R1.4 Entropy and spontaneity Quiz
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5 questions, one answer each
Each answer is checked as you go, with why.
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1. Which process has a positive ΔS?
- A. H₂O(g) → H₂O(l)
- B. N₂(g) + 3H₂(g) → 2NH₃(g)
- C. CaCO₃(s) → CaO(s) + CO₂(g)
- D. Ag⁺(aq) + Cl⁻(aq) → AgCl(s)
2. ΔH = −50 kJ mol⁻¹ and ΔS = −100 J K⁻¹ mol⁻¹. Above what temperature is the reaction non-spontaneous?
- A. 50 K
- B. 200 K
- C. 500 K
- D. 5000 K
3. ΔG⦵ for a reaction is −10 kJ mol⁻¹ at 298 K. What can be said about K?
- A. K = 0
- B. K < 1
- C. K = 1
- D. K > 1
4. At equilibrium, what is the value of ΔG?
- A. Zero
- B. ΔG⦵
- C. −RT
- D. Negative
5. Why must ΔS be divided by 1000 in ΔG = ΔH − TΔS?
- A. To convert K to °C
- B. ΔS is in J K⁻¹ mol⁻¹ but ΔH is in kJ mol⁻¹
- C. Because T is large
- D. To convert per mole to per molecule