This type of reaction is called photodissociation—in photodissociation, a bond
is broken as a molecule absorbs a photon of light energy.
In the next step in the production of ozone, elemental oxygen and diatomic
oxygen collide.
O(g)+O 2 (g)→O 3 (g)Atmospheric ozone absorbs solar radiation and decomposes back to elemental
and diatomic oxygen. If ozone didn’t absorb this high-energy radiation, the
damaging rays would reach the planet and destroy much of its plant and animal
life. As you have probably read about or seen in the news, certain chemicals
produced by humans are thought to be responsible for the gradual degradation of
the ozone layer. The primary culprits in ozone layer destruction are
chlorofluorocarbons, which have been created for use as propellants in spray
cans and car air conditioners. Chlorofluorocarbons react with light energy to
form, among other compounds, free chlorine. This chlorine reacts with ozone to
form chlorine monoxide, ClO, and oxygen. The fact that ozone is a reactant in
this chemical reaction means that it is slowly being consumed; Earth’s
atmosphere is slowly being robbed of its protective ozone layer.
The Greenhouse Effect
Another environmental topic that’s hotly debated in the news is the greenhouse
effect. In short, the greenhouse effect refers to the buildup of carbon dioxide,
CO 2 , and other greenhouse gases in the atmosphere. Greenhouse gases are the
result of the combustion of fossil fuels such as coal and oil; they absorb infrared
radiation that reflects off the earth from the sun, effectively trapping it in the
atmosphere and creating an effect much like that in a greenhouse (hence the
name).
Acid Rain
The SAT Chemistry Subject Test might also expect you to know a little
something about what acid rain is and how it’s formed. By definition, acid rain
is rain that has an abnormally low pH due to the presence of certain oxides,
which are pollutants produced by human activities. One of the most prevalent
classes of oxide pollutants is the sulfur oxides, in the form SO 2 . SO 2 is produced
when coal and oil are combusted and can react with either ozone or diatomic