PAPP Chapter 11: Thermodynamics

Multiple Choice (75)

Identify the letter of the choice that best completes the statement or answers the question. Carefully mark your scantron answer document.

1. A 2 mol ideal gas system is maintained at a constant volume of 4 L. If the pressure is constant, how much work is done by the system?

a.	0 J	c.	8 J
b.	5 J	d.	30 J

2. According to the first law of thermodynamics, the difference between energy transferred to or from a system as heat and energy transferred to or from a system by work is equivalent to which of the following?

a.	entropy change	c.	temperature change
b.	internal energy change	d.	specific heat

3. According to the second law of thermodynamics, the heat received by a heat engine operating in a complete cycle from a high-temperature reservoir

a.	must be completely converted to work.
b.	equals the entropy increase.
c.	can be completely converted to internal energy.
d.	cannot be completely converted to work.

4. A chunk of ice with a mass of 1 kg at 0°C melts and absorbs 3.35 ´ 10⁸ J of heat in the process. Which best describes what happened to this system?

a.	Its entropy increased.	c.	Internal energy remained constant
b.	Its entropy decreased.	d.	Work was converted to energy.

5. Sunlight strikes an ice cube at its melting point and causes it to melt. What is this process?

a.	adiabatic process	c.	isobaric process
b.	isothermal process	d.	isovolumetric process

6. How is conservation of internal energy expressed for an isothermal system?

a.	Q = W = 0, so DU = 0 and Ui = Uf
b.	Q = 0, so DU = –W
c.	DT = 0, so DU = 0; therefore, DU = Q – W = 0, or Q = W
d.	DV = 0, so PDV = 0 and W = 0; therefore, DU = Q

7. A thermodynamic process occurs, and the entropy of a system decreases. What can be concluded about the entropy change of the environment?

a.	It decreases.
b.	It increases.
c.	It stays the same.
d.	It could increase or decrease, depending on the process.

8. How is conservation of internal energy expressed for an isovolumetric system?

a.	Q = W = 0, so DU = 0 and Ui = Uf
b.	Q = 0, so DU = –W
c.	DT = 0, so DU = 0; therefore, DU = Q – W = 0, or Q = W
d.	DV = 0, so PDV = 0 and W = 0; therefore, DU = Q

9. Which equation describes a process that takes place at constant volume so that no work is done on or by the system?

a.	DU = Q - W	c.	DU = - W
b.	Q = W	d.	DU = Q

10. A heat engine performs 2000.0 J of net work while adding 5000.0 J of heat to the cold-temperature reservoir. What is the efficiency of the engine?

a.	71.4%	c.	40.0%
b.	60.0%	d.	28.6%

11. Which of the following processes for an ideal gas system has an unchanging internal energy and a heat intake that corresponds to the value of the work done by the system?

a.	isothermal process	c.	adiabatic process
b.	isobaric process	d.	isovolumetric process

12. A 4 mol ideal gas system undergoes an adiabatic process in which it expands and does 20 J of work on its environment. How much energy is transferred to the system as heat?

a.	–20 J	c.	5 J
b.	0 J	d.	20 J

13. A 4 mol ideal gas system undergoes an adiabatic process in which it expands and does 20 J of work on its environment. What is its change in internal energy?

a.	–20 J	c.	0 J
b.	–5 J	d.	20 J

14. When all the entropy changes in a process are taken into account,

a.	DS = 0
b.	S2 > S1
c.	S2 < S1
d.	S2 = S1

15. How is conservation of internal energy expressed for an adiabatic system?

a.	Q = W = 0, so DU = 0 and Ui = Uf
b.	Q = 0, so DU = –W
c.	DT = 0, so DU = 0; therefore, DU = Q – W = 0, or Q = W
d.	DV = 0, so PDV = 0 and W = 0; therefore, DU = Q

16. The first law of thermodynamics is actually a restatement of

a.	Newton's first law.	c.	the law of conservation of momentum.
b.	the law of universal gravitation.	d.	the law of conservation of energy.

17. Which law of thermodynamics tells is that whenever work is done the net change in entropy is always positive?

a.	The 0^th law	c.	The 2^nd law
b.	The 1^st law	d.	The 3^rd law

18. In an adiabatic process

a.	energy as heat is not exchanged.	c.	energy as heat is quickly exchanged.
b.	energy as heat is slowly exchanged.	d.	energy as heat is completely removed.

