Feasibility of redox reactions Quiz
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5 questions, one answer each
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1. Which reaction is feasible? E°: Zn²⁺|Zn −0.76 V, Cu²⁺|Cu +0.34 V, Ag⁺|Ag +0.80 V, Fe³⁺|Fe²⁺ +0.77 V.
- A. Zn(s) + Cu²⁺(aq) → Zn²⁺(aq) + Cu(s)
- B. Cu(s) + Zn²⁺(aq) → Cu²⁺(aq) + Zn(s)
- C. Ag(s) + Fe³⁺(aq) → Ag⁺(aq) + Fe²⁺(aq)
- D. Cu(s) + 2H⁺(aq) → Cu²⁺(aq) + H₂(g)
2. What is disproportionation?
- A. Two different species swap electrons
- B. The same species is both oxidised and reduced
- C. A species is only reduced
- D. A reaction that is too slow to observe
3. A reaction has E°cell = −0.40 V at 298 K. What can be deduced?
- A. ΔS_total is positive and K is greater than 1
- B. The reaction is fast but incomplete
- C. ΔS_total is negative and K is less than 1
- D. The reaction has no activation energy
4. Why might a reaction with a positive E°cell not be observed?
- A. The equilibrium constant must be less than 1
- B. E°cell is always negative for slow reactions
- C. The electrons cannot pass through the salt bridge
- D. It may have a high activation energy, so it is too slow
5. MnO₂ reacts with concentrated HCl to make Cl₂ although E°cell = −0.13 V. Why?
- A. The concentrations are not standard, so the electrode potentials shift
- B. E° values are only correct for solids
- C. Hydrochloric acid changes the value of E° for chlorine permanently
- D. The reaction has a negative activation energy