Entropy topics include: Entropy property, temperature entropy, entropy applications and mechanisms, entropy generations, first and second laws, reversible adiabatic work. In thermodynamics, entropy is a quantitative measure of the disorder or randomness in a system. It's also known as a thermodynamic function, which is a thermodynamic quantity whose change is independent of the system's path.  Entropy is central to the second law of thermodynamics, which states that the entropy of an isolated system cannot decrease with time. This means that isolated systems evolve toward thermodynamic... Show more

Entropy topics include: Entropy property, temperature entropy, entropy applications and mechanisms, entropy generations, first and second laws, reversible adiabatic work.

In thermodynamics, entropy is a quantitative measure of the disorder or randomness in a system. It's also known as a thermodynamic function, which is a thermodynamic quantity whose change is independent of the system's path. 

Entropy is central to the second law of thermodynamics, which states that the entropy of an isolated system cannot decrease with time. This means that isolated systems evolve toward thermodynamic equilibrium, where the entropy is highest. 
Entropy is also a measure of the number of microscopic ways a system can be arranged to give the same macroscopic thermodynamic state. The second law of thermodynamics uses entropy to assess the spontaneity of a process. 
Entropy is a scientific concept that is used in many fields, including: Classical thermodynamics, Statistical physics, Information theory, Chemistry and physics, Biological systems, Cosmology, Economics, Sociology, Weather science, Climate change, Information systems. 

Related Test: Thermodynamics Practice Test: Second Law of Thermodynamics

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Thermodynamics Practice Test: Entropy

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25 Questions

1. Entropy increase dS of the system can be expressed as

dS=dS(due to external heat interaction)+dS(due to internal irreversibility)dS=-dS(due to external heat interaction)+dS(due to internal irreversibility)dS=dS(due to external heat interaction)-dS(due to internal irreversibility)dS=-dS(due to external heat interaction)-dS(due to internal irreversibility)

2. Any thermodynamic process is accompanied by entropy generation.

TrueDon't KnowFalseMaybe

3. The equation TdS=dU+pdV is obtained from which law?

none of thesefirst lawboth of the mentionedsecond law

4. Entropy may decrease locally at some region within the isolated system. How can this statement be justified?

none of thesethis cannot be possibleit must be compensated by a greater increase of entropy somewhere within the system.this is possible because entropy of an isolated system can decrease.

5. A chip dissipates 2 kJ of electric work and rejects it as heat transfer from its surface which is at 50°C to 25°C air. How much entropy is generated in the chip?

7.19 J/K4.19 J/K6.19 J/K5.19 J/K

6. The first law of thermodynamics makes no distinction between heat transfer and work.

MaybeFalseDon't KnowTrue

7. For the flow of electric current through a resistor,

all of the mentionedat steady state, temperature of resistor is constantat steady state, internal energy of resistor is constantW=Q

8. In an open system, there is a transfer of which of the following quantity?

entropyall of the mentionedenergymass

9. If the path A causes more entropy generation than path B, then

none of thesepath A is more irreversible than path Bboth of the mentionedpath A involves more lost work

10. A foundry form box with 25 kg of 200°C hot sand is dropped into a bucket with 50 L water at 15°C. Assuming there is no heat transfer with the surroundings and no boiling away of water, calculate the net entropy change for the process.

2.37 kJ/K2.57 kJ/K2.47 kJ/K2.67 kJ/K

11. The entropy increase due to internal irreversibility is also called entropy production or entropy generation.

TrueMaybeFalseDon't Know

12. A process always occurs in such a direction as to cause an increase in the entropy of the universe.

TrueMaybeFalseDon't Know

13. Entropy transfer for an adiabatic transfer is zero.

MaybeFalseTrueDon't Know

14. The entropy of an isolated system can never ____

decreasenone of theseincreasebe zero

15. In a Carnot engine working on ammonia, the high temperature is 60°C and as QH is received, the ammonia changes from saturated liquid to saturated vapor. The ammonia pressure at low temperature is 190 kPa. Find the entropy.

7.6577 kJ/kg K5.6577 kJ/kg K4.6577 kJ/kg K6.6577 kJ/kg K

16. A hot metal piece is cooled rapidly to 25°C, removing 1000 kJ from the metal. Calculate the change of entropy if energy is absorbed by vaporizing liquid nitrogen at 101.3 kPa pressure.

11.929 kJ/K12.929 kJ/K9.929 kJ/K10.929 kJ/K

17. For a reversible heat transfer and process being adiabatic, which of the following is true?

dS=0all of the mentioneddQ=0S=constant

18. Mass contains

none of theseboth of the mentionedenergyentropy

19. Argon in a light bulb is at 90 kPa and heated from 20°C to 60°C with electrical power. Find the total entropy generation per unit mass of argon.

0.03 kJ/kg K0.04 kJ/kg K0.02 kJ/kg K0.05 kJ/kg K

20. A pan contains 5 L of engine oil at 20°C, 100 kPa. Now 2 L of hot 100°C oil is mixed into the pan. Find the entropy generation.

0.1028 kJ/K0.0928 kJ/K0.0728 kJ/K0.0828 kJ/K

21. When work is dissipated into internal energy, what is the change in the disorderly motion of molecules.

decreasesnone of theseincreasesremains same

22. Which of the following processes exhibit external mechanical irreversibility?

none of theseisothermal dissipation of workboth of the mentionedadiabatic dissipation of work

23. The equation TdS=dU+pdV holds good for

reversible processnone of theseboth of the mentioned

24. Entropy can be transferred to or from a system in which of the following forms?

mass flowheat transfernone of theseboth of the mentioned

25. Which of the following is true?

the PE is due to the displacement of molecules from their normal positionsall of the mentionedthe KE of a gas is due to the coordinated motion of of all the molecules with same average velocity in same directionheat energy is due to the random thermal motion of molecules in a disorderly fashion