1.

20 ml of solution having 0.2 g of impure H2O2 reacts with 0.316 of KMnO4 in acidic medium. Calculate (a) Purity of H2O2 (b) Volume of dry oxygen evolved at 0°C and 750 mm pressure.

Answer»

2MnO4-(aq) + 6H+(aq) + 5H2O2(aq) → 2Mn2+(aq) + 8H2O(l) + 50(g)

158 x 2 g of KMnO4 reacts with 34 × 5 g of H2O2

0.316 g of KMnO4 will react with \(\frac{170}{0.2}\) x 0.316 g of H2O2 = 0.169 g of H2O2

⇒ Percentage purity of H2O2\(\frac{0.169}{0.2}\) x 100 = 85%

Also 316 g of KMnO4 at STP produces 5 × 22 L of O2

⇒ 0.316g of KMnO4 at STP will produce \(\frac{5\times 22.4}{316}\) x 0.316 

= 0.112 L of O2

Conversion to 750 mm pressure 760 x 0.112 = x × 750x = 0.113 L



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