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| Names | |
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| IUPAC name Chlorous acid, Chloric (III) acid | |
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| Properties | |
| HClO2 | |
| Molar mass | 68.46 g/mol |
| Acidity (pKa) | 1.96 |
| Conjugate base | Chlorite |
Except where otherwise noted, data are given for materials in theirstandard state (at 25 °C [77 °F], 100 kPa). | |
Chlorous acid is aninorganic compound with the formula HClO2. It is aweak acid. Chlorine hasoxidation state +3 in this acid. The pure substance is unstable,disproportionating tohypochlorous acid (Cl oxidation state +1) andchloric acid (Cl oxidation state +5):
Although the acid is difficult to obtain in pure substance, the conjugate base,chlorite, derived from this acid is stable. One example of a salt of this anion is the well-knownsodium chlorite. This and related salts are sometimes used in the production ofchlorine dioxide.
HClO2 can be prepared through reaction of barium or lead chlorite and dilutesulfuric acid:
Chlorous acid is a powerful oxidizing agent, although its tendency to undergo disproportionation counteracts its oxidizing potential.[citation needed]
Chlorine is the onlyhalogen to form an isolable acid of formula HXO2.[1]Fluorine is resistant to oxidation, having a -1 oxidation state even inhypofluorous acid, and is thus unable to form any higher oxoacids; despite the name,fluorite minerals are chemicallyfluoride compounds. Neitherbromous acid noriodous acid has ever been isolated. A few salts ofbromous acid, bromites, are known, but noiodites.[1]
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