Question

How do CFCs affect the concentration of ozone in the stratosphere and contribute to the formation of the ozone hole?

Short answer

CFCs contribute to the formation of the ozone hole by releasing chlorine atoms in the stratosphere, which then catalyze the conversion of ozone into oxygen. These reactions are particularly enhanced in the polar regions leading to the formation of an ozone hole.

Step-by-step solution

Understanding Properties of CFCs

Chlorofluorocarbons (CFCs) are kinds of compounds that contain atoms of carbon, chlorine and fluorine. They are stable and non-reactive in the lower atmosphere, which means they can persist for a long time and be transported to the upper atmosphere (stratosphere) by winds.

Atmospheric Reactions of CFCs

Once they reach the stratosphere, CFCs are broken down by solar radiation or sunlight, resulting in the release of chlorine atoms. The overall reaction can be simplified as: CFCl₃ + UV → CFCl₂ + Cl

Impact on Ozone Layer

The chlorine atom released in the stratosphere has the ability to catalyze the conversion of ozone (O₃) into oxygen (O₂) without being consumed. The simplified form of this process can be represented as: \begin{align*} Cl + O₃ &→ ClO + O₂\ ClO + O &→ Cl + O₂ \end{align*}This means that the same chlorine atom can continue to catalyze the destruction of many more ozone molecules, leading to a decrease in the total amount of ozone in the stratosphere.

Formation of Ozone Hole

The hole in the ozone layer is mainly caused by increased concentrations of CFCs. In winter, the cold temperatures in the polar regions cause CFCs and other ozone-depleting substances to accumulate in the polar vortices. When sunlight returns in the spring, it leads to a massive depletion of the ozone layer, thus leading to the ozone hole.