Oregon Chemical Engineering Exam
Practice Questions And Correct Answers
(Verified Answers) Plus Rationale 2027
Q&A| Instant Download Pdf.
1. A chemical engineering process is operating at steady state with no
accumulation of material in the system. Which statement correctly describes
the overall material balance?
A. Input must equal output plus accumulation
B. Input must equal output when accumulation is zero
C. Output must always exceed input
D. Input and output are unrelated at steady state
Rationale: At steady state, accumulation is zero, so the overall material
balance reduces to total input equaling total output when there are no
other sources or sinks.
2. A process stream contains 40 kg of ethanol and 60 kg of water. What
is the mass fraction of ethanol in the stream?
A. 0.20
B. 0.40
C. 0.60
D. 0.67
Rationale: Mass fraction equals the component mass divided by total
mixture mass, so 40/(40+60)=0.4040/(40+60)=0.40.
, 3. A liquid mixture contains 25 mol of component A and 75 mol of
component B. What is the mole fraction of component A?
A. 0.20
B. 0.25
C. 0.50
D. 0.75
Rationale: Mole fraction is the number of moles of the component divided
by the total number of moles, giving 25/(25+75)=0.2525/(25+75)=0.25.
4. A gas mixture contains 30 mol% oxygen and 70 mol% nitrogen at a
total pressure of 500 kPa. Assuming ideal-gas behavior, what is the
partial pressure of oxygen?
A. 50 kPa
B. 100 kPa
C. 150 kPa
D. 350 kPa
Rationale: Dalton’s law gives the oxygen partial pressure as
yO2P=0.30(500)=150y_{O_2}P=0.30(500)=150 kPa.
5. An ideal gas is compressed at constant temperature while the number
of moles remains unchanged. What happens to its pressure when its
volume is reduced?
A. Pressure decreases
B. Pressure remains constant
C. Pressure increases
D. Pressure becomes zero
Rationale: From the ideal-gas relationship PV=nRTPV=nRT, pressure is
inversely proportional to volume when temperature and moles are
constant.
, 6. A gas occupies 2.0 m³ at 300 K and constant pressure. If its
temperature increases to 450 K, what is its approximate new volume?
A. 1.33 m³
B. 2.00 m³
C. 3.00 m³
D. 4.50 m³
Rationale: At constant pressure, Charles’s law gives
V2=V1(T2/T1)=2(450/300)=3.0V_2=V_1(T_2/T_1)=2(450/300)=3.0 m³.
7. A chemical process heats a liquid from 20°C to 80°C. If the specific
heat is approximately constant, which relationship determines the
sensible heat required?
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/ΔTQ=mC_p/\Delta T
Rationale: Sensible heat for a constant-specific-heat material is calculated
as Q=mCpΔTQ=mC_p\Delta T.
8. A reactor releases heat during an exothermic reaction. Which process
condition generally requires careful control to prevent excessive
temperature rise?
A. Heat-removal capacity
B. Molecular weight alone
C. Pipe color
D. Ambient pressure only
Rationale: Exothermic reactions generate heat, so adequate heat removal
and temperature control are essential to prevent thermal runaway or
unsafe operating conditions.
, 9. In thermodynamics, the first law of thermodynamics is fundamentally
a statement of what principle?
A. Conservation of energy
B. Conservation of mass only
C. Conservation of momentum only
D. Conservation of entropy as exactly zero
Rationale: The first law states that energy is conserved and relates heat,
work, and changes in system energy.
10. A closed system receives 500 kJ of heat and performs 200 kJ of
work on its surroundings, with negligible changes in kinetic and
potential energy. What is the approximate change in internal energy?
A. 300 kJ increase
B. 300 kJ decrease
C. 700 kJ increase
D. 700 kJ decrease
Rationale: Using ΔU=Q−W\Delta U=Q-W, the internal-energy change is
500−200=300500-200=300 kJ.
11. The second law of thermodynamics introduces the concept of
entropy. Which statement is generally correct for an isolated system?
A. Entropy cannot decrease
B. Entropy must always equal zero
C. Entropy decreases during every spontaneous process
D. Entropy is unrelated to irreversibility
Rationale: The entropy of an isolated system remains constant for an ideal
reversible process and increases for an irreversible spontaneous process.
