how CFC's harm the ozone layer ?pls explain ...
Your friend has answered correctly, I would like to add more points
The Cl atoms of chlorofluoro carbons can destroy ozone molecules through a variety of catalytic cycles. In the simplest example of such a cycle, a chlorine atom reacts with an ozone molecule, taking an oxygen atom with it (forming ClO) and leaving a normal oxygen molecule. The chlorine monoxide (i.e., the ClO) can react with a second molecule of ozone (i.e., O3) to yield another chlorine atom and two molecules of oxygen. The chemical shorthand for these gas-phase reactions is:
Cl + O3 → ClO + O2 – The chlorine atom changes an ozone molecule to ordinary oxygen
ClO + O3 → Cl + 2O2 – The ClO from the previous reaction destroys a second ozone molecule and recreates the original chlorine atom, which can repeat the first reaction and continue to destroy ozone.
The overall effect is a decrease in the amount of ozone.
CFCs are man-made chemicals that have been in production for more than a half century. These chlorine containing substances are found in refrigerant, aerosols, and solvents. Due to their long lifetimes and the fact that they do not wash away in rain, it is possible for CFCs to rise up into the ozone layer above the earth, where they eventually break down due to exposure to ultraviolet radiation. As they decompose, they release chlorine and bromine into the ozone layer. These two chemicals are responsible for damaging and depleting the ozone layer. For every one chlorine atom that is released into the ozone layer, 100,000 ozone molecules are destroyed. Thus, the CFCs cause the ozone layer to break down faster than it can replace itself.
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