PHYS-1401: College Physics-I
CRN 55178
Khalid Bukhari
HW-12
HOMEWORK PROBLEMS Chapter 12: THE LAWS OF THERMODYNAMICS
PART-A: Hand in your answers in class on scantron on Monday 06 Dec-2010. Write your name,
class (1401) and HW # 12 on the scantron.
1.
An ideal gas is maintained at a constant pressure of 70.0 kPa during an isobaric process
while its volume decreases by 0.20 m3. What is the work done by the system on its environment?
(a) 14 kJ
(b) 35 kJ
(c) −14 kJ
(d) −35 kJ
(e) −72 kJ
2.
A 2.0-mole ideal gas system is maintained at a constant volume of 4.0 liters. If 100 J of
thermal energy is transferred to the system, what is the change in the internal energy of the
system?
(a) 0 (b) 400 J
(c) 70 J
(d) 100 J
(e) −0.100 J
3.
A monatomic ideal gas expands from 1.00 m3 to 2.50 m3 at a constant pressure of 2.00 X
105 Pa. Find the change in the internal energy of the gas.
(a) 7.50 X 105 J
(b) 1.05 X 106 J
(c) 4.50 X 105 J
(d) 3.00 X 105 J
4.
An ideal gas drives a piston as it expands from 1.00 m3 to 2.00 m3 at a constant
temperature of 850 K. If there are 390 moles of gas in the piston, how much work does the gas
do in displacing the piston?
(a) 1.9 X 106 J
(b) 2.5 X 106 J
(c) 4.7 X 106 J
(d) 2.1 X 105 J
5.
A diatomic ideal gas expands adiabatically from a volume of 1.00 m3 to a final volume of
3.50 m3. If the initial pressure is 1.00 X 105 Pa, what is the final pressure?
(a) 6.62 X 104 Pa
(b) 1.24 X 105 Pa
(c) 3.54 X 104 Pa
(d) 1.73 X 104 Pa
1
PHYS-1401: College Physics-I
CRN 55178
Khalid Bukhari
HW-12
6.
How much net work is done by the gas undergoing the cyclic process illustrated in Figure
MCQ12.6? Choose the best estimate.
(a) 1 X 105 J (b) 2 X 105 J (c) 3 X 105 J (d) 4 X 105 J (e) 5 X 105 Pa
7.
An engine does 15 kJ of work while rejecting 37 kJ to the cold reservoir. What is the
efficiency of the engine?
(a) 0.15
(b) 0.29
(c) 0.33
(d) 0.45
(e) 1.2
8.
A refrigerator does 18 kJ of work while moving 115 kJ of thermal energy from inside the
refrigerator. What is its coefficient of performance?
(a) 3.4
(b) 2.8
(c) 8.9
(d) 6.4
(e) 5.2
9.
A steam turbine operates at a boiler temperature of 450 K and an exhaust temperature of
3.0 X 102 K. What is the maximum theoretical efficiency of this system?
(a) 0.24
(b) 0.50
(c) 0.33
(d) 0.67
(e) 0.15
10.
A 1.00-kg block of ice at 0° C and 1.0 atm melts completely to water at 0°C. Calculate
the change of the entropy of the ice during the melting process. (For ice, Lf = 3.33 X 105 J/kg.)
(a) 3 340 J/K (b) 2 170 J/K
(c) −3 340 J/K
(d) 1 220 J/K
(e) −1 220 J/K
2
PHYS-1401: College Physics-I
CRN 55178
Khalid Bukhari
HW-12
11.
If an ideal gas is compressed isothermally, which of the following statements is true? (a)
Energy is transferred to the gas by heat. (b) No work is done on the gas. (c) The temperature of
the gas increases. (d) The internal energy of the gas remains constant. (e) The pressure remains
constant.
12.
When an ideal gas undergoes an adiabatic expansion, which of the following statements
is true? (a) The temperature of the gas doesn’t change. (b) No work is done by the gas. (c) No
energy is delivered to the gas by heat. (d) The internal energy of the gas doesn’t change. (e) The
pressure increases.
13.
If an ideal gas undergoes an isobaric process, which of the following statements is true?
(a) The temperature of the gas doesn’t change. (b) Work is done on or by the gas. (c) No energy
is transferred by heat to or from the gas. (d) The volume of the gas remains the same. (e) The
pressure of the gas decreases uniformly.
14.
Of the following, which is not a statement of the second law of thermodynamics? (a) No
heat engine operating in a cycle can absorb energy from a reservoir and use it entirely to do
work. (b) No real engine operating between two energy reservoirs can be more efficient than a
Carnot engine operating between the same two reservoirs. (c) When a system undergoes a
change in state, the change in the internal energy of the system is the sum of the energy
transferred to the system by heat and the work done on the system. (d) The entropy of the
Universe increases in all natural processes. (e) In all real processes, the resulting energy available
for doing work decreases.
15.
If an ideal gas is compressed to half its initial volume, which of the following statements
is true regarding the work done on the gas? (a) The isothermal process involves the most work.
(b) The adiabatic process involves the most work. (c) The isobaric process involves the most
work. (d) The isovolumetric process involves the most work. (e) The work done is independent
of the process.
16.
A window air conditioner is placed on a table inside a well-insulated apartment, plugged
in and turned on. What happens to the average temperature of the apartment? (a) It increases. (b)
It decreases. (c) It remains constant. (d) It increases until the unit warms up and then decreases.
(e) The answer depends on the initial temperature of the apartment.
17.
The second law of thermodynamics implies that the coefficient of performance of a
refrigerator must be what? (a) less than 1 (b) less than or equal to 1 (c) greater than or equal to 1
(d) finite (e) greater than 0
3
PHYS-1401: College Physics-I
CRN 55178
Khalid Bukhari
HW-12
18.
A thermodynamic process occurs in which the entropy of a system changes by −6 J/K.
According to the second law of thermodynamics, what can you conclude about the entropy
change of the environment? (a) It must be +6 J/K or less. (b) It must be equal to 6 J/K. (c) It must
be between 6 J/K and 0. (d) It must be 0. (e) It must be +6 J/K or more.
19
A gas changes in volume from 0.750 m3 to 0.250 m3 at a constant pressure of 1.50 X 105
Pa. (a) How much work is done on the gas?
(a) 7.50 x104 J
(b) 5.50 x104 J
(c) 3.50 x104 J
(d) 1.50 x104 J
20.
A thermodynamic system undergoes a process in which its internal energy decreases by
500 J. If at the same time 220 J of work is done on the system, find the energy transferred to or
from it by heat.
(a) -750 J
(b) -550 J
(c) -720 J
(d) -580 J
21.
A heat engine operates between a reservoir at 25° C and one at 375° C. What is the
maximum efficiency possible for this engine?
(a) 32 %
(b) 38 %
(c) 54 %
(d) 65 %
22.
A heat engine is being designed to have a Carnot efficiency of 65% when operating
between two heat reservoirs. (a) If the temperature of the cold reservoir is 20° C, what must be
the temperature of the hot reservoir?
(a) 564 C
(b) 438 C
(c) 862 C
(d) 485 C
4