Question

Which of the following reactions, hydrogen peroxide acts as an oxidizing agent?
a)$HOCl + H{}_2O{}_2 \to H{}_3O{}^ + + Cl{}^ - + O{}_2$
b)$HOCl + H{}_2O{}_2 \to H{}_3O{}^ + + Cl{}^ - + O{}_2$
c)$PbS + 4H{}_2O{}_2 \to PbSO{}_4 + 4H{}_2O$
d)$I{}_2 + H{}_2O{}_2 + 2OH{}^ - \to 2I{}^ - + 2H{}_2O + O{}_2$

Answer 1

This question is purely based on the basics of the process of oxidation and reduction. Knowing the oxidation number of the given compound in the given reaction and finding out which process took place will help you find the correct answer

Complete step by step answer:
Oxidising agents are the species which help other species to oxidise and itself goes under reduction. So what we have to do is find the reaction in which hydrogen peroxide goes under reduction. Reduction is decrease in oxidation number or gain of electron.
In case of first option, hydrogen peroxide is changed to oxygen that means the oxidation number is increased. Oxidation is taking place here so the correct option cannot be option one
In case of the second option again hydrogen peroxide is changed to oxygen where oxidation takes place so this cannot be the correct option too.
In case of third option, the reaction of lead sulphide the oxidation number is $+ 2$ and the oxidation number of lead sulphate is $+ 4$ so we can see the oxidation number is increased. Increased oxidation number indicates the process of oxidation took place. As discussed above hydrogen peroxide will be considered as an oxidising agent when it will help other species in oxidation. Here in this reaction hydrogen peroxide helped lead sulphide in oxidation so concluding that option C did the correct answer.

In option C hydrogen peroxide is used as an oxidising agent.

Note: lead sulphide reacts with hydrogen peroxide to produce lead sulphate and water products. It is a redox reaction. In the given reaction the sulphide ion is oxidized to give sulphate ions. The oxidation number of sulphur is increased from $- 2$ to $+ 6$