Question

How does ${{H}_{2}}{{O}_{2}}$ act as a bleaching agent?

Answer 1

Hint: The crucial key to answering this question is to remember that ${{H}_{2}}{{O}_{2}}$ is an excellent oxidising agent. With this information in mind, try and solve the given question.
Complete answer:
Let us first look into ${{H}_{2}}{{O}_{2}}$ as a compound before trying to analyse it bleaching action.
Hydrogen peroxide is a chemical compound with the formula ${{H}_{2}}{{O}_{2}}$. In its pure form, it is a very pale blue liquid, slightly more viscous than water. Hydrogen peroxide is the simplest peroxide. It is used as an oxidizer, bleaching agent, and antiseptic.
Hydrogen peroxide acts as both a reducing and an oxidizing agent.
When ${{H}_{2}}{{O}_{2}}$ serves as an oxidizing agent, the oxygen of hydrogen peroxide (that is present in -1 oxidation state) is reduced to water (-2 oxidation state).
\[\] \[{{H}_{2}}{{O}_{2}}\text{ }+\text{ }2{{H}^{+}}\text{ }+\text{ }2e{{\text{ }}^{}}\to \text{ }2{{H}_{2}}O\]
When ${{H}_{2}}{{O}_{2}}$ (-1 oxidation state) serves as a reducing agent, the oxygen of ${{H}_{2}}{{O}_{2}}$ is oxidized to O2 ( 0 oxidation state) and bubbles are noticed. As a reducing agent:
\[2\text{ }Mn{{O}_{4}}^{-}\text{ }+\text{ }5\text{ }{{H}_{2}}{{O}_{2}}\text{ }+\text{ }6\text{ }{{H}^{+}}\to \text{ }5\text{ }{{O}_{2}}\text{ }+\text{ }2\text{ }M{{n}^{2-}}\text{ }+\text{ }8{{H}_{2}}O\]
Now, with all this in mind, let us now analyse the bleaching action of Hydrogen Peroxide.
Since Hydrogen Peroxide is highly reactive in nature, it is most commonly used as a bleaching agent. Other Bleaching agents such as Hypochlorite solution are also used (Industrially) but Hydrogen peroxide is more earth friendly.
Hydrogen peroxide works by breaking the chemical bonds of a chromophore (part of a molecule that has colour). This changes the molecule so that it either has no colour or else reflects colour outside the visible spectrum.

Note:
${{H}_{2}}{{O}_{2}}$ contains peroxy bond, on exposing to air or any friction or any disturbing actions it decomposes to water and oxygen free radical, this oxygen free radical is highly reactive, this on reacting to form stable compound which releases large amount of energy which kills bacteria and other harmful microorganisms.