Question

Explain the bleaching action of ozone.

Answer 1

Hint- The bleaching action of ozone is because of its oxidation power. Ozone acts as the strong bleaching agent. Ozone has the capability to provide oxygen as well as the nascent oxygen. This production of nascent oxygen actually causes the bleaching action as it bleaches the color on a permanent basis.

Complete answer:
Ozone is a very strong oxidizing agent and the biggest challenge in using it to bleach wood pulp. Ozone can react with sites of unsaturation including those within aromatic rings.
And also, it is a good reagent to allow pulp to be bleached without any chlorine-containing chemicals i.e., totally chlorine free.
Physical properties:
Ozone is a blue in colour and also it is slightly soluble in water and much more soluble in inert non-polar solvents such as carbon tetrachloride or fluorocarbons, where it forms a blue solution.
It can be easily detected at about 0.01 ppm of ozone in air where it has a very specific sharp odor.
As we know oxidizing action of ozone is very fast, it acts as a mild bleaching agent as well as a sterilizing agent. It acts as a bleaching agent for many vegetables coloring matter.
It is taken as a strong oxidizing agent because of mainly the ease with which it gives out atoms of nascent oxygen. It helps in oxidizing:
Vegetable colouring matter + ${{\text{O}}_{\text{3}}}$ —> Oxidized coloured matter + ${{\text{O}}_2}$
(Colourless)
For example, ivory, litmus, delicate fabrics etc. are bleach by Ozone.
Remember that Ozone is toxic even at low concentrations and at high concentrations it can explode. The concentration of ozone gas in air needs to be monitored continuously. And also, Temperature, pH, consistency, and mixing all impact the efficiency and selectivity of ozone bleaching.

Note- Always remember that Bleaching action of ozone is based on oxidation while that of Sulphur is based on reduction. Or we say Sulphur dioxide is a temporary bleaching agent. And also, Ozone produces oxygen and nascent oxygen. This nascent oxygen bleaches the colour permanently.