Unit 7: Thermochemistry

41. What is the effect of temperature on the entropy of a system?

a) Increases with temperature
b) Decreases with temperature
c) Remains constant
d) Changes unpredictably
Answer: a) Increases with temperature

42. Which of the following reactions is likely to have a positive entropy change?

a) Freezing of water
b) Dissolving of salt in water
c) Condensation of steam
d) Formation of ice
Answer: b) Dissolving of salt in water

43. In an endothermic reaction, the enthalpy change is:

a) Positive
b) Negative
c) Zero
d) Undefined
Answer: a) Positive

44. The entropy of a perfect crystalline substance at absolute zero is:

a) Zero
b) Positive
c) Negative
d) Undefined
Answer: a) Zero

45. The heat change in a reaction is related to which of the following?

a) Kinetics
b) Equilibrium
c) Thermodynamics
d) Stoichiometry
Answer: c) Thermodynamics

46. Which of the following is true for a spontaneous reaction at constant temperature and pressure?

a) ΔG > 0
b) ΔG < 0
c) ΔG = 0
d) ΔG is undefined
Answer: b) ΔG < 0

47. What is the relationship between free energy change (ΔG) and spontaneity of a reaction?

a) ΔG > 0 indicates a spontaneous reaction
b) ΔG < 0 indicates a non-spontaneous reaction
c) ΔG = 0 indicates equilibrium
d) ΔG > 0 indicates equilibrium
Answer: c) ΔG = 0 indicates equilibrium

48. Which of the following statements is true regarding exothermic reactions?

a) They absorb heat from the surroundings
b) They release heat to the surroundings
c) They have a positive ΔH
d) They do not involve heat exchange
Answer: b) They release heat to the surroundings

49. Which of the following is NOT a state function?

a) Enthalpy
b) Entropy
c) Work
d) Internal energy
Answer: c) Work

50. What is the term used to describe the amount of energy available to do work in a system?

a) Internal energy
b) Free energy
c) Enthalpy
d) Entropy
Answer: b) Free energy