In which of the following reactions, $\mathrm{H}_2 \mathrm{O}_2$ acts as a reducing reagent?

1. $\mathrm{PbO}_2(s)+\mathrm{H}_2 \mathrm{O}_2(a q) \longrightarrow \mathrm{PbO}(s)+\mathrm{H}_2 \mathrm{O}(l)+\mathrm{O}_2(g)$
2. $\mathrm{Na}_2 \mathrm{SO}_3(a q)+\mathrm{H}_2 \mathrm{O}_2(a q) \longrightarrow \mathrm{Na}_2 \mathrm{SO}_4(a q)+\mathrm{H}_2 \mathrm{O}(l)$
3. $2 \mathrm{KI}(a q)+\mathrm{H}_2 \mathrm{O}_2(a q) \longrightarrow 2 \mathrm{KOH}(a q)+\mathrm{I}_2(s)$
4. $\mathrm{KNO}_2(a q)+\mathrm{H}_2 \mathrm{O}_2(a q) \longrightarrow \mathrm{KNO}_3(a q)+\mathrm{H}_2 \mathrm{O}(l)$

Solution

Asked in: AP EAMCET 2001

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