CHE 302 (Fall 97)
__________________
LAST NAME, FIRST
Quiz #1
(Closed notes and closed books, 35 minutes)
1. A. Temperature and pressure are sometimes extensive properties of a system.
B. An adiabatic wall prevents energy transfer as heat but not as work.
1. A and B are true
2. Only A is true 3. Only B is true
4. A and B are false
2. A. An isolated system has a boundary which allows only a particular energy interaction
with its environment.
B. A steady-state open system is an example of a system that is at equilibrium.
1. A and B are true
2. Only A is true 3. Only B is true
4. A and B are false
3. One gram mole of a gas at a temperature of 25oC and a pressure of 1 bar is compressed to 10
bar by a process in which PVg = constant, where g = CP/CV. Determine:
a. (5 pts) The work required.
b. (5 pts) The change in internal energy of the gas.
Gas is ideal with CP = 38 J/mol.oK. Gas constant R = 8.314 J/mol.oK.
4. (6 pts) A 4 m3 well-insulated storage tank containing 2 m3 of liquid is to be pressurized
adiabatically with air from a large, high pressure reservoir through a valve at the top of the tank
to permit rapid ejection of the liquid. The air in the reservoir is maintained at 100 bar and 300oK.
The gas space above the liquid contains initially air at 1 bar and 280oK. When the pressure in the
tank reaches 5 bar and the liquid transfer valve is still closed, what is the air temperature? Air is
an ideal gas with CP = 38 J/mol.oK. Gas constant R = 8.314 J/mol.oK
CHE 302 (Fall 97)
__________________
LAST NAME, FIRST
Quiz #2
(Closed notes and closed books, 35 minutes)
1. A. At constant pressure, enthalpy change for a closed system equals the heat effect for a
reversible process doing PV work.
B. Cp for an ideal gas is independent of temperature.
1. A and B are true
2. Only A is true 3. Only B is true
4. A and B are false
2. A rigid tank 3 m3 in total volume initially contains 1200 kg of saturated liquid water; the
remainder of the volume is filled with saturated vapor steam. The initial temperature is 200oC; at
that time 800 kg of liquid water at 60oC are added to the tank, along with enough heat to keep the
temperature at 200oC. Steam still presents at the end of the process.
2a) A. The initial specific properties of the saturated water and steam can be determined from
the steam table.
B. The initial and final specific properties of the saturated water and steam are the same.
1. A and B are true
2. Only A is true 3. Only B is true
4. A and B are false
2b) (4 pts) The initial specific volumes of saturate water and steam are: Vl = 1.157x10-3 m3/kg,
Vv = 127.4x10-3 m3/kg. Determine the inital vapor mass in kg.
3.
a) (6 pts) Calculate the minimum amount of work required to cool 1 mol of oxygen gas at
o
298 K and 1 atm to 90.13oK in a reversible isobaric process in which heat is transferred to a heat
reservoir at 298oK.
b) (6 pts) Calculate the minimum amount of work required to convert 1 mol of oxygen gas
at 298oK and 1 atm to the liquid state at 90.13oK (the atmospheric boiling point) in a reversible
isobaric process in which heat is transferred to a heat reservoir at 298oK.
Data for 3a and 3b:
For oxygen gas: Cp = 6.96 cal/mol.oK, heat of vaporization at 90.13oK = 1628.8 cal/mol.
CHE 302 (Fall 97)
1.
__________________
LAST NAME, FIRST
Quiz #3
(Closed notes and closed books, 35 minutes)
A. The absolute value of internal energy can be determined experimentally.
B. In an adiabatic closed system, the entropy change for some process may be less than
zero.
1. A and B are true
2. Only A is true 3. Only B is true
4. A and B are false
A. The area under the T-S diagram path is the reversible heat exchange.
B. The entropy change for an irreversible process between states A and B is different from
the entropy change for a reversible process between states A and B.
1. A and B are true
2. Only A is true 3. Only B is true
4. A and B are false
2.
3. (8 pts) A block of polymer weighing 150 g is to be compressed from a pressure of 1 atm to a
pressure of 1501 atm. Assume that the volume of the polymer does not change much during the
compression, determine the heat in J required (added or removed) to maintain the polymer at a
constant temperature of 300oK. Data: 1 atm = 1.013x105 Pa.
1  V 
For polymer: density = 1.2 g/m3, v =

 = 8.5x10-7 K-1.
V  T  P
4. (8 pts) A steady stream of air at 300oF and 5 atm is available. How much work can be obtained
from each lbmol of air if it flow through a reversible device and leaves at 77oF and 1 atm? The
device may exchange heat with the surroundings at 77oF. Assume ideal gas behavior and
constant heat capacity (Cp = 7.0 Btu/lbmol.oR, gas constant R = 1.987 Btu/lbmol.oR)
CHE 302 (Fall 97)
__________________
LAST NAME, FIRST
Quiz #4
(Closed notes and closed books, 35 minutes)
Note: Your answers must be correct to 3 significant figures and have the appropriate units.
1. A. In a closed system at constant T and P, a spontaneous process will increase Gibbs free
energy, G, until a maximum value for G is reached at equilibrium.
B. Chemical potential is an intensive property.
1. A and B are true
2. Only A is true 3. Only B is true
4. A and B are false
2. A. The size and thermodynamic state of a pure single phase system would be fixed by two of
its intensive state variables.
B. The chemical potential of a pure substance is equal to its specific Gibbs free energy, G.
1. A and B are true
2. Only A is true 3. Only B is true
4. A and B are false
 U 
3. A. P = 

