Second law of thermodynamics, reversible and irreversible processes - Question Bank

1. The efficiency of any real heat engine (irreversible) operating between two temperatures is always:
A) Equal to the Carnot efficiency.
B) Greater than the Carnot efficiency.
C) Less than the Carnot efficiency.
D) Zero.
2. A perfectly reversible process requires:
A) Rapid changes in state.
B) No heat transfer.
C) The system to be in equilibrium with its surroundings at all times.
D) Significant friction.
3. The second law of thermodynamics is fundamentally about the:
A) Conservation of energy
B) Direction of natural processes
C) Absolute temperature scale
D) Equilibrium states
4. Which of the following is a characteristic of an irreversible process?
A) The process can be reversed by an infinitesimal change.
B) The system is always in thermodynamic equilibrium.
C) There is always a dissipation of energy.
D) The total entropy of the universe remains constant.
5. The entropy of a system can decrease if:
A) It is an isolated system and the process is spontaneous.
B) It exchanges heat with the surroundings, and the entropy increase of the surroundings is greater than the entropy decrease of the system.
C) It undergoes a reversible adiabatic process.
D) It is a perfect gas undergoing isothermal expansion.
6. When a gas expands against a vacuum, the process is:
A) Reversible and entropy increases.
B) Irreversible and entropy increases.
C) Reversible and entropy remains constant.
D) Irreversible and entropy remains constant.
7. The concept of 'available energy' or 'useful work' is limited by:
A) The first law of thermodynamics
B) The second law of thermodynamics
C) The third law of thermodynamics
D) The law of conservation of momentum
8. An irreversible process can be characterized by:
A) A net increase in entropy of the universe.
B) The ability to return to the initial state without external work.
C) A constant entropy change for the system and surroundings.
D) The absence of any heat transfer.
9. The statement 'heat cannot spontaneously flow from a colder body to a hotter body' is attributed to:
A) Kelvin
B) Planck
C) Clausius
D) Carnot
10. Which condition is essential for a process to be reversible?
A) It must be adiabatic.
B) The system must be far from equilibrium.
C) The process must occur infinitely slowly.
D) There must be no heat transfer.
11. If a system undergoes a reversible isothermal expansion, then:
A) Heat flows out of the system.
B) The internal energy of the system increases.
C) Work is done by the system.
D) The entropy of the system decreases.
12. The tendency for systems to move towards a state of greater disorder is a direct consequence of:
A) The first law of thermodynamics
B) The second law of thermodynamics
C) Newton's laws of motion
D) The law of conservation of mass
13. Which statement is true regarding irreversible processes?
A) They can be reversed without any change in the surroundings.
B) They are always very slow.
C) They always lead to an increase in the total entropy of the universe.
D) They do not dissipate energy.
14. For any process occurring in an isolated system, the total entropy change is:
A) Always zero
B) Always positive
C) Always negative
D) Zero or positive
15. The maximum efficiency of a heat engine is achieved when it operates on a:
A) Irreversible cycle
B) Carnot cycle
C) Brayton cycle
D) Rankine cycle
16. A process that occurs spontaneously in nature is always:
A) Reversible
B) Irreversible
C) Adiabatic
D) Isothermal
17. The second law of thermodynamics implies that it is impossible to:
A) Convert all heat into work in a single process.
B) Decrease the entropy of an isolated system.
C) Achieve absolute zero temperature.
D) All of the above.
18. If a system absorbs heat Q reversibly at temperature T, the change in its entropy is:
A) Q/T
B) -Q/T
C) T/Q
D) 0
19. Which of the following processes is best approximated as a reversible process in many thermodynamic analyses?
A) Explosion of a bomb
B) Sudden compression of a gas
C) Slow evaporation of a liquid
D) Burning of fuel
20. The concept of entropy increase is fundamentally linked to:
A) The conservation of energy
B) The directionality of time
C) The stability of matter
D) The expansion of the universe
21. For an irreversible process in an isolated system, the change in entropy (ΔS) satisfies:
A) ΔS < 0
B) ΔS = 0
C) ΔS > 0
D) ΔS ≤ 0
22. A refrigerator's operation is based on which principle?
A) First law of thermodynamics
B) Second law of thermodynamics (Clausius statement)
C) Second law of thermodynamics (Kelvin-Planck statement)
D) Third law of thermodynamics
23. Which of the following is a necessary condition for a process to be reversible?
A) It must be adiabatic.
B) The temperature difference between the system and surroundings must be zero.
C) It must be spontaneous.
D) It must occur very rapidly.
24. The process of rusting of iron is an example of:
A) A reversible process
B) An irreversible process
C) A process that decreases entropy
D) An isothermal process
25. If a process is irreversible, then the change in entropy of the system plus the change in entropy of the surroundings is:
A) Equal to zero
B) Less than zero
C) Greater than zero
D) Equal to the work done
26. Consider a heat engine operating between 500 K and 300 K. If the engine is reversible, its maximum possible efficiency is:
A) 0.4
B) 0.5
C) 0.6
D) 0.8
27. The second law of thermodynamics is often referred to as the law of:
A) Conservation of energy
B) Conservation of mass
C) Increasing entropy
D) Conservation of momentum
28. Which of the following is NOT a characteristic of a reversible process?
A) Occurs infinitesimally slowly.
