In which of the following reactions, oxygen is not liberated?

In which of the following reactions, oxygen is not liberated?
  1. Reaction of $\mathrm{HOCl}$ with $\mathrm{H}_2 \mathrm{O}_2$
  2. Reaction of acidified $\mathrm{KMnO}_4$ with $\mathrm{H}_2 \mathrm{O}_2$
  3. Reaction of iodine with $\mathrm{H}_2 \mathrm{O}_2$ in basic medium
  4. Reaction of lead sulphide with $\mathrm{H}_2 \mathrm{O}_2$

Solution

(i) $2 \mathrm{HOCl}+\mathrm{H}_2 \mathrm{O}_2 \longrightarrow 2 \mathrm{H}_2 \mathrm{O}+\mathrm{Cl}_2(g)+\mathrm{O}_2(g)$ (ii) $3 \mathrm{H}_2 \mathrm{O}_2+2 \mathrm{KMnO}_4 \longrightarrow 3 \mathrm{O}_2+2 \mathrm{MnO}_2$ $+2 \mathrm{KOH}+2 \mathrm{H}_2 \mathrm{O}$ (iii) $\mathrm{H}_2 \mathrm{O}_2+\mathrm{I}_2 \longrightarrow 2 \mathrm{HI}+\mathrm{O}_2$ (iv) $\mathrm{PbS}+4 \mathrm{H}_2 \mathrm{O}_2 \rightarrow \mathrm{PbSO}_4+4 \mathrm{H}_2 \mathrm{O}$

Asked in: AP EAMCET 2018 (23 Apr Shift 2)

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