Model Answer
0 min readIntroduction
The ozone layer, a region of Earth’s stratosphere, absorbs most of the Sun’s harmful ultraviolet (UV) radiation. Its depletion poses significant risks to life on Earth, including increased skin cancer rates and damage to ecosystems. Chlorofluorocarbons (CFCs), once widely used in refrigerants and aerosols, are major contributors to ozone depletion. These stable compounds, however, undergo a complex degradation process in the stratosphere, releasing chlorine atoms that catalytically destroy ozone molecules.
Mechanism of Ozone Degradation by CFCs
The degradation process unfolds in several steps:
- CFC Release & Transport: CFCs are released into the atmosphere and, due to their stability, slowly migrate to the stratosphere.
- UV Radiation Breakdown: In the stratosphere, high-energy UV radiation breaks down CFCs, releasing chlorine atoms (Cl). Cl + CFC → Cl + other products
- Catalytic Ozone Destruction: Chlorine atoms act as catalysts in a chain reaction:
- Cl + O3 → ClO + O2 (Chlorine reacts with ozone, forming chlorine monoxide and oxygen)
- ClO + O → Cl + O2 (Chlorine monoxide reacts with a single oxygen atom, regenerating chlorine and forming oxygen)
- Chain Reaction: The regenerated chlorine atom can then destroy another ozone molecule, repeating the cycle. A single chlorine atom can destroy thousands of ozone molecules.
This catalytic cycle continues until the chlorine atom is removed by reacting with other molecules, such as methane. Bromine atoms from halons also participate in a similar ozone-depleting process.
Conclusion
In conclusion, CFCs initiate a catalytic chain reaction in the stratosphere, leading to the destruction of ozone molecules. The release of chlorine atoms, triggered by UV radiation, is central to this process. International efforts, like the Montreal Protocol, have aimed to phase out CFCs to mitigate ozone depletion and protect the Earth from harmful UV radiation. Continued monitoring and adherence to these protocols are vital for ozone layer recovery.
Answer Length
This is a comprehensive model answer for learning purposes and may exceed the word limit. In the exam, always adhere to the prescribed word count.