inlet, outlet, generation, and consumption.
8. A 200-mol feed contains 25 mol% A. How many moles of A enter?
A. 25 mol
B. 40 mol
C. 50 mol
D. 75 mol
Answer: C. 50 mol
Rationale: 200(0.25)=50200(0.25)=50 mol.
9. An energy balance is fundamentally based on conservation of:
A. Mass
B. Energy
C. Volume
D. Concentration
Answer: B. Energy
Rationale: Energy cannot be created or destroyed; it can only be transferred or transformed.
10. Sensible heating of a substance with constant heat capacity is calculated using:
A. Q=mCpΔTQ=mC_p\Delta T
B. Q=m/(CpΔT)Q=m/\left(C_p\Delta T\right)
C. Q=Cp/(mΔT)Q=C_p/(m\Delta T)
D. Q=mCp/TQ=mC_p/T
Answer: A. Q=mCpΔTQ=mC_p\Delta T
Rationale: This is the standard constant-CpC_p sensible-heat relationship.
Section II — Thermodynamics
11. Which is a state function?
