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Biodiversity, Conservation and Environmental Issues — BIOLOGY STD 12 Science — Question

Maharashtra BoardEnglish MediumSTD 12 ScienceBIOLOGYBiodiversity, Conservation and Environmental Issues5 Marks
Question
How is ozone hole formed? Give effect of $\text{CFC}$ on ozone shield.
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Answer

  1. The ozone molecules are attacked by chlorofluorocarbon molecules. This action causes disturbances in the ozone shield due to increased rate of ozone degradation by Chlorofluorocarbon $\text{(CFC)}.$
  2. $\text{CFCs}$ can move upwards to reach stratosphere. Here $UV$ rays act on them and release $Cl^–$ atoms. The released $Cl-$degrades ozone, which subsequently releasing molecular oxygen.
  3. $Cl^–$ atoms act as catalyst. So, they remain in the stratosphere and continue the effect of ozone degradation.
  4. This results in ozone depletion. This leads to the formation of ozone hole which is a large area of thinned ozone layer. One such ozone hole was observed over the Antarctic region.

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