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Carbonic acid is a weak acid with the chemical formula of H2 C O3. It is the reaction product of water and carbon dioxide and exists in an equilibrium with water and carbon dioxide whenever the latter is dissolved in the former, for instance in soda water or blood. It is usually not possible to obtain pure hydrogen bicarbonate as the presence of even a single molecule of water causes the carbonic acid to revert to carbon dioxide and water fairly quickly. However, pure carbonic acid has been found to be quite stable in the absence of water.
In solution, carbonic acid can lose one or two protons. Removing the first proton from carbonic acid forms the bicarbonate ion; removing the second proton leads to the carbonate ion.
- H2CO3 → HCO3- + H+ (pKd = 6.35)
- HCO3- → CO32- + H+ (pKd = 10.33)
When carbonic acid is combined with positive or basic atoms or radicals, salts called carbonates or bicarbonates can form. For instance, combined with lime ( calcium oxideProperties General Name Calcium oxide Chemical formula Ca O Appearance White solid Physical Formula weight 56. 1 amu Melting point 3200 K (2927 °C) Boiling point 3773 K (3500 °C) Density 3. 3 ×103 kg/ m3 Crystal structure NaCl Solubility hydrolysed Thermo) it constitutes marbleThis page is about the metamorphic rock. For the game with little glass spheres see marbles. Marble is metamorphosed limestone, composed of fairly pure calcite (a crystalline form of calcium carbonate, Ca C O). It is extensively used for sculpture, as an and chalkChalk is a soft, white, porous form of limestone composed of the mineral calcium carbonate. It is relatively resistant to erosion and slumping compared to the clays that it is usually associated with, and so forms tall steep cliffs where chalk ridges meet ( calcium carbonateProperties General Name Calcium carbonate Chemical formula Ca CO Appearance White solid Physical Formula weight 100. 1 amu Melting point Liquifies under high pressure at 1612 K (1339 °C) Boiling point decomposes at 1172 K (899 °C) Density 2. 7 ×103 kg/ m3).
Carbonic acid is present in carbonated soft drinks. In more diluted form it plays a major part in cave formation.
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