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The standard reduction potentials for Zn²⁺/Zn, Ni²⁺/Ni and Fe²⁺/Fe are -0.76, -0.23 and -0.44 V respectively. The reaction X + Y²⁺ → X²⁺ + Y will be spontaneous when :

1. X = Ni, Y = Fe
2. X = Ni, Y = Zn
3. X = Fe, Y = Zn
4. X = Zn, Y = Ni

Correct answer: X = Ni, Y = Zn

Solution

The reaction is spontaneous when the reduction potential of the oxidizing agent (Y²⁺) is higher than that of the reducing agent (X). In this case, Ni has a higher reduction potential than Zn, making the reaction Ni + Zn²⁺ → Ni²⁺ + Zn favorable.

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