Questions & Answers

The bleaching action of \[{{\text{H}}_{\text{2}}}{{\text{O}}_{\text{2}}}\] is due to which one of the following reactions:
A.\[PbS{\text{ }} + {\text{ }}4{H_2}{O_2}{\text{ }} \to {\text{ }}PbS{O_4}{\text{ }} + {\text{ }}4{H_2}O\]
B.\[{H_2}{O_2}{\text{ }} \to {\text{ }}{H_2}O{\text{ }} + {\text{ }}[O]\]
C.\[{H_2}{O_2}{\text{ }} + {\text{ }}[O]{\text{ }} \to {\text{ }}{H_2}O{\text{ }} + {\text{ }}{O_2}\]
D.\[{H_2}{O_2}{\text{ }} + {\text{ }}{O_3}{\text{ }} \to {\text{ }}{H_2}O{\text{ }} + {\text{ }}2{O_2}\]

Answer Verified Verified
Hint: The bleaching action is a process that involves reduction of the bleaching agent, thereby removing oxygen from the coloured substance and makes it colourless.

Complete step by step answer:
-Hydrogen oxide acts as a bleaching agent as it releases nascent oxygen which has a powerful oxidizing effect that destroys some microbes such as bacteria. It is also used as an oxidizer and antiseptic.
-The mechanism behind this antibacterial action is that the peroxy bond of hydrogen peroxide undergoes bond dissociation in presence of light and decomposes to water and nascent oxygen. This oxygen free radical is very reactive and forms a stable compound by reacting with other species, which results in release of a large amount of energy that kills bacteria and harmful microbes.
 The perhydroxyl anion (\[{\text{H}}{{\text{O}}_{\text{2}}}^{\text{ - }}\]) is the active bleaching species.
-This in turn explains bleaching action of hydrogen peroxide and the correct reaction is-
\[{H_2}{O_2}{\text{ }} \to {\text{ }}{H_2}O{\text{ }} + {\text{ }}[O]\]

Hence, the correct option is (B).

One drawback is that hydrogen peroxide needs alkaline conditions and suitably elevated temperatures to be effective. Also, it is highly environment friendly as it decomposes to oxygen and water.