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EEJ MAIN Chemistry QUESTION #5523
Question 1
Identify the reaction that is NOT part of the ozone layer depletion mechanism in the stratosphere.
  • $CF_2Cl_2(g) \xrightarrow{hv} \cdot Cl(g) + \cdot CF_2Cl(g)$
  • $Cl\dot{O}(g) + O(g) \rightarrow \cdot Cl(g) + O_2(g)$
  • $CH_4 + 2O_3 \rightarrow 3\,CH_2{=}O + 3H_2O$✔️
  • $HOCl(g) \xrightarrow{hv} \cdot OH(g) + \cdot Cl(g)$
Correct Answer Explanation
The ozone depletion cycle involves: (A) CFCs releasing Cl radicals under UV, (B) ClO reacting with O atom to regenerate Cl radical (chain propagation), (D) HOCl photolysis to give OH and Cl radicals — all are real steps. Option (C), the reaction of $CH_4$ with $O_3$ to give formaldehyde and water, is NOT a recognized step in stratospheric ozone depletion chemistry.