JEE PYQ: Environmental Chemistry Question 12
Question 12 - 2020 (02 Sep Shift 1)
The statement that is not true about ozone is:
(1) in the stratosphere, CFCs release chlorine free radicals (Cl) which reacts with $\text{O}_3$ to give chlorine dioxide radicals.
(2) in the atmosphere, it is depleted by CFCs.
(3) in the stratosphere, it forms a protective shield against UV radiation.
(4) it is a toxic gas and its reaction with NO gives $\text{NO}_2$.
Show Answer
Answer: (2)
Solution
In presence of sunlight CFC’s molecule divides and release chlorine free radical, which react with ozone give chlorine monoxide radical (ClO$^\cdot$) and oxygen.
$\text{CF}_2\text{Cl}_2(\text{g}) \xrightarrow{\text{UV}} \dot{\text{Cl}}(\text{g}) + \dot{\text{C}}\text{F}_2\text{Cl}(\text{g})$
$\text{Cl}^\cdot(\text{g}) + \text{O}_3(\text{g}) \longrightarrow \text{ClO}^\cdot(\text{g}) + \text{O}_2(\text{g})$
$\text{ClO}^\cdot(\text{g}) + \text{O}(\text{g}) \longrightarrow \text{Cl}^\cdot(\text{g}) + \text{O}_2(\text{g})$
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