Once a single chlorine atom has been freed in the stratosphere, what happens to it as it reacts with ozone molecules?
- AIt is consumed after destroying one ozone molecule and then settles back toward the ground
If chlorine were consumed one for one, the total damage would be limited to the number of chlorine atoms released, which is not what is observed in the stratosphere.
- BIt bonds permanently to the first ozone molecule it meets and stops reacting after that
Chlorine monoxide is only a temporary product. It reacts again and hands the chlorine atom back in its original form, so no permanent bond ends the cycle.
- It is regenerated after each reaction and goes on to destroy many thousands of ozone molecules
- DIt is neutralized by sunlight within a few minutes before it can reach any ozone
Sunlight is what frees the chlorine atom in the first place, so ultraviolet light starts the process rather than shutting it down.
Why C is correct
The reaction chain returns the chlorine atom to its original form each time around, so it is never used up by the ozone it destroys. That catalytic recycling is the reason a small mass of refrigerant can do damage far out of proportion to the amount released.
What this question is testing
Checks whether the candidate understands ozone destruction as a repeating catalytic chain rather than a simple one to one reaction, which is the conceptual base for the whole ozone section of the Core exam.
On the job
This is the answer you give when a customer or a helper argues that a couple of ounces lost off a hose cannot possibly matter. The catalytic cycle is the reason recovery equipment, certification, and the venting ban all exist for quantities a technician might consider trivial. It also explains why the industry moved to molecules with no chlorine at all rather than simply handling chlorine based refrigerants more carefully.
Memory technique
Think of chlorine as a wrecking ball on a crane, not a bullet. The bullet stops after one hit; the wrecking ball swings back for the next wall.
Exam tip
Watch for answer choices that describe chlorine being used up or permanently bound. The exam wants the idea that one atom keeps working over and over.
Where to look it up
Remember the phrase catalytic chain reaction: one chlorine atom, many thousands of ozone molecules.