12. A heat engine receives energy from a high-temperature source
and rejects some energy to a low-temperature sink. Why can a real
Practice Questions And Correct Answers
(Verified Answers) Plus Rationale 2027
Q&A| Instant Download Pdf.
1. A chemical engineering process is operating at steady state with no
accumulation of material in the system. Which statement correctly describes
the overall material balance?
A. Input must equal output plus accumulation
B. Input must equal output when accumulation is zero
C. Output must always exceed input
D. Input and output are unrelated at steady state
Rationale: At steady state, accumulation is zero, so the overall material
balance reduces to total input equaling total output when there are no
other sources or sinks.
2. A process stream contains 40 kg of ethanol and 60 kg of water. What
is the mass fraction of ethanol in the stream?
A. 0.20
B. 0.40
C. 0.60
D. 0.67
Rationale: Mass fraction equals the component mass divided by total
mixture mass, so 40/(40+60)=0.4040/(40+60)=0.40.
, 3. A liquid mixture contains 25 mol of component A and 75 mol of
component B. What is the mole fraction of component A?
A. 0.20
B. 0.25
C. 0.50
D. 0.75
Rationale: Mole fraction is the number of moles of the component divided
by the total number of moles, giving 25/(25+75)=0.2525/(25+75)=0.25.
4. A gas mixture contains 30 mol% oxygen and 70 mol% nitrogen at a
total pressure of 500 kPa. Assuming ideal-gas behavior, what is the
partial pressure of oxygen?
A. 50 kPa
B. 100 kPa
C. 150 kPa
D. 350 kPa
Rationale: Dalton’s law gives the oxygen partial pressure as
yO2P=0.30(500)=150y_{O_2}P=0.30(500)=150 kPa.
5. An ideal gas is compressed at constant temperature while the number
of moles remains unchanged. What happens to its pressure when its
volume is reduced?
A. Pressure decreases
B. Pressure remains constant
C. Pressure increases
D. Pressure becomes zero
Rationale: From the ideal-gas relationship PV=nRTPV=nRT, pressure is
inversely proportional to volume when temperature and moles are
constant.
, 6. A gas occupies 2.0 m³ at 300 K and constant pressure. If its
temperature increases to 450 K, what is its approximate new volume?
A. 1.33 m³
B. 2.00 m³
C. 3.00 m³
D. 4.50 m³
Rationale: At constant pressure, Charles’s law gives
V2=V1(T2/T1)=2(450/300)=3.0V_2=V_1(T_2/T_1)=2(450/300)=3.0 m³.
7. A chemical process heats a liquid from 20°C to 80°C. If the specific
heat is approximately constant, which relationship determines the
sensible heat required?
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/ΔTQ=mC_p/\Delta T
Rationale: Sensible heat for a constant-specific-heat material is calculated
as Q=mCpΔTQ=mC_p\Delta T.
8. A reactor releases heat during an exothermic reaction. Which process
condition generally requires careful control to prevent excessive
temperature rise?
A. Heat-removal capacity
B. Molecular weight alone
C. Pipe color
D. Ambient pressure only
Rationale: Exothermic reactions generate heat, so adequate heat removal
and temperature control are essential to prevent thermal runaway or
unsafe operating conditions.
, 9. In thermodynamics, the first law of thermodynamics is fundamentally
a statement of what principle?
A. Conservation of energy
B. Conservation of mass only
C. Conservation of momentum only
D. Conservation of entropy as exactly zero
Rationale: The first law states that energy is conserved and relates heat,
work, and changes in system energy.
10. A closed system receives 500 kJ of heat and performs 200 kJ of
work on its surroundings, with negligible changes in kinetic and
potential energy. What is the approximate change in internal energy?
A. 300 kJ increase
B. 300 kJ decrease
C. 700 kJ increase
D. 700 kJ decrease
Rationale: Using ΔU=Q−W\Delta U=Q-W, the internal-energy change is
500−200=300500-200=300 kJ.
11. The second law of thermodynamics introduces the concept of
entropy. Which statement is generally correct for an isolated system?
A. Entropy cannot decrease
B. Entropy must always equal zero
C. Entropy decreases during every spontaneous process
D. Entropy is unrelated to irreversibility
Rationale: The entropy of an isolated system remains constant for an ideal
reversible process and increases for an irreversible spontaneous process.
12. A heat engine receives energy from a high-temperature source
and rejects some energy to a low-temperature sink. Why can a real
