Question

(a) Why is the fluorine present in chlorofluorocarbons not a major contributor to depletion of the ozone layer? (b) What are the chemical forms in which chlorine exists in the stratosphere following cleavage of the carbonchlorine bond?

Short answer

(a) Fluorine in CFCs does not contribute majorly to ozone layer depletion because it forms stable compounds in the stratosphere, preventing it from reacting with ozone. The carbon-fluorine bond is stronger and less reactive than the carbon-chlorine bond, making fluorine less likely to participate in destructive reactions with ozone. (b) After the cleavage of the carbon-chlorine bond in CFCs, the chemical forms of chlorine in the stratosphere are the reactive chlorine atom (Cl) and chlorine monoxide (ClO). These species participate in a reaction cycle responsible for the depletion of ozone.

Step-by-step solution

(a) The role of fluorine in chlorofluorocarbons (CFCs) and its contribution to ozone layer depletion

: Fluorine in CFCs does not contribute majorly to the ozone layer depletion primarily because it forms stable compounds with other elements in the stratosphere, which prevents it from reacting with ozone. When CFCs are broken down by ultraviolet (UV) radiation in the stratosphere, the carbon-fluorine bond is relatively stronger and less reactive than the carbon-chlorine bond, which makes it less likely to participate in destructive reactions with ozone. This means that fluorine is not a significant contributor to depletion of the ozone layer.

(b) Chemical forms of chlorine in the stratosphere after the cleavage of carbon-chlorine bond

: When the carbon-chlorine bond in CFCs is broken in the stratosphere by UV radiation, it forms reactive chlorine atoms (Cl). Reactive chlorine atoms can participate in the following reactions: 1. Chlorine atoms react with ozone to form chlorine monoxide (ClO) and molecular oxygen (O2): \[ Cl + O_3 \rightarrow ClO + O_2 \] 2. Chlorine monoxide (ClO) can further react with atomic oxygen (O) to create molecular oxygen (O2) and regenerate the chlorine atom (Cl): \[ ClO + O \rightarrow Cl + O_2 \] This cycle of reactions involving chlorine species is responsible for the depletion of ozone. So, after the cleavage of the carbon-chlorine bond, the chemical forms of chlorine in the stratosphere are the reactive chlorine atom (Cl) and chlorine monoxide (ClO).