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

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, ${H}_{2} C {O}_{3}$, a weak acid.

$C {O}_{2 \left(g\right)} r i g h t \le f t h a r p \infty n s C {O}_{2 \left(a q\right)}$

and

$C {O}_{2 \left(a q\right)} + {H}_{2} {O}_{\left(l\right)} r i g h t \le f t h a r p \infty n s {H}_{2} C {O}_{3 \left(a q\right)}$

The carbonate acid will then release either one or both of its protons, producing bicarbonate, $H C {O}_{3}^{-}$, and carbonate, $C {O}_{3}^{-}$, ions, at the same time increasing the concentration of hydronium ions and making the solution more acidic.

${H}_{2} C {O}_{3 \left(a q\right)} + {H}_{2} O r i g h t \le f t h a r p \infty n s H C {O}_{3 \left(a q\right)}^{-} + {H}_{3} {O}_{\left(a q\right)}^{+}$

$H C {O}_{3 \left(a q\right)}^{-} + {H}_{2} {O}_{\left(l\right)} r i g h t \le f t h a r p \infty n s C {O}_{3 \left(a q\right)}^{2 -} + {H}_{3} {O}_{\left(a q\right)}^{+}$

This is essentially the process responsible for ocean acidification.