How does carbon dioxide change the acid-base condition of a solution?

1 Answer
May 2, 2015

The presence of carbon dioxide will increase a solution's acidity because of the formation of carbonic acid.

When carbon dioxide dissolves in aqueous solution, it reacts with water to form carbonic acid, #H_2CO_3#, a weak acid.

http://s1109.photobucket.com/user/csoeder/media/acidification/carbonates.png.html

#CO_(2(g)) rightleftharpoons CO_(2(aq))#

and

#CO_(2(aq)) + H_2O_((l)) rightleftharpoons H_2CO_(3(aq))#

The carbonate acid will then release either one or both of its protons, producing bicarbonate, #HCO_3^(-)#, and carbonate, #CO_3^(-)#, ions, at the same time increasing the concentration of hydronium ions and making the solution more acidic.

#H_2CO_(3(aq)) + H_2O rightleftharpoons HCO_(3(aq))^(-) + H_3O_((aq))^(+)#

#HCO_(3(aq))^(-) + H_2O_((l)) rightleftharpoons CO_(3(aq))^(2-) + H_3O_((aq))^(+)#

http://s1109.photobucket.com/user/csoeder/media/acidification/carbonates.png.html

This is essentially the process responsible for ocean acidification.

Read more on that here:

http://www.pmel.noaa.gov/co2/story/Ocean+Acidification