How Fe³⁺ catalyses the iodide–peroxodisulphate reactionFe³⁺ आयोडाइड–पेरॉक्सोडाइसल्फ़ेट अभिक्रिया को कैसे उत्प्रेरित करता हैHow Fe³⁺ catalyses the iodide–peroxodisulphate reaction

Class 12 Chemistry · Chapter 4 · interactive diagram

Parts and what they mean

• Iron(III) (आयरन(III)) — The catalyst. It is used up in step 1 and regenerated in step 2.
• Iron(II) (आयरन(II)) — Intermediate form of the catalyst.
• Step 1: 2Fe³⁺ + 2I⁻ → 2Fe²⁺ + I₂ (चरण 1: 2Fe³⁺ + 2I⁻ → 2Fe²⁺ + I₂) — Two cations meet two anions easily — much faster than two anions (I⁻ and S₂O₈²⁻) meeting directly.
• Step 2: 2Fe²⁺ + S₂O₈²⁻ → 2Fe³⁺ + 2SO₄²⁻ (चरण 2: 2Fe²⁺ + S₂O₈²⁻ → 2Fe³⁺ + 2SO₄²⁻) — Peroxodisulphate turns Fe²⁺ back into Fe³⁺, ready for the next cycle.
• Overall reaction (कुल अभिक्रिया) — Add steps 1 and 2: iron cancels. Atoms and charge balance (−4 = −4).

Steps

1. Fe³⁺ is the catalyst; Fe²⁺ is its intermediate form.
2. Step 1: Fe³⁺ oxidises iodide to iodine and becomes Fe²⁺.
3. Step 2: peroxodisulphate oxidises Fe²⁺ back to Fe³⁺.
4. Overall: 2I⁻ + S₂O₈²⁻ → I₂ + 2SO₄²⁻; iron is regenerated.

Original diagram drawn by Simple Learning Hub, based on the NCERT textbook. Report a mistake