Question

1. In the stratospheric level of the atmosphere there is a high level of ozone, O₃. This ozone absorbs much of the ultraviolet light from the sun and thus protects life in the surface of the Earth from harmful high level of ultraviolet radiation. Explain why one chlorofluorocarbon (CFC) molecule in the ozone layer is capable of breaking down hundreds and even thousands of ozone molecules?

Answer 1

CFCs, composed by chlorine, fluorine, and carbon, have a long lifecycle, which favours their accumulation. CFCs do not easily react with other substances. In fact, they break up only through sunlight, which divides their molecules, causing the release of chlorine (Cl). Once the chlorine is released, it is able to react with ozone (O3), to form chlorine monoxide (ClO) and oxygen (O2).

Cl + O3 = ClO + O2

When the molecule of chlorine monoxide (ClO) meets another molecule of oxygen (O) it breaks up, releasing chlorine (Cl), which can “destroy” another molecule of ozone (O3), creating the catalytic cycle of chlorine.

ClO + O = Cl + O2