Question

Explain the relationship between CFCS and ozone in the stratosphere.

Answer 1

Hint:A layer of the Earth's atmosphere is the stratosphere. When you go upward, it is the second layer of the atmosphere. Right under the stratosphere is the troposphere, the lowest layer.

Complete answer:
>Ozone depletion consists of two related events observed since the late 1970s: a gradual decline of about four percent in the overall amount of ozone in the atmosphere of the Earth (the ozone layer) and a much greater decrease in stratospheric ozone in the early 1970s around the polar regions of the Earth.
>Aside from these stratospheric occurrences, there are also springtime polar tropospheric ozone depletion occurrences.
>Manufactured chemicals, in particular manufactured halocarbon refrigerants, solvents, propellants, and foam-blowing agents (chlorofluorocarbons (CFCs), HCFCs, halons), referred to as ozone-depleting substances (ODS), are the primary causes of ozone depletion and the ozone hole.
>Through turbulent mixing after being released from the atmosphere, these compounds are transported into the stratosphere, mixing much quicker than the molecules can settle.
>They release halogen atoms by photodissociation once they are in the stratosphere, catalysing the breakdown of ozone$ (O_3)$ into oxygen $(O_2)$. Both forms of ozone depletion have been shown to rise as halocarbon emissions have risen.
>Powerful ozone-depleting compounds are CFCs or Chlorofluorocarbons. They stay for a long period of time in the atmosphere. From the troposphere, they enter the stratosphere, disintegrating slowly through the action of UV radiation and thus releasing Cl, causing ozone depletion as follows:
In the case of UV-rays,
$CFCl_3 \rightarrow CFCl_2+Cl$
$CF_2Cl_2 \rightarrow CF_2Cl+Cl$
This Cl reacts with $O_3$ and convert it into $O_2$
$Cl+O_3 \rightarrow ClO+O_2$
$ClO+O_2+O_3$
In a year, one chlorine atom will theoretically kill over 60,000 $O_3$ molecules.
So, the ozone layer is seriously harmful to CFCs.

Note:At medium latitudes, the bottom of the stratosphere is about 10 km (6.2 miles, or about 33,000 feet) above the earth. At an altitude of 50 km (31 miles), the tip of the stratosphere appears. With latitude and with seasons, the height of the bottom of the stratosphere varies. The lower boundary of the stratosphere at the equator can be as high as 20 km (12 miles or 65,000 feet) and as low as 7 km (4 miles or 23,000 feet) in winter at the poles.