Question

Ozone layer is depleted by _______.

• A. \( \text{NO} \)
• B. \( \text{NO}_2 \)
• C. \( \text{NO}_3 \)
• D. \( \text{N}_2\text{O}_5 \)

Hint:

Remember that ozone depletion involves \textbf{catalytic cycles}. The active species (like Cl\(\cdot\) or NO) is regenerated, which is why a small amount can cause significant damage to the ozone layer.

Answer 1

The Correct Option is A

Step 1: Recall the mechanism of ozone depletion. The ozone layer is depleted by free radical catalysts. The most well-known are chlorine radicals (from CFCs) and nitric oxide radicals.
Step 2: Analyze the role of nitric oxide (NO). Nitric oxide, often produced by the exhaust of supersonic jets in the stratosphere, acts as a catalyst in a cycle that converts ozone (\(O_3\)) to oxygen (\(O_2\)). The catalytic cycle is as follows: \[ \text{NO}(g) + \text{O}_3(g) \rightarrow \text{NO}_2(g) + \text{O}_2(g) \] \[ \text{NO}_2(g) + \text{O}(g) \rightarrow \text{NO}(g) + \text{O}_2(g) \] The NO molecule is regenerated in the second step, allowing it to destroy thousands more ozone molecules.