2nd and 3rd Law of Thermodynamics and Entropy MCQs

41. Which of the following increases the entropy of a system?

• A) Compressing a gas
• B) Freezing water
• C) Melting ice
• D) Decreasing temperature
• Answer: C

42. The total entropy of a system and its surroundings in a spontaneous process:

• A) Remains constant
• B) Decreases
• C) Increases
• D) Is zero
• Answer: C

43. The entropy change during a phase transition at constant temperature is:

• A) Zero
• B) Positive
• C) Negative
• D) Depends on the phase change
• Answer: B

44. In a heat pump, the work done is used to:

• A) Increase the heat removed from the cold reservoir
• B) Transfer heat from a cold to a hot reservoir
• C) Convert work into heat
• D) Decrease the temperature of the hot reservoir
• Answer: B

45. In a reversible isothermal process, the change in internal energy of an ideal gas is:

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

46. The entropy of a gas increases when:

• A) The gas is compressed
• B) The temperature decreases
• C) The volume increases
• D) The pressure increases
• Answer: C

47. What is the standard entropy change for a reaction?

• A) The difference between the entropies of products and reactants at standard conditions
• B) The heat absorbed at constant temperature
• C) The change in enthalpy
• D) The work done during the reaction
• Answer: A

48. Which of the following reactions would likely have a positive change in entropy?

• A) Formation of ice from water
• B) Combustion of hydrocarbons
• C) Synthesis of ammonia
• D) Decomposition of hydrogen peroxide
• Answer: D

49. The term ‘Gibbs free energy’ is often associated with:

• A) Maximum work obtainable from a process
• B) Minimum energy required to start a reaction
• C) Total energy of a system
• D) Heat absorbed at constant volume
• Answer: A

50. If a process is both isothermal and reversible, the change in Gibbs free energy is:

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