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E° values for Mn³⁺/Mn²⁺ (+1.57 V), Co³⁺/Co²⁺ (+1.97 V) and Fe³⁺/Fe²⁺ (+0.77 V). Which is the strongest oxidising agent (M³⁺ → M²⁺)?
ACo³⁺ (highest positive E°)
BMn³⁺
CAll equal
DFe³⁺
Answer & Solution
Correct answer: A. Co³⁺ (highest positive E°)
**Most positive E°(M³⁺/M²⁺) = strongest oxidising agent**: **Co³⁺ (+1.97 V) > Mn³⁺ (+1.57 V) > Fe³⁺ (+0.77 V)**. Co³⁺ is so strongly oxidising it reacts with water unless stabilised by ligands like NH₃ ([Co(NH₃)₆]³⁺).
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