Question

What is the ozone hole and how it is caused?

Answer 1

Hint: the ozone layer protects the earth from the hazardous ultraviolet radiation by absorbing these radiations. The thinning of the layer causes a serious health hazard like skin cancer. This is due to the presence of CFCs in the atmosphere released by aerosols, propellants, etc.

Complete step by step answer:
The ozone layer acts as the protection layer for the earth. It trapped the UV radiation coming from the sun.
The Chlorofluorocarbons (CFCs) emitted by the refrigerators, air conditioning units, sprays, etc. contain the chlorine, fluorine, and carbon atoms. This molecule reaches the high altitude where the ozone layer is situated. This molecule reacts with the highly energetic photons in the ozone layer resulting in the depletion of ozone from the ozone layer.
The region of the depletion of ozone in the ozone layer is called the ozone hole. Though it is a region it is still termed as the hole. This region is over Antarctica. The increase in heat and depletion of ozone around the Earth's Polar Regions is called the ozone hole.
Chlorine from the CFCs acts as a catalyst and initiates the breakdown of ozone. It combines with the nascent oxygen formed and destroys the ozone cycle. As the ozone molecules are broken down they are now unable to absorb the UV radiations and we experience the intense UV radiation on the earth surface. This radiation further becomes the major reason for global warming.
The reactions associated with the attack of CFCs on the ozone are as follows:
\[\begin{matrix}
 \text{X + }{{\text{O}}_{\text{3}}}\text{ }\to \text{XO + }{{\text{O}}_{\text{2}}} \\
 {{\text{O}}_{\text{3}}}\text{ + }\left[ \text{O} \right]\text{ }\to \text{ 2 }{{\text{O}}_{\text{2}}} \\
   \left[ \text{O} \right]\text{ + XO }\to \text{X + }{{\text{O}}_{\text{2}}} \\
   {} \\
\end{matrix}\]
In the above reaction X can be an atom or molecule which acts as a catalyst to convert the ozone to${{\text{O}}_{\text{2}}}$. Chlorine as an X initiates the breakdown of the ozone to free a two oxygen molecules
Most of the time the X is CFCs which does not change in the net reaction and continues to destroy the ozone layer.
The scientists have observed an ozone hole over the arctic which has the maximum extension of less than 1 million square kilometre. There is also a big hole over Antarctica which has a size of about 20 to 25 million square kilometre.


Note: One will have a question about how chlorine reaches such high altitude. The chlorine is the major component of chlorofluorocarbon which is produced from the air conditioners, refrigerators, sprays, etc. They are very stable and have a lifetime of 100 years. The wind carries it to the ozone layer. One chlorine can destroy a thousand molecules of ozone. This reaction of ozone destruction is continuous. Ozone depletion is a serious problem for earth.