Carbonic acid

From Sciencemadness Wiki
Jump to: navigation, search
Carbonic acid
Carbonic acid.jpg
Solution of carbon dioxide in water
IUPAC name
Carbonic acid
Other names
Acid of air
Aerial acid
Carbon dioxide solution
Dihydrogen carbonate
Hydroxymethanoic acid
Molar mass 62.03 g/mol
Appearance White solid/colorless gas (pure compound)
Unstable liquid (aq. solution)
Odor Odorless
Density 1.668 g/cm3
Melting point Decomposes
Boiling point Decomposes
Only stable in solution
Solubility Soluble in glycerol
Insoluble in ethanol
Acidity (pKa) 3.6 (pKa1 for H2CO3 only)
6.3 (pKa1 including CO2(aq))
10.32 (pKa2)
Safety data sheet FisherScientific (aq. sol.)
Flash point Non-flammable
Related compounds
Related compounds
Dimethyl carbonate
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Infobox references

Carbonic acid is a very unstable, weak acid formed in small concentrations with dissolution of its anhydride, carbon dioxide, in water. Any solution containing it also contains molecular carbon dioxide dissolved in water.



Anhydrous carbonic acid cannot be isolated under normal conditions. Only in extreme conditions it becomes stable and isolable in the form of a white solid (below 220 K) or a colorless gas (above 220 K); when transferred to normal conditions, it remains stable in absence of water vapor but decomposes rapidly on contact with it[1]. Solutions of carbonic acid typically resemble soda water or mineral water (and usually are soda water or mineral water).


Carbonic acid is a weak diprotic acid. Its first dissociation gives H+ and the hydrocarbonate anion, HCO3-. The second dissociation gives another H+ and the carbonate anion, CO32-.

Solutions of carbonic acid and carbon dioxide react with alkaline bases, forming carbonate salts.

Sources and production

Solutions of carbon dioxide containing carbonic acid are sold as carbonated water.

Such a solution can also be made by reacting any carbonate salt with any acid stronger than carbonic acid. It can also be made from water and carbon dioxide using a soda siphon or carbonator.




Solutions of carbonic acid are absolutely safe. They can be consumed by humans with no ill effects, providing no other chemicals are present in the solution. They are well known for the peculiar taste and refreshing effect provided by bubbles of carbon dioxide.


Solutions of carbonic acid can be stored in closed plastic bottles. You know, the same way you store soda. Because they are soda.


Carbonic acid does not require any special disposal and can be poured down the drain.



Relevant Sciencemadness threads