Electrochemical Series
Consider the following standard reduction potentials: E°(Ag⁺/Ag) = +0.80 V, E°(Cu²⁺/Cu) = +0.34 V, E°(Zn²⁺/Zn) = −0.76 V, E°(Fe²⁺/Fe) = −0.44 V. Which metal can reduce Cu²⁺ ions but cannot reduce Ag⁺ ions from their aqueous solutions?
Select the correct option:
Solution
None of the above — any metal that reduces Cu²⁺ will also reduce Ag⁺
A metal can reduce a cation if the metal has a lower (more negative) standard reduction potential than the cation. Since E°(Ag⁺/Ag) = +0.80 V is higher than E°(Cu²⁺/Cu) = +0.34 V, any metal capable of reducing Cu²⁺ (i.e., having E° < +0.34 V) will automatically also have E° < +0.80 V, meaning it can also reduce Ag⁺. In the electrochemical series, Ag⁺ is a stronger oxidising agent than Cu²⁺. Therefore, no metal exists that reduces Cu²⁺ but fails to reduce Ag⁺. This question tests deep conceptual understanding of the relative positions in the electrochemical series and the transitive nature of reduction potential comparisons.
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About This Question
- Subject
- chemistry
- Chapter
- redox reactions and electrochemistry
- Topic
- electrochemical series
- Difficulty
- Hard
- Year
- 2025
Solution
Correct Answer:
None of the above — any metal that reduces Cu²⁺ will also reduce Ag⁺
A metal can reduce a cation if the metal has a lower (more negative) standard reduction potential than the cation. Since E°(Ag⁺/Ag) = +0.80 V is higher than E°(Cu²⁺/Cu) = +0.34 V, any metal capable of reducing Cu²⁺ (i.e., having E° < +0.34 V) will automatically also have E° < +0.80 V, meaning it can also reduce Ag⁺. In the electrochemical series, Ag⁺ is a stronger oxidising agent than Cu²⁺. Therefore, no metal exists that reduces Cu²⁺ but fails to reduce Ag⁺. This question tests deep conceptual understanding of the relative positions in the electrochemical series and the transitive nature of reduction potential comparisons.
This hard difficulty chemistry question is from the chapter redox reactions and electrochemistry, covering the topic of electrochemical series. It appeared in the 2025 exam.
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