Problem 26 - Chemistry: The Central Science

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.

Step-by-Step Solution

Answer

Yes, the substance \(\mathrm{CFBr}_{3}\) would likely be effective in depleting the ozone layer if present in the stratosphere, due to its chemical structure and properties. It shares some properties with known ozone-depleting substances like CFCs and halons, as it contains a reactive halogen (bromine) and can initiate a catalytic cycle in which ozone molecules are converted into oxygen gas.

Step 1: Identify the structure of the compound

First, let's identify the structure of the compound \(\mathrm{CFBr}_{3}\). It has one carbon atom, three fluorine atoms, and one bromine atom. The compound is a halogenated hydrocarbon like CFCs and halons.

Step 2: Analyze the chemical properties of the compound

Now, let's analyze the chemical properties of the compound \(\mathrm{CFBr}_{3}\). Like CFCs, it contains a halogen atom (in this case, bromine) which is highly reactive. Bromine atoms, after being released in the stratosphere, can undergo a series of reactions with ozone which could lead to the depletion of the ozone layer. _Particularly_, the reaction starts when the \(\mathrm{CFBr}_{3}\) molecules absorb ultraviolet light from the sun and dissociate into reactive species, like \(\mathrm{CF}_{3}\) and \(\mathrm{Br}\). After this, the reactive bromine atom can react with an ozone molecule (\(\mathrm{O}_{3}\)), and convert it into oxygen gas (\(\mathrm{O}_{2}\)) through a catalyst cycle: \[1.\: \mathrm{Br} + \mathrm{O}_3 \rightarrow \mathrm{BrO} + \mathrm{O}_2\] \[2.\: \mathrm{BrO} + \mathrm{O} \rightarrow \mathrm{Br} + \mathrm{O}_2\] The net effect of these reactions is the conversion of one ozone molecule and one atomic oxygen into two oxygen gas molecules: \[\mathrm{O}_3 + \mathrm{O} \rightarrow 2 \mathrm{O}_2\] In this process, the bromine atom acts as a catalyst, as it is not consumed in the reaction and can repeatedly participate, thus depleting a significant amount of ozone molecules.

Step 3: Compare with known ozone-depleting substances

When comparing \(\mathrm{CFBr}_{3}\) to known ozone-depleting substances, we observe that it shares some properties with CFCs and halons. Like these compounds, it contains a halogen that is highly reactive and could initiate a catalytic cycle by releasing bromine atoms in the stratosphere, leading to ozone depletion.

Step 4: Conclude whether CFBr3 would be effective in ozone depletion

Based on the chemical structure and reactions involving \(\mathrm{CFBr}_{3}\), we can conclude that, if present in the stratosphere, it would be effective in depleting the ozone layer due to the presence of a reactive halogen (bromine) in its structure and its potential to initiate a catalytic cycle involving ozone molecules.