Question

State the harmful effect of Chlorofluorocarbon.

Answer 1

Hint:
(i) Atmospheric pollution can be caused by gaseous pollutants like carbon monoxide, carbon dioxide, sulfur trioxide, sulfur dioxide, nitrogen oxide, nitrogen dioxide etc. In addition to these common pollutants, there are also some specific pollutants such as chlorofluorocarbons or CFC which are ejected into the atmosphere from industrial processes.
(ii) Chlorofluorocarbons or CFCs are partially of fully halogenated hydrocarbons that contain carbon, hydrogen, chlorine and fluorine.

Complete step by step answer:
CFCs are generally produced by exchange of halogens from chlorinated methanes and ethanes. For example, the CFC chlorodifluoromethane from chloroform is:
\[{\text{HCC}}{{\text{l}}_{\text{3}}}{\text{ + 2HF}} \to {\text{HC}}{{\text{F}}_{\text{2}}}{\text{Cl + 2HCl}}\]
There are many harmful effects of CFCs. The most important harmful effect is the depletion of the ozone layer. CFCs are used in fridges, air conditioners, blowing foams etc. They are very stable on earth but when they slowly move to the stratosphere, intense UV radiation acts on their bonds and releases free chlorine radical which strips an atom from ozone molecule converting it into atomic oxygen. The process is repeated and in this way, one chlorine atom destroys thousands of ozone molecules.
\[
  {\text{C}}{{\text{F}}_{\text{3}}}{\text{Cl}}\xrightarrow{{{\text{hv}}}}\mathop {\text{C}}\limits^{\text{ \bullet }} {{\text{F}}_{\text{3}}}{\text{ + C}}{{\text{l}}^{\text{ \bullet }}} \\
  {{\text{O}}_{\text{3}}}{\text{ + C}}{{\text{l}}^{\text{ \bullet }}} \to {\text{Cl}}{{\text{O}}^{\text{ \bullet }}}{\text{ + }}{{\text{O}}_{\text{2}}} \\
  {\text{Cl}}{{\text{O}}^{\text{ \bullet }}}{\text{ + O}} \to {\text{C}}{{\text{l}}^{\text{ \bullet }}}{\text{ + }}{{\text{O}}_{\text{2}}} \\
  {{\text{O}}_{\text{3}}}{\text{ + O}} \to {\text{2}}{{\text{O}}_{\text{2}}} \\
 \]
$$
The depletion of the ozone layer has many effects. It allows the entry of harmful uv radiation into the earth’s atmosphere which is harmful to human life. It causes many types of skin cancer, leukemia, breast cancer in humans.
The UV radiation is also absorbed by the lens and cornea in the eye leading to cataracts.
The incoming of UV rays by ozone layer depletion leads to evaporation from leaves and decreases the soil moisture content.
Inhalation of CFCs can affect the central nervous system and also disturb the heart rhythm leading to death.

Note: Although the uv spectra is a narrow band, yet it causes patches on the skin and destroys the immunological power of the skin. The epidermal layer of human skin has Longherans cells which are the key player in skin immunity. When the uv radiation increased by ozone layer depletion caused by CFCs falls on human skin, the skin breaks down the defence in the skin.