Exam 1

Question 1

Water is in a closed system. If we know that it is at its triple point, which information will change its temperature?

A. Its specific volume
B. Its specific enthalpy
C. Its pressure
D. Any of the above
E. None of the above

Answer 1

E. none of the above.

At the triple point, temperature is fixed, and none of the listed changes will affect it while the system remains in equilibrium.

Question 2

Under which conditions are real gases most likely
to behave like ideal gases?

A. Low pressure and low temperature
B. Low pressure and high temperature
C. High pressure and low temperature
D. High pressure and high temperature
E. Ideal gases cannot approximate the
behavior of real gases under any conditions

Answer 2

B. Low P, High T

Question 3

An ideal gas is in a closed system with rigid walls.
it undergoes a process where its internal energy changes.

A. The initial and final temperatures are the same
B. The initial and final pressures are the same
C. The initial and final specific volumes are the same
D. All of the above
E. None of the above

Answer 3

C. The initial and final specific volumes are the same.

Rigid walls = it does not allow volume changes. Vi=Vf

Question 4

In the Open System Energy Balance, the kinetic
energy per unit mass is given by the term. If the units given is m2/s2, how do we convert this to
kJ/kg?

A. Multiply by 100
B. Multiply by 1,000
C. Divide by 100
D. Divide by 1,000
E. None of the above

Answer 4

D. Divide by 1,000

Question 5

Which of the following is FALSE for the enthalpy of
an ideal gas?

A. It depends on the temperature
B. It does not depend on the pressure
C. The values given in the ideal gas property tables are for constant specific heats
D. All of the above
E. None of the above

Answer 5

C. The values given in the idea gas property tables are for constant specific heats

Question 6

Superheated water at 2 MPa is in a closed system.
Which additional information will completely describe its state?

A. Its temperature
B. Its specific internal energy
C. Its specific volume
D. Any of the above
E. None of the above

Answer 6

D. Any of the above

Properties associated with superheated water vapor are found in table A-6 (v, u, h, s).

Question 7

Nitrogen gas is in a closed system with rigid walls.
Which of the following Work is NOT possible?

A. Work due to electricity
B. Pressure-volume Work
C. Work by a paddle-wheel
D. All of the above
E. None of the above

Answer 7

B. Pressure-volume Work

Rigid walls = it does not allow volume changes. Vi=Vf

Question 8

Which of the following devices mainly converts enthalpy to kinetic energy?

A. Nozzle
B. Diffuser
C. Turbine
D. Compressor
E. None of the above
Which of the following devices mainly converts enthalpy to kinetic energy?

Answer 8

A. Nozzle

Explanation:
Nozzle: converts enthalpy (thermal energy) into KE
Diffuse: Converts KE back into pressure/ enthalpy
Turbine: converts enthalpy into shaft work (mechanical energy)
Compressor: adds work to increase pressure and enthalpy. It does not convert enthalpy to KE.

Question 9

Superheated water vapor in a piston-cylinder is slowly cooled at constant pressure until it completely condenses into a saturated liquid. Which of the following is TRUE during the process?

A. The temperature of the system decreased
B. The quality goes from 1 to 0
C. The change in enthalpy is equal to the heat
lost by the system
D. All of the above
E. None of the above

Answer 9

D. All of the above

Value of quality ranges from 0 to 1, at saturated liquid states x=0.

Question 10

Why is enthalpy used in the Open System Energy Balance instead of internal energy?

A. The enthalpy and internal energy are the same for open systems
B. The enthalpy accounts for the heat transfer at constant pressure
C. The enthalpy includes the pressure-volume work at the inlet and outlet
D. All of the above
E. None of the above

Answer 10

C. The enthalpy includes the pressure-volume work at the inlet and outlet

h= u + pv

Question 11

An ideal gas in a piston-cylinder system expands from State 1 to State 2. If States 1 & 2 have the same temperature, which of the following is TRUE?

A. W is less than ΔU
B. W is equal to Q
C. The ΔH is positive
D. All of the above
E. None of the above

Answer 11

B. W is equal to Q

There is negligible changes in PE and KE, reducing the equation to the change in internal energy of the system due to heat and work

U = Q - W
if U = 0
W = Q

Question 12

Which of the following can be seen in a phase diagram of a pure substance?

A. The temperature(s) and pressure(s) where solid and vapor are in equilibrium
B. The temperature and pressure where liquid and solid have identical properties
C. Information on the quality of a mixture of saturated liquid and saturated vapor
D. All of the above
E. None of the above

Answer 12

A. The temperature(s) and pressure(s) where solid and vapor are in equilibrium

Phase diagram, p vs T (pure substance) shows all the possible states of water.

A PortraiT of the phases
Solid on the Side
Gas on the Ground
Liquid is what’s Left

Question 13

Which type of energy is NOT significant for living organisms at the nanoscale?

A. Chemical energy
B. Mechanical energy
C. Electromagnetic energy
D. Thermal energy
E. None of the above

Answer 13

E. None of the above

They are all significant.

Chemical = Internal energy
Mechanical = PE or KE
Electromagnetic = PE
Thermal = Internal energy

Question 14

A gas in a piston-cylinder expands in a quasiequilibrium process. Which of the following is TRUE?

A. The pressure of the gas is equal to the pressure of the surroundings during the entire process
B. The path of the process can be shown in a pressure vs. volume plot of the gas
C. The expansion can be described by a polytropic process
D. All of the above
E. None of the above

Answer 14

D. All of the above

The system remains nearly in thermodynamic equilibrium at all times, because of this, you can define the state of the gas at each point, and therefore the path can be plotted on a P-V diagram, can be modeled by PVn = constant.

