Which of the following is the correct order of standard electrode potentials (in increasing order of reduction potential) for the couples Fe³⁺/Fe²⁺, Cu²⁺/Cu and Zn²⁺/Zn?

Step-by-step solution

1. List standard potentials: Fe³⁺/Fe²⁺ = +0.77 V, Cu²⁺/Cu = +0.34 V, Zn²⁺/Zn = –0.76 V.
2. Arrange them from lowest to highest: –0.76 V < +0.34 V < +0.77 V.
3. Identify the corresponding couples: Zn²⁺/Zn < Cu²⁺/Cu < Fe³⁺/Fe²⁺.
4. Choose the option that matches this order.

Concept tested: Comparison of standard electrode potentials

Published 1 September 2026 · How this solution was prepared and checked

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