Question

Which of the following chemicals is mainly responsible for ozone depletion?
1. Chlorofluorocarbon
2. Polyphenol
3. Dioxin
4. None of the above

Answer 1

Correct Answer - Option 1 : Chlorofluorocarbon

Concept:

Ozone Layer: 

• Ozone (O3) is a molecule formed by three atoms of oxygen. Ozone is a deadly poison.
• Ozone is found in the stratosphere layer of the atmosphere.
• However, at the higher levels of the atmosphere, ozone performs an essential function. It shields the surface of the earth from ultraviolet (UV) radiation from the Sun.
• This radiation is highly damaging to organisms, for example, it is known to cause skin cancer in human beings or can split the DNA.
• It is a pale blue gas with a distinctively pungent smell.
• Ozone is an excellent oxidizing agent as it breaks down into oxygen gas and nascent oxygen. { O3 → O2 + [O] }
• It is an allotrope of oxygen that is much less stable than the diatomic allotrope O2, breaking down in the lower atmosphere to O2 or di-oxygen

Its depletion:

• The amount of ozone in the atmosphere began to drop sharply in the 1980s.
• This decrease has been linked to synthetic chemicals like chlorofluorocarbons (CFCs) which are used as refrigerants and in fire extinguishers.
• The government bans those products which contain CFCs.

• Ozone is thermodynamically unstable and decomposes to molecular oxygen. Thus, a dynamic equilibrium exists between the production and decomposition of ozone molecules

Explanation:​

• In recent years, there have been reports of the depletion of this protective ozone layer because of the presence of certain chemicals in the stratosphere.
• The main reason for ozone layer depletion is believed to be the release of chlorofluorocarbon compounds (CFCs), also known as Freons.
• These compounds are non-reactive, non-flammable, non-toxic organic molecules and therefore used in refrigerators, air conditioners, in the production of plastic foam and by the electronic industry for cleaning computer parts etc.
• Once CFCs are released in the atmosphere, they mix with the normal atmospheric gases and eventually reach the stratosphere
• In the 1980s, for the first time, atmospheric scientists working in Antarctica reported about the depletion of the ozone layer commonly known as ozone hole over the South Pole.

• Greenhouse effect:
  • The greenhouse effect is a natural phenomenon that warms the surface of the Earth.
  •  As the Sun's energy enters the Earth's atmosphere, part of it is reflected back in space and the remainder is absorbed and re-radiated by greenhouse gases.  
  • The radiation consumed warms the atmosphere and the Earth's surface.
• Acid Rain:
  • As the name suggests, acid rain may be said to be the easiest way to precipitate acid in the form of rain.
  • This results in acid rain as air contaminants such as nitrogen oxides and sulphur react with rainwater and come down with the rain.
• Smog:
  • The term smog means a mixture of fog and smoke.
  • ​It is a type of air pollution that occurs in many cities worldwide.