MHTCET 5 May 2025 Shift 2 Paper

Concept:Nitrogen oxides, particularly nitric oxide ($\mathrm{NO}$), act as catalysts in the destruction of stratospheric ozone.Explanation:The ozone layer in the upper atmosphere is depleted by nitrogen oxides emitted from the exhaust systems of cars and supersonic jet aeroplanes.Nitric oxide ($\mathrm{NO}$) is the main oxide of nitrogen responsible for this depletion.It destroys ozone through a catalytic cycle:Step 1: $\mathrm{NO} + \mathrm{O}_3 \rightarrow \mathrm{NO}_2 + \mathrm{O}_2$Step 2: $\mathrm{NO}_2 + \mathrm{O} \rightarrow \mathrm{NO} + \mathrm{O}_2$In this cycle, $\mathrm{NO}$ is regenerated, so a single molecule of $\mathrm{NO}$ can destroy many ozone molecules continuously.Other nitrogen oxides like $\mathrm{NO}_2$, $\mathrm{N}_2\mathrm{O}$, and $\mathrm{N}_2\mathrm{O}_5$ are not the primary species directly released that initiate this depletion.Therefore, the gas causing ozone layer depletion is nitric oxide.Answer:$\mathrm{NO}$ (Option A)