Question

Would you expect the substance \(\mathrm{CFBr}_{3}\) to be effective in depleting the ozone layer, assuming that it is present in the stratosphere? Explain.

Short answer

Yes, we would expect the compound \(\mathrm{CFBr}_{3}\) to be effective in depleting the ozone layer if it was present in the stratosphere. The compound can undergo dissociation when exposed to high-energy UV radiation, leading to the release of reactive bromine atoms, which are highly effective in catalyzing ozone depletion reactions. Bromine atoms can destroy up to 100 times more ozone molecules than chlorine atoms due to their higher reactivity and the lower concentration of natural bromine sinks in the stratosphere.

Step-by-step solution

Understand ozone depletion mechanism

Ozone depletion in the stratosphere is mainly caused by the presence of certain reactive compounds, such as chlorine and bromine, which can catalyze the conversion of ozone (\(\mathrm{O}_{3}\)) back into molecular oxygen (\(\mathrm{O}_{2}\)). The most well-known example of a chlorine-containing compound that depletes the ozone layer is chlorofluorocarbon (CFC). These compounds release chlorine atoms in the stratosphere through UV light dissociation, which in turn lead to ozone depletion via a chain reaction. Similarly, bromine-containing compounds, called halons, can also contribute to ozone depletion. Both chlorine and bromine are halogens, so we need to evaluate if the compound \(\mathrm{CFBr}_{3}\) can undergo similar reactions in the stratosphere.

Examine the stability of \(\mathrm{CFBr}_{3}\) in the stratosphere

In the stratosphere, the compound \(\mathrm{CFBr}_{3}\) would be exposed to high-energy UV radiation. This exposure can lead to the dissociation of \(\mathrm{CFBr}_{3}\), breaking one or more of the carbon-bromine (C-Br) bonds and releasing reactive bromine atoms. Bromine atoms are known to be highly effective in catalyzing ozone depletion reactions. Reactive bromine atoms can lead to destruction of ozone via the following chain reaction: 1. Bromine atom reacts with ozone: \(\mathrm{Br} + \mathrm{O}_{3} \rightarrow \mathrm{BrO} + \mathrm{O}_{2}\) 2. Bromine monoxide reacts with ozone: \(\mathrm{BrO} + \mathrm{O} \rightarrow \mathrm{Br} + \mathrm{O}_{2}\) The released bromine atom can then react with other ozone molecules, leading to a continuous chain reaction and significant ozone depletion.

Compare the reactivity of chlorine and bromine in ozone depletion

Bromine atoms are significantly more effective at depleting the ozone layer than chlorine atoms. One bromine atom can destroy up to 100 times more ozone molecules than one chlorine atom. This is due to the higher reactivity of bromine compared to chlorine, the lower concentration of natural bromine sinks in the stratosphere, and the fact that BrO-Br catalytic cycles dominate BrO-Cl catalytic cycles. Considering the efficiency of bromine in ozone depletion reactions and the ability of the given compound \(\mathrm{CFBr}_{3}\) to release reactive bromine atoms when exposed to high-energy UV radiation in the stratosphere, we can expect \(\mathrm{CFBr}_{3}\) to be effective in depleting the ozone layer if it was present in the stratosphere.