Environmental Protection Agency (EPA) MVAC Certification

How many ozone molecules can one chlorine or bromine radical break down in the stratosphere?

1. 10,000

2. 50,000

3. 100,000

4. 500,000

The correct answer is: 100,000

Chlorine and bromine radicals are highly effective at depleting ozone in the stratosphere due to their ability to catalytically break down ozone molecules. One chlorine or bromine radical can destroy a significant number of ozone molecules because of the nature of the chemical reactions involved. When a chlorine or bromine radical encounters ozone (O3), it breaks apart an ozone molecule into oxygen (O2) and a chlorine or bromine monoxide (ClO or BrO). The chlorine or bromine monoxide can then react with another ozone molecule, regenerating the chlorine or bromine radical and allowing it to continue breaking down more ozone molecules. This cycle can repeat numerous times, leading to a substantial cumulative effect on ozone depletion. Research indicates that one chlorine radical can ultimately destroy around 100,000 ozone molecules before it is removed from the stratosphere or converted into a less reactive form. This significant capacity for ozone destruction is a primary reason behind the concerns related to substances like chlorofluorocarbons (CFCs) and halons that release these radicals. Understanding this process is crucial for comprehending the impacts of ozone-depleting substances and the importance of regulations aimed at reducing their emissions to protect the stratospheric ozone