Chlorofluorocarbons are inert, non-flammable compounds that are commonly used in aerosols, as refrigerants and in fire extinguishers. They are most commonly known for the ability to deplete ozone. For this reason, there use has been gradually phased out. Now most industries replace CFCs with Hydrofluorocarbons (HFCs) which contain no chlorine.
Initially, they were used because of their inert nature. Scientists thought that CFCs were very good propellents because they did not break down in the troposphere. However, CFCs are inert and thus have very long half life. They diffuse to the stratosphere. Here they are provided energy by the UV radiation from the sun. This causes them to split into radicals which react with ozone and convert it into oxygen molecules. One chlorine radical generated from a molecule of CFC can react with many ozone molecules:
Cl· + O3 → ClO· + O2
ClO· + O3 → Cl· + 2 O2
(Reaction in the first equation is repeated and the cycle continues for a long time)
This was named as the major cause for the ozone holes near the poles of the earth. Ozone protects earth from harmful UV radiations that come in from the sun. Thus, if the ozone layer is depleted, UV radiations reach the earth in large amounts. This increases risks for problems like skin cancer.
Initially, they were used because of their inert nature. Scientists thought that CFCs were very good propellents because they did not break down in the troposphere. However, CFCs are inert and thus have very long half life. They diffuse to the stratosphere. Here they are provided energy by the UV radiation from the sun. This causes them to split into radicals which react with ozone and convert it into oxygen molecules. One chlorine radical generated from a molecule of CFC can react with many ozone molecules:
Cl· + O3 → ClO· + O2
ClO· + O3 → Cl· + 2 O2
(Reaction in the first equation is repeated and the cycle continues for a long time)
This was named as the major cause for the ozone holes near the poles of the earth. Ozone protects earth from harmful UV radiations that come in from the sun. Thus, if the ozone layer is depleted, UV radiations reach the earth in large amounts. This increases risks for problems like skin cancer.
