The catalytic destruction of ozone by chlorine radicals in the stratosphere can be modeled by the following elementary steps:
Step 1 Cl• + O₃ → ClO• + O₂ fast
Step 2 ClO• + O → Cl• + O₂ slow
Atomic oxygen, O(g), is continually produced photochemically from O₃ decomposition, so its concentration can be treated as approximately constant over short time intervals.
(a) Combine the two elementary steps to verify the net reaction for catalytic ozone destruction.
(b) Identify the species that acts as a catalyst and the species that acts as an intermediate. Justify each classification in terms of consumption and regeneration patterns in the steps above.
(c) Explain why continuous input of atomic oxygen is necessary for the catalytic cycle to proceed, even though atomic oxygen is not itself the catalyst.
(d) Suppose the atmospheric concentration of Cl• doubles while [O₃] and [O] remain unchanged. Using the slow-step approximation, predict the qualitative effect on the overall rate of ozone destruction and justify your reasoning.