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

Maharashtra BoardEnglish MediumSTD 12 ScienceBIOLOGYBiodiversity, Conservation and Environmental Issues4 Marks
Question
How is ozone hole formed? OR 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 $\text{UV}$ 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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