19. In order for energy to be exchanged between two systems

a.	the process must be adiabatic.	c.	the systems must be in thermal equilibrium.
b.	the process must be isothermal.	d.	the systems must not be in thermal equilibrium.

20. By definition a cyclic system

a.	never returns to its initial condition.	c.	always returns to its initial condition but with a tiny bit of ' lost' energy.
b.	always returns to its initial condition.	d.	always returns to its initial condition but with a tiny bit of 'extra' energy.

21. Whenever the internal energy of a system cahnges you know that

a.	work was done on or by the system.	c.	the volume of the system also cahnged.
b.	the system is isolated.	d.	the temperature of the system also changed.

22. Every engine, including the human body, is a heat engine. Every heat engine has a hot place and a cold place between which work is done. This means that every heat engine

a.	works best when the hot and cold place are closest in temperature.	c.	works best when there is no difference in the temperature between the hot and cold place.
b.	works best when the hot and cold place are fartherest apart in temperature.	d.	works best when there is no hot or cold place.

23. Blowing up a balloon is an

a.	isothermal thermodynamic process.	c.	isobaric thermodynamic process.
b.	isovolumetric thermodynamic process.	d.	adiabatic thermodynamic process.

24. If a system has a high potential for change its entropy must be

a.	high.	c.	nonexistent.
b.	low	d.	unchangable

25. When water condenses its entropy

a.	decreases.	c.	remains unchanged.
b.	increases.	d.	falls to aero.

Short Answer (90)

Answer the questions below in complete sentences on your own paper. Answer each question on its own page. Answer all questions in a vertically aligned 'a', 'b', 'c' format. You will receive ten points for each part of each question.

26. Consider a salt solution set in the sun.

a) State the second law of thermodynamics in terms of entropy.

Answer the following questions:

b) Does the dissolved salt have more or less entropy than salt crystals? What happens to the entropy of the salt as the water evaporates?

c) Does the liquid water have more or less entropy than the evaporated water? What happens to the entropy of the water as it evaporates?

d) As the water evaporates the salt crystallizes; explain how this does not violate the second law of thermodynamics, as stated above.

27. Consider the first two laws of thermodynamics.

a) State the first law of thermodynamics in terms of energy conservation

b) Write the equation for the first law in symbols and in english

c) State the second law of thermodynamics in terms of energy transformations

d) Explain why the first and second law do not contradict each other.

e) Rewrite the first law equation so that it takes into consideration your explaination.

PAPP Chapter 11: Thermodynamics

Answer Section

MULTIPLE CHOICE

1. A

2. B

3. D

4. A

5. B

6. C

7. B

8. D

9. D

10. D

11. A

12. B

13. A

14. B

15. B

16. D

17. C

18. A

19. D

20. B

21. A

22. B

23. D

24. B

25. A

SHORT ANSWER

26. Considering a salt solution set in the sun.

a) The second law of thermodynamics in terms of entropy states that for all natural preocesses entropy always increases. According to the second law of thermodynamics, stated in this way:

b) Dissolved salt has more entropy than crystallized salt. So, as the salt crystallizes the entropy of the salt decreases.

c) Liquid water has less entropy than water vapor. So, as the water vaporizes the entropy of the water increases.

d) As the water vaporizes the salt crystallizes. This process does not violate the second law of thermodynamics as stated above because the change in entropy of the salt is less than the change in entropy of the water. In other words, the vaporized water has more entropy than the dissolved salt. Therefore the net change in entropy for the vaproizing water-crystalizing salt process is positive.

27. a) The first law of thermodynamics in terms of consrvation of energy states that energy is always conserved, or energy cannot be created nor destroyed.

b) The equation for the first law is DU = Q - W. The change in the internal energy of a system is equal to the sum of the energy as heat that enters or leaves the system and the work done on or by the system.

c)The second law of thermodynamics in terms of energy transformation states that whenever energy is transferred from one kind to another or from one place to another some energy is always lost, or 'gets away’.

d) The first law contradicts the second law only if you do not take into consideration the energy that "got away". Without this energy that 'got away' it seems that you are always left with less energy than you started with. This is, of course, a violation of the first law.

The first law is not contradicted by the second law if you take into account all of the energy that was transferred from one kind to another or from one place to another along with the energy that "got away". By doing this all of the energy you stated with would equal all the energy you ended up with.

e) One might re-write the first law equation to reflect this: DU = (Q - W) + Q