Haloalkanes and Haloarenes - Result Question 53
####53. Which of the following is responsible for depletion of the ozone layer in the upper strata of the atmosphere?
[2004]
(a) Polyhalogens
(b) Ferrocene
(c) Fullerenes
(d) Freons
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Solution:
- (d) Chlorofluorocarbons, e.g. $CF_2 Cl_2, CHF_2 Cl_2$, $HCF_2 CHCl_2$. These are non-inflammable, colourless and stable upto $550^{\circ} C$. These are emitted as propellants in aerosol spray, refrigerators, fire fighting reagents etc. They absorb UV-rays in the stratosphere and produce free atomic chlorine which results in decomposition of ozone.
Chlorofluorocarbons are chemically inert and hence do not react with any substance with which they come in contact and therefore, float through the atmosphere and as a result enter the stratosphere.
