Which of the following statements about the depletion of ozone layer is correct?
(a) The problem of ozone depletion is less serious at poles because NO2 solidifies and is not available for consuming CIO· radicals.
(b) The problem of ozone depletion is more serious at poles because ice crystals in the clouds over poles act as catalyst for photochemical reactions involving the decomposition of ozone of Cl· and CIO· radicals.
(c) Freons, chlorofluorocarbons, are inert. Chemically, they do not react with ozone in stratosphere.
(d) Oxides of nitrogen also do not react with ozone in stratosphere.
Correct answer: (c) Freons, chlorofluorocarbons, are inert. Chemically, they do not react with ozone in stratosphere.
Explanation:
Freons and chlorofluorocarbon find their way to stratosphere through without being destroyed in the troposphere due to their low reactivity. In the stratosphere the Cl and Br atoms are liberated from the parent compounds by the action of ultraviolet light
e.g.
CF2Cl2 + hv → CF2Cl + Cl
CFCl3 + hv → CFCl2 + Cl
The Cl atoms can destroy ozone molecules through a variety of catalytic cycles.