B) System is always in equilibrium with surroundings.
C) Involves dissipative forces like friction.
D) Can be reversed without leaving any trace on the surroundings.
29. For a system undergoing a reversible adiabatic process, the change in entropy is:
A) Positive
B) Negative
C) Zero
D) Cannot be determined
30. Which phenomenon demonstrates the irreversibility of natural processes?
A) A pendulum swinging indefinitely without friction.
B) A perfectly elastic collision between two objects.
C) The mixing of two different gases at room temperature.
D) The melting of ice at its melting point.
31. In any irreversible process, the net change in entropy of the universe is:
A) Zero
B) Negative
C) Positive
D) Indeterminate
32. The second law of thermodynamics places a fundamental limit on:
A) The total amount of energy that can be created.
B) The efficiency of converting heat into work.
C) The rate at which processes can occur.
D) The conservation of mass.
33. Heat transfer due to a finite temperature difference is:
A) A reversible process
B) An irreversible process
C) An isothermal process
D) An adiabatic process
34. A process that involves rapid changes in pressure and temperature, leading to non-equilibrium states, is typically:
A) Reversible
B) Isothermal
C) Irreversible
D) Adiabatic and reversible
35. Which of the following is a consequence of the second law of thermodynamics?
A) Energy is always conserved.
B) The direction of spontaneous processes is towards increasing entropy.
C) Absolute zero temperature is unattainable.
D) Both B and C.
36. The efficiency of a reversible heat engine operating between temperatures T1 (hot) and T2 (cold) is given by:
A) 1 - T1/T2
B) 1 - T2/T1
C) T1/(T1 - T2)
D) T2/(T1 - T2)
37. The Carnot cycle is an example of a cycle that operates between two heat reservoirs. It is:
A) An irreversible cycle
B) A reversible cycle
C) A cycle that can be performed in reality
D) A cycle with 100% efficiency
38. Consider the free expansion of an ideal gas into a vacuum. Which of the following is true for this irreversible process?
A) ΔU = 0, ΔS > 0
B) ΔU > 0, ΔS = 0
C) ΔU = 0, ΔS = 0
D) ΔU < 0, ΔS > 0
39. A gas expands isothermally and reversibly. In this process:
A) Heat is absorbed by the gas.
B) Work is done by the gas.
C) The internal energy of the gas remains constant.
D) All of the above.
40. Which statement about entropy is correct?
A) Entropy is a measure of the order in a system.
B) Entropy is a measure of the randomness or disorder in a system.
C) Entropy can only increase in an isolated system.
D) Entropy is always a positive quantity.
41. The entropy of the universe tends to:
A) Decrease in all spontaneous processes.
B) Remain constant in all processes.
C) Increase in all spontaneous processes.
D) Decrease only in reversible processes.
42. Which of the following conditions must be met for a process to be considered reversible?
A) It must occur rapidly.
B) It must involve significant friction.
C) It must be carried out infinitely slowly, with the system always in equilibrium with its surroundings.
D) It must be adiabatic.
43. The change in entropy (ΔS) for a reversible process is defined as:
A) ΔS = Q/T
B) ΔS = -Q/T
C) ΔS = W/T
D) ΔS = -W/T
44. In a reversible process, the work done by the system is:
A) Always greater than the work done in an irreversible process between the same states.
B) Always less than the work done in an irreversible process between the same states.
C) Equal to the work done in an irreversible process between the same states.
D) Not comparable to the work done in an irreversible process.
45. Which type of process involves significant dissipation of energy, making it impossible to reverse without leaving a permanent change in the surroundings?
A) Reversible process
B) Quasistatic process
C) Irreversible process
D) Isentropic process
46. The Kelvin-Planck statement of the second law of thermodynamics is related to:
A) The impossibility of perpetual motion machines of the first kind.
B) The impossibility of perpetual motion machines of the second kind.
C) The increase in entropy in spontaneous processes.
D) The definition of absolute temperature.
47. The Clausius statement of the second law of thermodynamics states that:
A) It is impossible to construct a device which operates in a cycle and produces no effect other than the extraction of heat from a single reservoir and the performance of an equivalent amount of work.
B) It is impossible to transfer heat from a colder body to a hotter body without the aid of an external agent.
C) The entropy of an isolated system never decreases.
D) The efficiency of a heat engine is always less than 1.
48. Which of the following is an example of an irreversible process?
A) Slow compression of a gas in an insulated cylinder
B) Melting of ice at 0°C and 1 atm pressure
C) Free expansion of a gas into a vacuum
D) Diffusion of a gas into another gas
49. A process that can be reversed by an infinitesimal change in conditions, restoring both the system and surroundings to their initial states, is called:
A) Irreversible process
B) Isothermal process
C) Adiabatic process
D) Reversible process
50. Which of the following statements best describes the second law of thermodynamics?
A) The total energy of an isolated system is conserved.
B) In any spontaneous process, the total entropy of the universe increases.
C) The entropy of a perfect crystal at absolute zero is zero.
D) Heat cannot spontaneously flow from a colder body to a hotter body.
All Question Banks
E-Book Second law of thermodynamics, reversible and irreversible processes One Line Questions Second law of thermodynamics, reversible and irreversible processes Online Test Second law of thermodynamics, reversible and irreversible processes