Environmental Chemistry - Result Question 30
8. Assertion (A) Ozone is destroyed by CFCs in the upper stratosphere.
Reason (R) Ozone holes increase the amount of UV radiation reaching the earth.
(2019 Main, 8 April I)
(a) Assertion and Reason are incorrect.
(b) Assertion and Reason are both correct and the Reason is the correct explanation for the Assertion.
(c) Assertion and Reason are correct, but the Reason is not the explanation for the Assertion.
(d) Assertion is false, but the Reason is correct.
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Answer:
Correct Answer: 8. (a)
Solution:
- Ozone is destroyed by CFCs in the upper stratosphere. These compounds ultimately reach the stratosphere where they get broken down by powerful UV radiations and release chlorine free radical. The chlorine free radicals react with ozone and cause its depletion by converting it into chlorine monoxide radical and molecular oxygen.
$$ \begin{array}{r} CF _2 Cl _2(g) \stackrel{h v}{\longrightarrow} Cl(g)+\dot{CF _2 Cl(g)} \ CFCl _3(g) \stackrel{h v}{\longrightarrow} CFCl _2(g)+\dot{Cl}(g) \ \dot{Cl}(g)+O _3(g) \longrightarrow Cl \dot{O}(g)+O _2(g) \end{array} $$
Ozone holes increase the amount of UV radiation reaching the earth. These radiations can cause skin cancer, sunburns, ageing of skin.
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