Question 15

In the Open System Energy Balance, the kinetic energy per unit mass is given by the term v²/2. If the units for v²/2 are m²/s² and we want to convert kJ/kg to m²/s², what should be done?

A. Multiply kJ/kg by 100
B. Multiply kJ/kg by 1,000
C. Divide kJ/kg by 100
D. Divide kJ/kg by 1,000
E. None of the above

Answer 15

B. Multiply kJ/kg by 1,000

Question 16

Which of the following is TRUE for the specific internal energy of an ideal gas?

A. It depends on the temperature
B. It does not depend on the pressure
C. The values given in the ideal gas property tables are for specific heats that vary with temperature
D. All of the above
E. None of the above

Answer 16

D. All of the above

Question 17

Which of the following CANNOT be seen in a phase diagram of a pure substance?

A. The temperature and pressure where liquid and vapor have identical properties
B. Information on whether the solid is less dense than the liquid
C. Information on the quality of a mixture of saturated liquid and saturated vapor
D. All of the above
E. None of the above

Answer 17

C. Information on the quality of a mixture of saturated liquid and saturated vapor

Question 18

Carbon dioxide gas is in a closed system with non-rigid walls. Which of the following work interaction(s) with the surroundings is (are) possible?

A. Work due to electricity
B. Pressure-volume work
C. Work by a paddle-wheel
D. All of the above
E. None of the above

Answer 18

D. All of the above

Question 19

Why is enthalpy used in the Open System Energy Balance instead of internal energy?

A. The enthalpy and internal energy are the same for open systems
B. The enthalpy accounts for the heat transfer at constant pressure
C. The enthalpy includes the shaft work within the control volume
D. All of the above
E. None of the above

Answer 19

E. None of the above

Question 20

Saturated water vapor in a piston-cylinder is cooled at constant pressure until it has a quality of 0.4. If the system is closed, which of the following is TRUE?

A. At the final state, the mass of liquid water is less than the mass of water vapor
B. The change in internal energy of the system is equal to the heat exchanged with the surroundings
C. The specific volume of the entire system at the final state is greater than that of the saturated liquid but less than that of the saturated vapor at the same temperature and pressure
D. All of the above
E. None of the above

Answer 20

C. The specific volume of the entire system at the final state is greater than that of the saturated liquid but less than that of the saturated vapor at the same temperature and pressure

Question 21

An ideal gas is in a closed system with rigid walls. It undergoes a process from State 1 to State 2 where its temperature changes. Which of the following is TRUE?

A. The initial and final specific internal energies are equal
B. The initial and final specific enthalpies are not equal
C. The initial and final pressures are equal
D. All of the above
E. None of the above

Answer 21

B. The initial and final specific enthalpies are not equal

Question 22

Which of the following devices mainly converts work to enthalpy?

A. Diffuser
B. Nozzle
C. Compressor
D. Turbine
E. None of the above

Answer 22

C. Compressor

Question 23

Under which conditions would using the Table of properties for air as an ideal gas give the least error?

A. Low pressure and high temperature
B. Low pressure and low temperature
C. High pressure and high temperature
D. High pressure and low temperature
E. Not enough information is given to answer the question

Answer 23

A. Low pressure and high temperature

Question 24

An ideal gas in a piston-cylinder assembly (closed system) is compressed from State 1 to State 2. If States 1 & 2 have the same temperature but different pressures, which of the following is TRUE?

A. Q is less than W
B. W is less than ΔU (consider the sign of W)
C. ΔH is equal to Q
D. All of the above
E. None of the above

Answer 24

B. W is less than ΔU (consider the sign of W)

Question 25

Water is in a closed system at 150 kPa. If we know that it has a quality of 0.75, what additional information will completely describe its state? A. Its temperature B. Its specific internal energy C. Its specific volume D. Any of the above E. None of the above

Answer 25

E. None of the above

Question 26

A closed system can go from State 1 to State 2 using different processes. Which of the following is always TRUE whenever the system goes from State 1 to State 2? A. The work involved is always the same B. The heat involved is always the same C. The change in internal energy is always the same D. All of the above E. None of the above

Answer 26

C. The change in internal energy is always the same

Question 27

Inside the cell, most processes happen at the nanometer scale. At this scale, which of the following is TRUE about the forms of energy in the cell? A. Chemical energy is the most dominant B. Mechanical energy is the most dominant C. Thermal energy is the most dominant D. Electromagnetic energy is the most dominant E. None of the above

Answer 27

E. None of the above

Question 28

Water is in a closed system. If we know that it is at its triple point, which of the following is FALSE? A. Its temperature is set B. Its pressure is set C. Its degree of freedom is one (from the phase rule) D. All of the above E. None of the above

Answer 28

C. Its degree of freedom is one (from the phase rule)

Question 29

An ideal gas in a piston-cylinder system (closed system) undergoes a process from State 1 to State 2. States 1 & 2 have different temperatures, pressures, and volumes. If the specific heats of the ideal gas are constant during the process, which one is FALSE regarding the ΔU for the process? A. ΔU = m·cv·(T₂ − T₁) B. ΔU = m·cp·(T₂ − T₁) C. ΔU = Q − W D. All of the above E. None of the above

Answer 29

B. ΔU = m·cp·(T₂ − T₁)