 V  S
1. A and B are true
 U 
B. T = 

 S V
2. Only A is true 3. Only B is true
4. A and B are false
4. A. Entropy change of matter from (T1, V1) to (T2, V2) can be determined from
C
P
dS = V dT +
dV
T
T
B. Entropy change of matter from (T1, P1) to (T2, P2) can be determined from
C
P
dS = P dT +
dV
T
T
1. A and B are true
2. Only A is true 3. Only B is true
4. A and B are false
5. (8 pts) 20 g of water at 0oC is placed in a large cold space (a reservoir) at - 15oC until it
completely freezes (still at 0oC). The heat of fusion of water at 0oC is -335 J/g.
a. The entropy change of the water is
__________
b. The entropy change of the surrounding is
__________
o
.o
If the final state is ice at -15 C and CP,ice = 2.1 J/g K.
c. The entropy change of the water is
__________
d. The entropy change of the surrounding is
__________
6. (4 pts) Determine volume of pure water at 25oC required to form 200 cm3 of 72.2 mole %
solution of water in methanol.
Data: Water (1) V1 (at x1 = 0.722) = 17.840 cc/mol, V1 = 18.0686 cc/mol
Methanol (2) V2 (at x1 = 0.722) = 38.486 cc/mol, V2 = 40.7221 cc/mol
V1 =
____________
CHE 302 (Fall 97)
__________________
LAST NAME, FIRST
Quiz #5
(Closed notes and closed books, 35 minutes)
Note: Your answers must be correct to 3 significant figures and have the appropriate units.
I. Crystalline sodium sulfate, in the presence of water vapor, may form a decahydrate.
Na2SO4(s) + 10H2O(g) = Na2SO4.10H2O(s)
(1)
Data: (Note: R = 1.987 cal/mol.oK)
Species
∆Hf(25oC), kcal/mol
Na2SO4(s)
- 330.50
H2O(g)
- 57.798
Na2SO4.10H2O(s)
- 1033.85
∆Gf(25oC), kcal/mol
- 302.33
- 54.635
- 870.52
a. The standard heat of reaction at 25oC for reaction (1) is
__________
b. The standard Gibbs free energy change at 25oC for reaction (1) is
__________
c. If ∆Grxn(25oC) = - 25.7 kcal/mol, Ka (at 25oC) is
__________
d. If ∆Hrxn = -200 kcal/mol = constant, Ka = 1.21012 at 300oK, Ka at 280oK is
 (ln K a ) H rxn
Note:
=
RT 2
T
__________
e. If Ka (at 25oC) = 2.5x1012, the partial pressure of water at equilibrium is
__________
II. A heat engine operating between reservoirs at 1100oK and 300oK is found to deliver 1200
J/hr of work with 2100 J/hr of high-temperature heat absorbed.
a. The heat dumped to the low-temperature sink in J/hr is
__________
b. The maximum work that could be obtained from the engine is
__________
c. The entropy production in J/hr.oK is
__________
III. Nitrogen gas flowing at the rate of 1200 kg/h enters a compressor at 1 bar and 300oK and
leaves at 12 bar and 450oK. Cooling water enters the compressor at 300oK and leaves at 350oK.
Cooling water flow rate is 1500 kg/hr. Nitrogen (MW = 28) is an ideal gas with Cp = 1.05
kJ/kg.oK. Heat capacity of water is 4.184 kJ/kg.oK. Gas constant R = 8.314 J/mol.oK.
a. The entropy change of nitrogen is
__________
b. The entropy change of water is
__________
CHE 302 (Fall 97)
_______________________
LAST NAME, FIRST (8 pts)
Final Exam (Closed notes and closed books)
(Note: Your numerial answers must be correct to 3 significant figures. There are 26 questions with 4
points each, however you can only obtain a maximum of 100 points. That means you can miss 3
questions and still get 100% score.).
1. Consider the following gas phase reaction (Note: R = 8.314 J/mol.oK)
C3H8 + 3H2O = 3CO + 7H2
(1)
Data
Species
C3H8
H2O
CO
H2
∆Hf(25oC), kcal/mol
- 24.82
- 57.798
- 26.416
0
∆Gf(25oC), kcal/mol
- 5.614
- 54.635
- 32.808
0
a. The standard heat of reaction at 25oC for reaction (1) is
b. The standard Gibbs free energy change at 25oC for reaction (1) is
c. If ∆Grxn(975oK) = - 195.74 kJ/mol, Ka (at 975oK) is __________
d. If ∆Hrxn = 530 kJ/mol = constant, Ka = 82.1 at 750oK, Ka at 900oK is
 (ln K a ) H rxn
Note:
=
RT 2
T
e. When 0.6 mole of C3H8 has reacted, the mole fraction of CO is
f. When 0.6 mole of C3H8 has reacted, the mole fraction of C3H8 is
Inital moles
2
3
0
0
__________
__________
__________
__________
__________
2. A heat engine operating between reservoirs at 1000oK and 300oK is found to deliver 1100 J/hr
of work with 2000 J/hr of high-temperature heat absorbed.
a. The heat dumped to the low-temperature sink in J/hr is
__________
b. The maximum work that could be obtained from the engine is
__________
c. The entropy production in J/hr.oK is
__________
3. Nitrogen gas flowing at the rate of 800 kg/h enters a compressor at 1 bar and 300oK and leaves
at 12 bar and 450oK. Cooling water enters the compressor at 300oK and leaves at 340oK.
Cooling water flow rate is 1,000 kg/hr. Nitrogen (MW = 28) is an ideal gas with Cp = 1.05
kJ/kg.oK. Heat capacity of water is 4.184 kJ/kg.oK. Gas constant R = 8.314 J/mol.oK.
a. The entropy change of nitrogen is
b. The entropy change of water is
__________
c. The work provided by the compressor is
__________
d. If the entire process is reversible, the temperature of the exit water is
__________
__________
4. A block of polymer weighing 100 g is to be compressed from a pressure of 1 atm to a pressure
of 1501 atm. The volume of the polymer does not change much during the compression. The
polymer is maintained at a constant temperature of 300oK. Data: 1 atm = 1.013x105 Pa.
1  V 
For polymer: density = 1.1 g/cm3, v =

