31. The Third Law of Thermodynamics implies that:

• A) The entropy of a perfect crystal approaches zero as temperature approaches absolute zero
• B) Entropy can be negative
• C) All substances have the same entropy at absolute zero
• D) Temperature can never reach absolute zero
• Answer: A

32. Which of the following scenarios describes an increase in entropy?

• A) A gas condensing into a liquid
• B) Water freezing into ice
• C) A solid dissolving in a solvent
• D) A system reaching thermal equilibrium
• Answer: C

33. In thermodynamics, which of the following best describes a reversible reaction?

• A) It releases heat
• B) It occurs at constant temperature
• C) It can return to its original state without net changes in the universe
• D) It is always exothermic
• Answer: C

34. For a process at constant temperature and pressure, the change in Gibbs free energy is directly related to:

• A) Enthalpy and entropy changes
• B) Heat capacity
• C) Work done by the system
• D) Volume changes
• Answer: A

35. The Second Law of Thermodynamics is often illustrated using:

• A) The Carnot cycle
• B) The Dalton theory
• C) The ideal gas law
• D) The kinetic theory of gases
• Answer: A

36. If the entropy of the universe is decreasing, it implies:

• A) The process is spontaneous
• B) The process is non-spontaneous
• C) The system is at equilibrium
• D) The system has reached absolute zero
• Answer: B

37. In a cyclic process, the change in internal energy is:

• A) Positive
• B) Negative
• C) Zero
• D) Dependent on heat transfer
• Answer: C

38. Which of the following statements is true regarding an irreversible process?

• A) It can be reversed by an infinitesimal change
• B) It does not change the total entropy
• C) It increases the total entropy of the universe
• D) It is always accompanied by a decrease in energy
• Answer: C

39. The entropy of an ideal gas depends on:

• A) Volume and pressure only
• B) Temperature and volume
• C) Temperature and pressure only
• D) All of the above
• Answer: D

40. The efficiency of a heat engine operating between two heat reservoirs is given by:

• A) 1 – (T_C/T_H)
• B) T_C/T_H
• C) 1 – (T_H/T_C)
• D) T_H/T_C
• Answer: A