An oxoacid is an acid which contains oxygen. More specifically, it is an acid which

1. contains oxygen;
2. contains at least one other element;
3. has a least one hydrogen atom bound to oxygen; and
4. forms an anion by the loss of one or more protons.

The name oxyacid is sometimes used, although this is not recommended.

Under Lavoisier's original theory, all acids contained oxygen, which was named from the Greek οξυς (oxys) (acid, sharp) and γεινομαι (geinomai) (engender). It was later discovered that some acids, notably hydrochloric acid, did not contain oxygen and so a distinction was made for those that did.

Common oxoacids include:

• Sulfuric acid
• Nitric acid
• Phosphoric acid

Common acids which are not oxoacids include:

• Hydrochloric acid
• Hydrofluoric acid

Although carboxylic acids fulfil the criteria above, they are not generally considered as oxoacids.

Note

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1. This final criteria has the effect of excluding boric acid from the strict definition, as it forms its anion by addition of hydroxide rather than loss of a proton: B(OH)₃ + H₂O  ^*− + H⁺. However, boric acid is usually considered to be an oxoacid nonetheless.

External link

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• IUPAC definition of "oxoacid" (from the "Gold Book")

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