Ozone naturally forms in the atmosphere whenever O₂ is irradiated by uv light or subjected to electrical discharges. On bright sunny days, we can notice the fresh - air smell of diluted ozone,. Which is around electrical equipment, however, ozone often occurs in higher concentration and has a disagreeable odor.
Although ozone is naturally occurring at ground level and ingredient of photochemical smog, it is a an essential component of the stratosphere, which occurring at 10 to 15 kilometers above ground level. Ozone is the stratosphere absorbs by ultraviolet radiation between 200 to 300 nanometer, which is actually virtually important to life on earth. Radiations from the sun contains uv rays that are harmful to the DNA of biological organism. Generally oxygen O₂, absorbs the most energetic of these uv rays in the earth's upper atmosphere, but only ozone is occupying in the stratosphere absorbs and the remaining uv radiation that is destructive to life on the earth.
Radiation 200 nanometer is absorbed in the upper atmosphere by O₂. Uv radiation between 200 and 300 nanometer is absorbed by O₃ in the stratosphere.
F. Sherwood Rowland and Mario J. Molina expressed concern that chlorofluorocarbons ( CFCs) such as CCl₂F₂ and CClF₃ , would be a source of chlorine atoms that could catalyze the decomposition of ozones in the stratosphere because that the ozone would be destroyed faster than it could be produced.
The CFCs are relatively inert compounds used as refrigerants, and spray - can propellants, blowing agents. The CFCs concentrate in the atmosphere where they steadily rise into the stratosphere. Once they are in the stratosphere and uv light decomposes them to form chlorine atoms, which is react with ozone to form O₂ and ClO. The ClO molecules are generally react with oxygen atoms in the stratosphere to regenerate Cl atoms.
Cl(g) + O₃(ɡ) →ClO(ɡ)+ O₂(ɡ)
CIO(ɡ)+ O(ɡ) →CI(ɡ) +O₂(ɡ)
O₃(ɡ)+ O(ɡ)→2O₂(ɡ)
All this net results is the decomposition of ozone to dioxygen. Cl atoms are consumed in the first step but regenerates in the second. Thus Cl atoms are not using up, they function as a catalyst.
In 1985, researchers reported that the ozone over the Antarctica has been declined precipitously each spring for several years, although it's returned the following winter. In August 1987, expedition was assembled to begin flights through the "OZONE HOLE" with instruments. Researchers found that the ozone is a depleted in the stratosphere, chlorine monoxide (ClO) appears as expected if chlorine atoms are catalyzing the depletion. The chlorofluorocarbons are the suspected source of this Cl atoms and internationally they are being phased out of production. The Air conditioners and Refrigerator are nowadays use hydrofluorocarbons ( HFCs) such as R410A which is a mixture of CF₃CHF₂ and CH₂F₂.
1995 in October's Mario Molina, Sherwood and Paul Crutzen were awarded the Noble Prize in chemistry for their work on stratosphere and ozone depletion. Crutzen studied effect of the nitrogen oxides in catalyzing the decomposition of ozone.
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