8.25 Describe the oxidising action of potassium dichromate and write the ionic equations for its reaction with: (i) iodide (ii) iron(II) solution and (iii) H₂S

<p><strong>8.25 </strong>K₂Cr₂O₇ acts as a very strong oxidizing agent in acidic medium. K₂Cr₂O₇ gets reduced and acts as an oxidizing agent by oxidizing Iodide to iodine</p><p><strong>(i)</strong> K₂Cr₂O₇ oxidizes iodide to iodine</p><p>Cr₂O₇^2-+ 14H⁺+ 6e^-→ 2Cr³⁺ + 7H₂O</p><p>2I^-→ I₂ + 2e^- } x3</p><p>Overall: Cr₂O₇^2-+ 14H⁺+ 6I^-→ 2Cr³⁺ + 7H₂O+ 3I₂</p><p><strong>(ii)</strong> K₂Cr₂O₇ oxidizes iron(II) to iron(III)</p><p>Cr₂O₇^2-+ 14H⁺+ 6e^-→ 2Cr³⁺ + 7H₂O</p><p>Fe²⁺→ Fe³⁺ + e^- } x6</p><p>Overall: Cr₂O₇^2-+ 14H⁺+ 6Fe²⁺→ 2Cr³⁺ + 7H₂O + 6Fe³⁺</p><p><strong>(iii)</strong> K₂Cr₂O₇ oxidized H₂S to sulphur</p><p>Cr₂O₇^2-+ 14H⁺+ 6e^-→ 2Cr³⁺ + 7H₂O</p><p>H₂S → S + 2H⁺ + 2e^-} x3</p><p>Overall: Cr₂O₇^2-+ 8H⁺+ 3H₂S → 2Cr³⁺ + 7H₂O +3S</p>

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