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| Names | |
|---|---|
| IUPAC name Sulfurous acid | |
| Identifiers | |
| CAS Number | |
| 3D model (JSmol) | |
| ChEBI | |
| ChEMBL | |
| ChemSpider | |
| ECHA InfoCard | 100.029.066 
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| KEGG | |
| PubChem CID | |
| UNII | |
| CompTox Dashboard (EPA) | |
InChI
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SMILES
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| Properties | |
| Chemical formula | H2SO3 |
| Molar mass | 82.07 g/mol |
| Acidity (pKa) | 1.857, 7.172 |
| Hazards | |
| Flash point | Non-flammable |
| Related compounds | |
Except where otherwise noted, data are given for materials in their standard state (at 25 °C , 100 kPa).
 N verify (what is ?)
Infobox references
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Sulfurous acid (British English: sulphurous acid) is the chemical compound with the formula H2SO3. There is no evidence that sulfurous acid exists in solution, but the molecule has been detected in the gas phase. The conjugate bases of this elusive acid are, however, common anions, bisulfite (or hydrogensulfite) and sulfite.
Raman spectra of solutions of sulfur dioxide in water show only signals due to the SO2 molecule and the bisulfite ion, HSO3. The intensities of the signals are consistent with the following equilibrium:
- SO2 + H2O ⇌ HSO3 + H
- Ka = 1.54×10; pKa = 1.81.
- SO2 + H2O ⇌ HSO3 + H
Aqueous solutions of sulfur dioxide, which sometimes are referred to as sulfurous acid are used as reducing agents and as disinfectants, as are solutions of bisulfite and sulfite salts. They are also mild bleaches, and are used for materials which may be damaged by chlorine-containing bleaches.
References
- D. Sülzle, M. Verhoeven, J. K. Terlouw, H. Schwarz (1988). "Generation and Characterization of Sulfurous Acid (H2SO3) and of Its Radical Cation as Stable Species in the Gas Phase". Angew. Chem. Int. Ed. Engl. 27 (11): 1533–4. doi:10.1002/anie.198815331.
{{cite journal}}: CS1 maint: multiple names: authors list (link) - Jolly, William L. (1991). Modern Inorganic Chemistry (2nd ed.). New York: McGraw-Hill. ISBN 0-07-032768-8.