 = 6.510-7 K-1.
V  T  P
The entropy change of polymer is
__________
5. The following closed-loop steam cycle has been proposed to generate work from burning fuel.
Q
Boiler
Pump
W
T urbine
Wn et
Condenser
Q
The temperature of the burning fuel is 1100oC, and cooling water is available at 15oC. The steam
leaving the boiler is at 20 bar and 700oC, and the condenser produces a saturated liquid at 0.2
bar. The steam lines are well insulated, the turbine and pump operate reversibly and adiabatically,
and some of the mechanical work generated by the turbine is used to drive the pump. The steam
leaving the turbine is superheated vapor and the steam leaving the condenser is saturated liquid.
Your numerial answers must be correct to 4 significant figures for problem 5.
Data:
T(oC)
700
60.1
67
60.1
P(bar)
20
20
0.2
0.2
H(kJ/kg)
3917.4
254.3
2623.2
251.4
S(kJ/kg.oK)
7.9487
0.8320
7.9487
0.8320
V(m3/kg)
0.00102
a. The work supplied by the turbine per kg of steam generated in the boiler is __________
b. Heat discarded in the condenser per kg of steam generated in the boiler is
__________
c. The work used by the pump per kg of steam generated in the boiler is
__________
d. Heat absorbed in the boiler per kg of steam generated is
__________
e. The efficiency of a Carnot cycle operated at this cycle temperature range is __________
f. A. The fluid leaving the pump is saturated liquid.
B. There is no change in entropy across the turbine.
1. A and B are true 2. Only A is true
3. Only B is true
4. A and B are false
6. Consider a pure material with N moles
A. (∂U/∂N) at constant S and V = 0
B. (∂U/∂N) at constant S and V = (∂U/∂N) at constant S and V
1. A and B are true 2. Only A is true
3. Only B is true
4. A and B are false
7. Consider 500 cm3 of 72.2 mole % solution of water in methanol.
Data: Water (1) V1 (at x1 = 0.722) = 17.840 cc/mol, V1 = 18.0686 cc/mol
Methanol (2) V2 (at x1 = 0.722) = 38.486 cc/mol, V2 = 40.7221 cc/mol
Moles of water in the solution is
__________
8. A strong capillary tube filled with mercury and closed initially at 20oC and 1 atm is heated to
1  V 
1  V 
25oC at constant volume. For mercury v =

 = 16x10-5 K-1 and  =  
 =
V  T  P
V  P T
3.5x10-6 atm-1. The resulting pressure is
__________
9. One of the processes in our plant uses ammonia as a raw material. It is stored as a saturated
liquid at 77oF and is vaporized in a steam-heated heat exchanger and then expanded through a
turbine before being fed into the process at essentially atmospheric pressure. The exhaust from
the turbine should be saturated vapor at 15 psia and the turbine is assumed to be both reversible
and adiabatic.
a. The temperature of the ammonia vapor prior to entering the turbine is
A) 210oF
B) 250oF
C) 290oF
b. Work available from the turbine in Btu per lb of ammonia is
A) 140
B) 180
C) 220
c. Heat added in the heat exchanger in Btu per lb of ammonia is
A) 490
B) 530
C) 570
D) 330oF
D) 260
D) 610
Figure 1. Temperature-entropy diagram for ammonia