CBSE Class 12 · 2011 · Delhi · d and f Block ElementsShort Answer

Complete the following chemical equations:
i) MnO₄⁻ + C₂O₄²⁻ + H⁺ →
ii) KMnO₄ (heated) →
iii) Cr₂O₇²⁻ + H₂S + H⁺ →

Answer: (i) 2MnO₄⁻+5C₂O₄²⁻+16H⁺→2Mn²⁺+10CO₂+8H₂O. (ii) 2KMnO₄ →Δ→ K₂MnO₄+MnO₂+O₂. (iii) Cr₂O₇²⁻+3H₂S+8H⁺→2Cr³⁺+3S+7H₂O.

Solution

(i)

2Mn O_{4}^{-} + 5 C_{2} O_{4}^{2 -} + 16 H^{+} \to 2M n^{2 +} + 10C O_{2} + 8 H_{2} O

(ii) On heating, permanganate decomposes:

2KMn O_{4} Δ K_{2} Mn O_{4} + Mn O_{2} + O_{2}

(iii) Dichromate oxidises H

_{2}

S to sulphur:

C r_{2} O_{7}^{2 -} + 3 H_{2} S + 8 H^{+} \to 2C r^{3 +} + 3S ↓ + 7 H_{2} O

CBSE Class 12 Board · 2011 · Delhi · Subjective