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Ozone depletion and ozone hole: Definition, explanation, chemical reactions,

Question: What is ozone hole?  Describe ozone formation and ozone depletions with chemical reactions.

Answer.

Ozone hole

The region in the atmosphere where amount of  ozone has been reduced is known as ozone hole. 

Ozone Formation

Ozone (O3) is important component of stratosphere that protects living things from harmful ultraviolet radiations. Otherwise, these radiations are dangerous to mankind, animals and plants. 

In upper atmosphere, ozone molecules absorb UV radiations and undergo breaking and reformation along with release of heat.


In the absence of external interference both breaking and formation rates of O3 are equal. Human activities discharge certain chemicals such chlorofluorocarbons (CFCs) which disturb this natural balance.

Ozone Depletion

The gradual decrease in thickness of ozone layer in upper atmosphere due to human activities is called ozone depletion.

CFCs are used in refrigerators, room air conditioner and aerosol cans. These gases are highly volatile and do not react with other compounds in troposphere. 
These gases diffuse into stratosphere where these molecules generate free chlorine radicals in presence of UV radiations.
These free chlorine radicals react with ozone to form chlorine monoxide and oxygen gas. ClO further react with atomic oxygen produced during breaking of ozone molecule.
Chlorine radical is regenerated and reacts with thousands of ozone molecules again and again. 
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