FLORIDA BOARD OF PROFESSIONAL
ENGINEERS PRINCIPLES AND PRACTICE
CHEMICAL EXAM WITH ACTUAL
QUESTIONS AND VERIFIED ANSWERS,
PLUS EXPLAINED RATIONALES/EXPERT
VERIFIED FOR GUARANTEED 100% PASS
2026/LATEST UPDATE/INSTANT
DOWNLOAD PDF
1. Material Balance — Recycle
A continuous process receives 1,000 kg/h of a feed containing 30 wt% A
and 70 wt% inert material. A separator recovers 90% of A in the product
stream. The remaining stream is recycled completely to the reactor. If
the reactor has no reaction and no accumulation, what is the approximate
fresh-feed requirement of A needed to obtain 270 kg/h of A in the
product?
A. 270 kg/h
B. 300 kg/h
C. 330 kg/h
D. 360 kg/h
Answer: B. 300 kg/h
Rationale: The separator recovers 90% of the A entering the separator.
To obtain 270 kg/h of A in the product, the total A entering the
separator must be 270/0.90 = 300 kg/h. At steady state, the recycle does
not alter the overall balance around the entire process because
internal recycle streams cancel. Therefore, the required fresh A input
is 300 kg/h.
1
,2. Stoichiometry — Limiting Reactant
A reactor performs the reaction:
2A+B→2C
A feed contains 100 mol/h of A and 80 mol/h of B. Assuming complete
conversion of the limiting reactant, what is the maximum production rate
of C?
A. 80 mol/h
B. 100 mol/h
C. 160 mol/h
D. 180 mol/h
Answer: B. 100 mol/h
Rationale: The stoichiometric requirement is 2 mol A for every 1 mol
B. For 80 mol/h of B, 160 mol/h of A would be required, but only 100
mol/h are available. Thus A is limiting. Because 2 mol A produce 2
mol C, the molar production of C equals the molar consumption of A,
giving 100 mol/h C.
3. Combustion — Excess Air
Methane is completely combusted according to:
CH4+2O2→CO2+2H2O
Air contains 21 mol% oxygen. If 25% excess air is supplied per mole of
methane, what is the approximate molar flow of air required per mole of
methane?
A. 9.52 mol
B. 10.00 mol
2
,C. 11.90 mol
D. 12.50 mol
Answer: C. 11.90 mol
Rationale: The theoretical oxygen requirement is 2 mol O₂/mol CH₄.
With 25% excess air, the actual oxygen supplied is 2(1.25) = 2.5 mol
O₂. Since air contains 0.21 mol O₂ per mole of air, the required air is
2.5/0.21 ≈ 11.90 mol air per mole CH₄.
4. Energy Balance — Sensible Heating
A process heats 5,000 kg/h of a liquid from 25°C to 85°C. The average
heat capacity is 4.0 kJ/(kg·K). Neglecting heat losses, what heat-transfer
rate is required?
A. 0.33 MW
B. 0.67 MW
C. 1.20 MW
D. 1.50 MW
Answer: B. 0.33 MW
Rationale: The heat duty is Q=m˙CpΔT. Therefore,
Q=(5,000)(4.0)(85−25)=1,200,000 kJ/h. Dividing by 3,600 s/h gives
approximately 333 kW, or 0.33 MW.
5. Thermodynamics — Ideal Gas
An ideal gas occupies 2.0 m³ at 300 K and 500 kPa absolute pressure.
What is the approximate number of kilomoles present?
Use R=8.314 kPa·m³/(kmol·K).
A. 0.20 kmol
B. 0.40 kmol
3
, C. 0.60 kmol
D. 1.20 kmol
Answer: B. 0.40 kmol
Rationale: From PV=nRT, n=PV/(RT). Substituting gives
n=(500)(2)/(8.314)(300)≈0.401 kmol. Therefore, approximately 0.40
kmol of gas is present.
6. Thermodynamics — First Law
A steady-flow compressor receives gas with negligible changes in
kinetic and potential energy. The gas enters with enthalpy of 300 kJ/kg
and exits at 500 kJ/kg. If heat loss from the compressor is 20 kJ/kg, what
shaft work input is required?
A. 180 kJ/kg
B. 200 kJ/kg
C. 220 kJ/kg
D. 520 kJ/kg
Answer: C. 220 kJ/kg
Rationale: For a compressor, the required work input is approximately
Win=Δh+Qout when kinetic and potential effects are negligible. Thus
Win=(500−300)+20=220 kJ/kg.
7. Entropy
Which statement best describes the entropy change of an isolated system
undergoing an irreversible process?
