Entropy and spontaneity Quiz
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5 questions, one answer each
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1. Which has the highest standard entropy at 298 K?
- A. 1 mol of steam
- B. 1 mol of ice
- C. 1 mol of liquid water
- D. 1 mol of an ionic solid
2. A reaction has ΔH = −50 kJ mol⁻¹ at 300 K. What is ΔS surroundings?
- A. −167 J K⁻¹ mol⁻¹
- B. +167 J K⁻¹ mol⁻¹
- C. +0.167 J K⁻¹ mol⁻¹
- D. +15 000 J K⁻¹ mol⁻¹
3. For which reaction is ΔS system most clearly positive?
- A. 2Mg(s) + O₂(g) → 2MgO(s)
- B. N₂(g) + 3H₂(g) → 2NH₃(g)
- C. 2H₂(g) + O₂(g) → 2H₂O(l)
- D. CaCO₃(s) → CaO(s) + CO₂(g)
4. ΔS system = +120 J K⁻¹ mol⁻¹ and ΔS surroundings = −90 J K⁻¹ mol⁻¹. What is true?
- A. The reaction is not feasible
- B. ΔS total = +30 J K⁻¹ mol⁻¹ and the reaction is feasible
- C. ΔS total = +210 J K⁻¹ mol⁻¹
- D. ΔS total = −30 J K⁻¹ mol⁻¹
5. Why does ΔS surroundings = −ΔH/T become less positive for an exothermic reaction at higher temperatures?
- A. ΔH becomes smaller
- B. The system loses more entropy
- C. The same energy is shared among surroundings at a higher temperature, so a smaller entropy increase
- D. The reaction becomes endothermic