Video Transcript
Which of the following is a
balanced reaction equation for the formation of ozone? (A) O3 reacts to produce O plus
O2. (B) O2 reacts to produce O3. (C) O2 reacts to produce two O3
plus O. (D) O plus O2 react to produce
O3. (E) Two O3 reacts to produce three
O3.
Ozone is a trace gas with the
chemical formula O3. So, it is composed of three oxygen
atoms bonded together. Ozone is produced naturally in the
stratosphere layer of the atmosphere, about 20 to 40 kilometers above the Earth’s
surface. Relatively high concentrations of
ozone gas molecules there form a layer called the ozone layer. This layer is vital for life on
Earth as ozone absorbs harmful wavelengths of ultraviolet radiation coming from the
Sun.
Now, we said ozone is produced
naturally in the atmosphere. And the question asks us to select
the reaction equation for this process. This is how ozone forms. The energy from UV radiation
reaching the stratosphere is absorbed by some oxygen gas molecules there. This causes the molecules to split
apart. Highly reactive free atoms of
oxygen are produced. These energetic particles move
apart from each other. Then the free oxygen atoms, also
called free radicals, collide with other oxygen gas molecules. Finally, new ozone gas molecules
are produced.
We can write this process in two
simplified steps in the form of chemical equations. First, oxygen gas breaks apart
under UV radiation to form two oxygen gas atoms. We write this as O2 gas reacts to
form two O gas. Then, an oxygen atom reacts with an
oxygen molecule forming ozone. We write this as O gas plus O2 gas
reacts to form O3 gas. Now, both of these reactions are
necessary for the formation of ozone. However, it is the second reaction,
specifically, in which ozone gas molecules are actually formed.
We can see that answer option (D)
has the same reaction equation as the one we wrote. So, finally, the balanced reaction
equation for the formation of ozone is answer (D): O plus O2 react to form O3.
