Total entropy change and feasibility Quiz
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5 questions, one answer each
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1. A reaction has ΔH = −120 kJ mol⁻¹ and ΔSsystem = −150 J K⁻¹ mol⁻¹. What is ΔStotal at 300 K?
- A. −550 J K⁻¹ mol⁻¹
- B. +250 J K⁻¹ mol⁻¹
- C. −0.55 J K⁻¹ mol⁻¹
- D. +550 J K⁻¹ mol⁻¹
2. Which statement about an endothermic reaction that happens spontaneously at room temperature is correct?
- A. ΔSsurroundings must be positive
- B. ΔSsystem must be negative
- C. ΔSsystem is positive and outweighs the negative ΔSsurroundings
- D. ΔH must be zero
3. For a reaction with ΔH = +60 kJ mol⁻¹ and ΔSsystem = +200 J K⁻¹ mol⁻¹, what is the minimum feasible temperature?
- A. 0.30 K
- B. 120 K
- C. 12 000 K
- D. 300 K
4. Why does raising the temperature make an endothermic reaction more likely to be feasible?
- A. ΔH becomes less positive
- B. The activation energy falls
- C. The negative ΔSsurroundings (−ΔH/T) becomes smaller in magnitude
- D. ΔSsystem becomes negative
5. Hydrogen and oxygen can be mixed at room temperature with no reaction, though ΔStotal for forming water is strongly positive. This is because the mixture is
- A. thermodynamically stable and kinetically unstable
- B. thermodynamically unstable and kinetically stable
- C. both thermodynamically and kinetically stable
- D. not feasible