Chlorous acid

 ( Chlorites ) 

Chlorous acid is an inorganic compound with the formula HClO₂. It is a weak acid. Chlorine has oxidation state +3 in this acid. The pure substance is unstable, disproportionating to hypochlorous acid (Cl oxidation state +1) and chloric acid (Cl oxidation state +5):

2 HClO₂ → HClO + HClO₃

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-known sodium chlorite. This and related salts are sometimes used in the production of chlorine dioxide.

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Preparation HClO₂ can be prepared through reaction of barium or lead chlorite and dilute sulfuric acid:

Ba(ClO₂)₂ + H₂SO₄ → BaSO₄ + 2 HClO₂

Pb(ClO₂)₂ + H₂SO₄ → PbSO₄ + 2 HClO₂

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Stability Chlorous acid is a powerful oxidizing agent, although its tendency to undergo disproportionation counteracts its oxidizing potential.

Chlorine is the only halogen to form an isolable acid of formula HXO₂.Egon Wiberg, Arnold Frederick Holleman (2001) Inorganic Chemistry, Elsevier Fluorine is resistant to oxidation, having a −1 oxidation state even in hypofluorous acid, and is thus unable to form any higher oxoacids; despite the name, fluorite minerals are chemically fluoride compounds. Neither bromous acid nor iodous acid has ever been isolated. A few salts of bromous acid, bromites, are known, but no .

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