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Why is hydrochloric acid named with the prefix hydro-?
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oxyacid
The structure of phosphorous acid, H3PO3.
In chemical nomenclature, the prefix hydro- is used to identify acids that do not contain oxygen.12
When naming an acid, the system depends on the composition of the anion attached to the hydrogen cation. If the anion does not contain oxygen, the acid is named by adding the prefix hydro- and the suffix -ic to the root of the anion's name. Because hydrochloric acid is formed by dissolving hydrogen chloride (HCl) in water, and its chloride anion lacks oxygen, it follows this naming convention.123