Q11 / 125 · BITSAT 2010 · Chemistry

In which of the following reactions, $\mathrm{H}_{2} \mathrm{O}_{2}$ is acting as a reducing agent?

  • A
    $\mathrm{H}_{2} \mathrm{O}_{2}+\mathrm{SO}_{2} \rightarrow \mathrm{H}_{2} \mathrm{SO}_{4}$
  • B
    $2 \mathrm{KI}+\mathrm{H}_{2} \mathrm{O}_{2} \rightarrow 2 \mathrm{KOH}+\mathrm{I}_{2}$
  • C
    $\quad \mathrm{PbS}+4 \mathrm{H}_{2} \mathrm{O}_{2} \rightarrow \mathrm{PbSO}_{4}+4 \mathrm{H}_{2} \mathrm{O}$
  • Correct answer
    D
    $\mathrm{Ag}_{2} \mathrm{O}+\mathrm{H}_{2} \mathrm{O}_{2} \rightarrow 2 \mathrm{Ag}+\mathrm{H}_{2} \mathrm{O}+\mathrm{O}_{2}$

Solution

$\mathrm{SO}_{2}$ changes to $\mathrm{H}_{2} \mathrm{SO}_{4}$ (O.N. changes from +4 to +6 oxidation $)$ $2 \mathrm{KI} \rightarrow \mathrm{I}_{2}(\mathrm{O} . \mathrm{S} .$ changes from -1 to 0 oxidation) $\mathrm{PbS} \rightarrow \mathrm{PbSO}_{4}(\mathrm{O} . \mathrm{S}$. changes from -2 to +6 oxidation) $\mathrm{Ag}_{2} \mathrm{O} \rightarrow 2 \mathrm{Ag}(\mathrm{O} . \mathrm{S} .$ changes from +1 to 0 reduction)

Hence, the correct answer is option: 'D'.

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