A. It must decrease
B. It must remain zero
4
ENGINEERS PRINCIPLES AND PRACTICE
CHEMICAL EXAM WITH ACTUAL
QUESTIONS AND VERIFIED ANSWERS,
PLUS EXPLAINED RATIONALES/EXPERT
VERIFIED FOR GUARANTEED 100% PASS
2026/LATEST UPDATE/INSTANT
DOWNLOAD PDF
1. Material Balance — Recycle
A continuous process receives 1,000 kg/h of a feed containing 30 wt% A
and 70 wt% inert material. A separator recovers 90% of A in the product
stream. The remaining stream is recycled completely to the reactor. If
the reactor has no reaction and no accumulation, what is the approximate
fresh-feed requirement of A needed to obtain 270 kg/h of A in the
product?
A. 270 kg/h
B. 300 kg/h
C. 330 kg/h
D. 360 kg/h
Answer: B. 300 kg/h
Rationale: The separator recovers 90% of the A entering the separator.
To obtain 270 kg/h of A in the product, the total A entering the
separator must be 270/0.90 = 300 kg/h. At steady state, the recycle does
not alter the overall balance around the entire process because
internal recycle streams cancel. Therefore, the required fresh A input
is 300 kg/h.
1
,2. Stoichiometry — Limiting Reactant
A reactor performs the reaction:
2A+B→2C
A feed contains 100 mol/h of A and 80 mol/h of B. Assuming complete
conversion of the limiting reactant, what is the maximum production rate
of C?
A. 80 mol/h
B. 100 mol/h
C. 160 mol/h
D. 180 mol/h
Answer: B. 100 mol/h
Rationale: The stoichiometric requirement is 2 mol A for every 1 mol
B. For 80 mol/h of B, 160 mol/h of A would be required, but only 100
mol/h are available. Thus A is limiting. Because 2 mol A produce 2
mol C, the molar production of C equals the molar consumption of A,
giving 100 mol/h C.
3. Combustion — Excess Air
Methane is completely combusted according to:
CH4+2O2→CO2+2H2O
Air contains 21 mol% oxygen. If 25% excess air is supplied per mole of
methane, what is the approximate molar flow of air required per mole of
methane?
A. 9.52 mol
B. 10.00 mol
2
,C. 11.90 mol
D. 12.50 mol
Answer: C. 11.90 mol
Rationale: The theoretical oxygen requirement is 2 mol O₂/mol CH₄.
With 25% excess air, the actual oxygen supplied is 2(1.25) = 2.5 mol
O₂. Since air contains 0.21 mol O₂ per mole of air, the required air is
2.5/0.21 ≈ 11.90 mol air per mole CH₄.
4. Energy Balance — Sensible Heating
A process heats 5,000 kg/h of a liquid from 25°C to 85°C. The average
heat capacity is 4.0 kJ/(kg·K). Neglecting heat losses, what heat-transfer
rate is required?
A. 0.33 MW
B. 0.67 MW
C. 1.20 MW
D. 1.50 MW
Answer: B. 0.33 MW
Rationale: The heat duty is Q=m˙CpΔT. Therefore,
Q=(5,000)(4.0)(85−25)=1,200,000 kJ/h. Dividing by 3,600 s/h gives
approximately 333 kW, or 0.33 MW.
5. Thermodynamics — Ideal Gas
An ideal gas occupies 2.0 m³ at 300 K and 500 kPa absolute pressure.
What is the approximate number of kilomoles present?
Use R=8.314 kPa·m³/(kmol·K).
A. 0.20 kmol
B. 0.40 kmol
3
, C. 0.60 kmol
D. 1.20 kmol
Answer: B. 0.40 kmol
Rationale: From PV=nRT, n=PV/(RT). Substituting gives
n=(500)(2)/(8.314)(300)≈0.401 kmol. Therefore, approximately 0.40
kmol of gas is present.
6. Thermodynamics — First Law
A steady-flow compressor receives gas with negligible changes in
kinetic and potential energy. The gas enters with enthalpy of 300 kJ/kg
and exits at 500 kJ/kg. If heat loss from the compressor is 20 kJ/kg, what
shaft work input is required?
A. 180 kJ/kg
B. 200 kJ/kg
C. 220 kJ/kg
D. 520 kJ/kg
Answer: C. 220 kJ/kg
Rationale: For a compressor, the required work input is approximately
Win=Δh+Qout when kinetic and potential effects are negligible. Thus
Win=(500−300)+20=220 kJ/kg.
7. Entropy
Which statement best describes the entropy change of an isolated system
undergoing an irreversible process?
A. It must decrease
B. It must remain zero
4
