Identify the hydrated blue salt which when treated with KI solution, a brown solution is obtained which becomes colourless when treated with hypo solution.

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The hydrated blue salt is copper(II) sulfate pentahydrate, CuSO₄·5H₂O. When treated with KI, Cu²⁺ oxidizes I⁻ to I₂ (brown solution). Hypo (Na₂S₂O₃) reduces I₂ back to I⁻, making the solution colorless.

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$2 CuSO_{4} + 4 KI \to Cu_{2} I_{2} + I_{2} + 2 K_{2} SO_{4}$

$I_{2} + 2 Na_{2} S_{2} O_{3} \to 2 NaI + Na_{2} S_{4} O_{6}$

Chemistry - Redox Reactions Question with Solution | TestHub

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