Ozone layer chemistry: approximately how many ozone molecules can a single chlorine atom released from a CFC catalytically destroy before it is deactivated in the stratosphere?

Introduction / Context:
Chlorofluorocarbons (CFCs) release chlorine radicals in the stratosphere under UV radiation. These radicals catalyze ozone destruction through chain reactions, thinning the protective ozone layer and increasing UV-B at the surface.

Given Data / Assumptions:

• Steady catalytic cycles in sunlit stratosphere.
• Chlorine radical persists through multiple reaction cycles.
• Order-of-magnitude estimate requested.

Concept / Approach:
A single chlorine atom can participate repeatedly in catalytic cycles such as: Cl + O3 -> ClO + O2; ClO + O -> Cl + O2. Because the chlorine atom is regenerated, it can destroy many ozone molecules before being sequestered (e.g., into reservoirs like HCl or ClONO2).

Step-by-Step Solution:

Verification / Alternative check:
Educational references and atmospheric models frequently cite a chain length on the order of one hundred thousand, aligning with observed polar ozone depletion episodes before Montreal Protocol controls.

Why Other Options Are Wrong:

• 10^2 or 10^1: far too low for catalytic chain processes.
• 10^9 or 10^15: unrealistically high given termination reactions and reservoir species formation.

Common Pitfalls:
Assuming radicals act stoichiometrically; ignoring reservoir species that eventually remove active chlorine from the cycle.

Final Answer:
10^5 (about one hundred thousand)