CBSE Class 12 · 2011 · All India · d and f Block ElementsShort Answer

Complete the following chemical equations:
i) MnO₄⁻(aq) + S₂O₃²⁻(aq) + H₂O(l) →
ii) Cr₂O₇²⁻(aq) + Fe²⁺(aq) + H⁺(aq) →

Answer: (i) 8MnO₄⁻+3S₂O₃²⁻+H₂O→8MnO₂+6SO₄²⁻+2OH⁻. (ii) Cr₂O₇²⁻+6Fe²⁺+14H⁺→2Cr³⁺+6Fe³⁺+7H₂O.

Solution

(i) In neutral/faintly alkaline medium permanganate oxidises thiosulphate to sulphate, itself reduced to MnO

_{2}

8Mn O_{4}^{-} + 3 S_{2} O_{3}^{2 -} + H_{2} O \to 8Mn O_{2} + 6S O_{4}^{2 -} + 2O H^{-}

(ii)

C r_{2} O_{7}^{2 -} + 6F e^{2 +} + 14 H^{+} \to 2C r^{3 +} + 6F e^{3 +} + 7 H_{2} O

CBSE Class 12 Board · 2011 · All India · Subjective