Acid rain causes an increase in the pH (a measure of acidity) in bodies of water. It has been proposed that calcium carbonate, a source of the carbonate ( ion and a common inexpensive chemical, could be used to treat the effects of acid rain via the following reaction:

Write down the equilibrium expression that exists between carbonic acid (), the hydrogen ion and the carbonate anion. Carbonic acid is an unstable molecule and easily decomposes into carbon dioxide and water. How might this approach be used to reduce the effects of acid rain?