Select the compound that is primarily implicated in ozone layer depletion. A) H₂O, B) CCl₄, C) KNO₃, D) NO₂, or E) CO₂.
H₂O is the chemical symbol for water. CCl₄ is the symbol for carbon tetrachloride. KNO₃ is the symbol for potassium nitrate. NO₂ is the symbol for nitrogen dioxide. And CO₂ is the symbol for carbon dioxide. Ozone layer depletion is one of the many major environmental issues that have come to light within the last 100 years. Ozone is an allotrope of oxygen, having the chemical symbol O₃. Ozone molecules in the upper atmosphere protect us from ultraviolet rays, intercepting and neutralizing them. Ozone is generated through bombardment of cosmic rays on the atmosphere and through lightning strikes and other processes.
The primary threat to the ozone layer produced by humans are CFCs, chlorofluorocarbons. Chlorofluorocarbons and similar related compounds generate reactive radicals in the upper atmosphere. These radicals can act as catalysts for the breakdown of ozone, rapidly interacting, decomposing ozone, and being regenerated again and again. Our job is to look at each compound in turn and identify whether it’s been associated with ozone layer depletion.
Water makes up a high proportion of the atmosphere itself. So we would be a great risk if it were associated with ozone layer depletion. As it is, H₂O is very stable and does not react with the ozone. Carbon tetrachloride, on the other hand, has lots of chlorines. It’s an example of a chlorocarbon. While not quite in the same family as chlorofluorocarbons, it has the same result when released into the atmosphere. Bombardment by ultraviolet light from the sun generates those dangerous chlorine radicals. These radicals and many others produced inside reactions help to break down ozone, depleting the ozone layer. So carbon tetrachloride is well known to pose a hazard to the ozone layer. However, let’s have a look at the others just in case.
Potassium nitrate is an ionic solid. If it were to dissolve in water on water were to be released into the atmosphere, the potassium nitrate will be left behind. So the potassium nitrate doesn’t have a route to get up to the ozone layer in the first place. Nitrogen dioxide does not produce the radicals that will be involved in the degradation of ozone. So nitrogen dioxide is not associated with ozone layer depletion. It is, however, an acidic gas. So it does form nitric acid and induce acid rain. It’s a similar story for carbon dioxide. Carbon dioxide does not react directly with ozone. So it’s not responsible for depleting the ozone layer. Carbon dioxide is, however, a greenhouse gas and because of the levels in the atmosphere does pose a significant risk to Earth’s ecosystem.
However, the question is about the ozone layer and its depletion. And the compound that’s primarily implicated in ozone layer depletion out of this list is CCl₄.