8.3. Types of Chemical Reactions http://www.ck12.org
2NO+O 2 →2NO 2
Nitrogen dioxide is a toxic gas with a sharp odor. It can irritate the eyes and throat and trigger asthma attacks. It is a
major air pollutant.
FIGURE 8.7
In this photo, the air over Los Angeles,
California is brown with smog.Decomposition Reactions
A decomposition reaction is the reverse of a synthesis reaction. In adecomposition reaction, one reactant breaks
down into two or more products. This can be represented by the general equation:
AB→A+B
Two examples of decomposition reactions are described below. You can see other examples at this URL: http://w
ww.youtube.com/watch?v=dxlWtsFinTM.
Decomposition Example 1
An example of a decomposition reaction is the breakdown of carbonic acid (H 2 CO 3 ) to produce water (H 2 O) and
carbon dioxide (CO 2 ). The equation for this reaction is:
H 2 CO 3 →H 2 O+CO 2
Carbonic acid is synthesized in the reverse reaction. It forms when carbon dioxide dissolves in water. For example,
some of the carbon dioxide in the atmosphere dissolves in the ocean and forms carbonic acid. The amount of carbon
dioxide in the atmosphere has increased over recent decades (seeFigure8.8). As a result, the acidity of ocean water
is also increasing. How do you think this might affect ocean life?