In which of the following reactions the hydrogen peroxide acts as a...

$PbS + 4{H}_{2}{O}_{2} \to {PbSO}_{4} + 4{H}_{2}O$

In the above reaction lead sulphide oxidised to lead sulphate. Hence, hydrogen peroxide acts as oxidising agent.

$2{Fe}^{2 +} + {H}_{2}{O}_{2} \to 2{Fe}^{3 +} + 2{OH}^{-}$

In the above reaction ${Fe}^{2 +}$ oxidised to ${Fe}^{3 +}$. Hence, hydrogen peroxide acts as oxidising agent.

${Mn}^{2 +} + {H}_{2}{O}_{2} \to {Mn}^{4 +} + 2{OH}^{-}$

In the above reaction ${Mn}^{2 +}$ oxidised to ${Mn}^{4 +}$. Hence, hydrogen peroxide acts as oxidising agent.

$HOCl + {H}_{2}{O}_{2} \to {H}_{3}{O}^{+} + {Cl}^{- 1} + {O}_{2}$

In the above reaction ${Cl}^{+ 1}$ reduced to ${Cl}^{-}$, hence, hydrogen peroxide acts as a reducing agent.