Questions on Entropy
Multiple-Choice Questions: Entropy
1. What does entropy measure in a thermodynamic system?
A) Energy lost as heat
B) The total internal energy
C) The amount of disorder or randomness
D) The capacity to do work
E) The number of particles
2. Which of the following has the highest entropy at standard conditions?
A) Ice
B) Liquid water
C) Steam (water vapor)
D) Sodium chloride crystal
E) A diamond
3. As a system becomes more disordered, entropy:
A) Decreases
B) Remains constant
C) Increases
D) Becomes negative
E) Approaches zero
4. Which process involves an increase in entropy?
A) Freezing of water
B) Condensation of vapor
C) Sublimation of dry ice
D) Formation of salt from its ions
E) Deposition of frost
5. The second law of thermodynamics states that:
A) All reactions are spontaneous
B) The total energy of a system is conserved
C) Entropy always decreases in a closed system
D) Entropy of the universe tends to increase
E) Entropy remains constant during reactions
6. Which has the greatest standard molar entropy (S°)?
A) O₂ (g)
B) H₂O (l)
C) NaCl (s)
D) CO₂ (g)
E) H₂O (s)
7. In which of the following processes does entropy decrease?
A) Boiling water
B) Melting ice
C) Condensing steam
D) Dissolving salt in water
E) Vaporizing alcohol
8. Entropy is measured in:
A) Joules (J)
B) Calories (cal)
C) Joules per mole (J/mol)
D) Joules per Kelvin (J/K)
E) Kilojoules per mole (kJ/mol)
9. Which of the following reactions has a positive entropy change (ΔS > 0)?
A) 2H₂(g) + O₂(g) → 2H₂O(l)
B) H₂O(l) → H₂O(s)
C) N₂(g) + 3H₂(g) → 2NH₃(g)
D) CaCO₃(s) → CaO(s) + CO₂(g)
E) 2SO₂(g) + O₂(g) → 2SO₃(g)
10. Which of the following contributes most to a high entropy value?
A) Orderly crystal structure
B) Low molecular motion
C) A large number of microstates
D) Fewer possible configurations
E) A single stable phase
11. What is true of entropy at absolute zero (0 K)?
A) It is infinite
B) It is undefined
C) It is zero for a perfect crystal
D) It is maximal
E) It is negative
12. An increase in the number of gas particles typically results in:
A) A decrease in entropy
B) No change in entropy
C) An increase in entropy
D) Entropy becoming zero
E) Condensation
13. Which of the following systems has the lowest entropy?
A) A gas at high pressure
B) A solid at 0 °C
C) A saturated salt solution
D) A gas at low pressure
E) A liquid evaporating
14. In chemical reactions, a positive entropy change usually means:
A) The reaction is exothermic
B) The products are more disordered than reactants
C) Energy is absorbed
D) Temperature is decreased
E) The system has lower energy
15. Which phase change shows the greatest increase in entropy?
A) Freezing
B) Melting
C) Condensation
D) Sublimation
E) Deposition
16. In terms of entropy, the mixing of two gases results in:
A) Lower entropy due to collisions
B) No change in entropy
C) Greater entropy due to more microstates
D) A decrease in enthalpy
E) Formation of new bonds
17. The entropy of a system tends to increase when:
A) Solids form from liquids
B) Gases dissolve into liquids
C) Liquids freeze
D) Solids dissolve into liquids
E) Gases condense
18. Which thermodynamic quantity includes entropy as a component?
A) Enthalpy (H)
B) Internal energy (U)
C) Work (w)
D) Gibbs free energy (G)
E) Heat capacity (C)
19. Which statement is true about entropy in spontaneous reactions?
A) Entropy must always increase in the system
B) The total entropy change of system and surroundings must be positive
C) Entropy has no role in spontaneity
D) The entropy of surroundings must be zero
E) Entropy only increases in endothermic reactions
20. Entropy is associated with:
A) Mass
B) Heat energy
C) Randomness and number of configurations
D) Pressure
E) Activation energy
- Questions on Effect of Concentration, Temperature, and Pressure
- Questions on Solubility Product Constant (Ksp)
- Questions on Common Ion Effect
Answer Key with Explanations
1. C – Entropy is the measure of disorder or randomness in a system.
2. C – Gases have higher entropy than liquids or solids; steam is gaseous.
3. C – Entropy increases as disorder increases.
4. C – Sublimation increases disorder dramatically as solid becomes gas.
5. D – The second law says total entropy of the universe tends to increase.
6. D – CO₂ (g) is a gas with many microstates, thus highest entropy.
7. C – Condensation forms a liquid from a gas, reducing entropy.
8. D – Entropy is measured in J/K (Joules per Kelvin).
9. D – A solid breaking down into a solid and gas increases entropy.
10. C – A large number of microstates (configurations) increases entropy.
11. C – At 0 K, a perfect crystal has zero entropy (third law of thermodynamics).
12. C – More gas particles → more disorder → increased entropy.
13. B – Solids at low temperatures have the lowest entropy.
14. B – More disordered products mean a positive ΔS.
15. D – Sublimation (solid to gas) increases entropy the most.
16. C – Mixing gases increases possible microstates, raising entropy.
17. D – Solids dissolving increase particle movement and disorder.
18. D – Gibbs free energy (G = H - TΔS) includes entropy.
19. B – For spontaneity, total entropy of system and surroundings must increase.
20. C – Entropy relates to randomness and number of possible arrangements.
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