JEE Main · 2026 · 22 Jan 2026 · Shift 2 · Redox Reactions and Electrochemistry

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Consider the following electrochemical cell:

The pH above which, oxygen gas would start to evolve at anode is _____ (nearest integer).
[Given: , (standard reduction potential) and at the given condition]

Answer: 4

Solution

Oxygen begins to evolve at the anode when the cell becomes spontaneous, that is when . The cathode has V, while the anode half-reaction at bar has . Setting gives , so . Oxygen starts to evolve above a pH of .

JEE Main · 2026 · 22 Jan 2026 · Shift 2 · Integer answer

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