25 ml of H2O2 solution were added to excess of acidified solution of KI and iodine so liberated required 20 ml of 0.1 N Na2S2O3 for titration. The normality H2O2 is ?

Q: 25 ml of H2O2 solution were added to excess of acidified solution of KI and iodine so liberated required 20 ml of 0.1 N Na2S2O3 for titration. The normality H2O2 is ?

(A) 0.02

(B) 0.04

(C) 0.08

(D) 0.03

Sol:

O2–1 + 2e → 2O–2                   2 + S2O32–  → 2I + S4O62–

2I  → I2 + 2e

Meq. of H2O2  = Meq. of I2 = Meq of Na2S2O3

N × 25 = 0.1 × 20

$N_{H_2 O_2} = 0.08 $

Ans: (C)