# Carbonic acid, bicarbonate in water [closed]

When you add CO2 into water, carbonic acid is created. From carbonic acid (H2CO3), HCO3 + H is formed. When CO2, and H2CO3 leave the water, does HCO3 leave as well, often measure as kH, carbonate hardness?

## closed as unclear what you're asking by Todd Minehardt, airhuff, Jon Custer, Karsten Theis, MithoronApr 18 at 18:50

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The chemistry is a bit more complicated than you have described. When $$\ce{CO2}$$ dissolves in water, most of the carbon species are dissolved $$\ce{CO2}$$. Carbonic acid, the bicarbonate anion and the carbonate anion are minor carbon species. (See the Wikipedia article - Carbonic Acid.)
You can remove the $$\ce{CO2}$$ by boiling the water, or by sparging (blowing bubbles of a gas containing no $$\ce{CO2}$$ in the water). But it is only $$\ce{CO2}$$ that will leave the solution. The equilibriums with carbonic acid, bicarbonate, and carbonate all shift of course as $$\ce{CO2}$$ is removed.