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Question
Transition metals can act as catalysts because these can change their oxidation state. How does \[\ce{Fe(III)}\] catalyse the reaction between iodide and persulphate ions?
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Solution
Reaction between iodide and persulphate ions is:
\[\ce{2I^{-} + S2O^{2-}8 ->[Fe(III)] I2 + 2SO^{2-}4}\]
Role of \[\ce{Fe(III)}\] ions:
\[\ce{2Fe^{3+} + 2I^{-} -> 2Fe^{2+} + I2}\]
\[\ce{2Fe^{2+} + S2O^{2-}8 -> 2Fe^{3+} + 2SO^{2-}4}\]
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