One chlorine atom can destroy how many ozone molecules?

• A. 1,000
• B. 10,000
• C. 100,000
• D. 1,000,000

Answer: (C)

Chlorine acts as a catalyst in a cycle that continuously destroys ozone. A chlorine atom reacts with ozone to form chlorine monoxide and oxygen. Then chlorine monoxide reacts with a free oxygen atom to regenerate the chlorine atom and produce another molecule of oxygen. Because the chlorine atom is regenerated, it can keep destroying ozone many times over before it becomes tied up in reservoir forms and is removed from the cycle. Under typical stratospheric conditions, a single chlorine atom can destroy on the order of about 100,000 ozone molecules before it is deactivated. This large destructive potential is why chlorine released from sources like refrigerants and solvents has such a big impact on ozone. The numbers 1,000 or 10,000 would underestimate the catalytic power, while 1,000,000 would exceed the common range observed in the atmosphere.