PES
S 213 General Physiics III
Practicce Exam 2
1. An infllexible contaainer with 1 liter volumee is sealed wiith 1.5 moles of an ideall gas inside at
a 20o
C and at
a 1 atmosph
here of pressure. What must
m the tem
mperature be to double thhe pressure
inside??
2. A calorrimeter is co
onstructed ussing an insullated containner and 500 grams
g
of waater [specific heat
of wateer is 4186 J/((K·kg)] initially at 20o C.
C A 100 graam ingot of copper
c
[speccific heat of 387
J/(K·kgg)] initially at
a 300o C is placed
p
into the
t calorimeter and the system
s
is alloowed to reacch
thermal equilibrium
m. Assume heat
h loss to the
t insulatedd container, thermometer
t
r, and steam is
negligible. Find th
he final tempperature afterr equilibrium
m is reached..
3. Identifyy the isobariic, isothermaal, isometric and adiabatic
processses in the diaagram to thee right. (For process
p
B, thhere is
no heatt exchange.)
4. Under 1 atm of preessure (1 atm
m = 1.013x1005 Pa), how much
m
heat iss absorbed by a 200 gram
m
block of
o frozen eth
hyl alcohol (iinitially at itss freezing pooint) to convvert it entirelly to vapor (at its
vaporizzation point))?
Mellting point off liquid ethyl alcohol at 1 atm.
Boilling point off liquid ethyll alcohol at 1 atm.
Lateent heat of fu
usion for ethhyl alcohol
Lateent heat of vaaporization for
f ethyl alcohol
Speccific heat off liquid ethyl alcohol
R. Gist
1 of 2
159 K
351 K
109 kJ/kkg
879 kJ/kkg
2.4 kJ/(kkg K)
Ver A, Reev. 2
PES 213 General Physics III
Practice Exam 2
5. A 2 mole sample of an ideal gas is subjected to compression at a constant pressure of 1.5
atmospheres from a volume of 1 liter to a volume of 0.5 liters. How much work was required
for this compression? If the temperature only rises from 20o C to 23o C during this process,
how much heat flowed out of the ideal gas? [Universal Gas Constant: R=8.314
J/(mol·K)=0.08206 L atm/(mol·K), 1 atm = 1.013x105 Pa]
6. A particular heat engine operates between two temperatures, 100 o C and 300o C. Each engine
cycle takes 0.1 seconds to complete. During each cycle, 120 J is transferred out of the hot
reservoir and 100 J is transferred into the cold reservoir. What is the efficiency of this heat
engine? What power is generated by this engine? What is the efficiency of a perfect (Carnot)
engine operating between these two reservoirs?
7. A heat pump is running as a refrigerator. It is found that for each cycle, 10 J of heat are
extracted from the cold reservoir and 15 J of heat enter the hot reservoir. What is the
coefficient of performance of this heat pump?
8. A 3 mol sample of an ideal gas at 20o C contained in a .25 L jar. The jar is then connected to a
1 L evacuated chamber (by a tube of negligible volume) and allowed to expand into the
chamber with a negligible temperature change. How much has the entropy of the universe
changed in this process? How much potential work is forever lost? [possible processes on
exam: isothermal & isobaric phase change, free expansion of ideal gas, or heat transfer from
one reservoir to another]
9. How much longer will a slot in a copper plate be if it is 2 cm at 20o C after the plate is heated
to 1000o C [Coefficient of linear thermal expansion for copper is 17x10-6 1/K]?
10. A bunker wall is constructed of concrete, an air gap, and an inner layer of steel. The concrete
wall is 8 cm thick [thermal conductivity of concrete is 0.15 W/(m·K)]. The inner wall is 1 cm
thick and made of steel [thermal conductivity=46 W/(m·K)]. The air gap between the two
walls is 1 cm wide [thermal conductivity of still air at 27o C is 0.026 W/(m·K)]. What is the
rate of heat loss through an area 4 meters by 1 meter if the interior temperature is 27o C and the
exterior temperature is 0o C?
R. Gist
2 of 2
Ver A, Rev. 2