H3VO4

H3VO4, commonly called orthovanadic acid, is the neutral molecular form of the vanadate system in which vanadium is in the +5 oxidation state. Its formula is H3VO4 and its molar mass is approximately 118 g/mol. In aqueous solution it behaves as a weak triprotic acid and forms several orthovanadate species, including H2VO4−, HVO4^2−, and VO4^3−, depending on pH. At low pH the neutral H3VO4 predominates; as pH increases, the species become progressively deprotonated, ultimately yielding VO4^3− under basic conditions.

Structure: H3VO4 features a tetrahedral VO4 unit with one V=O (vanadyl) group. In the neutral molecule, three oxygens carry protons as hydroxyl groups, while one oxygen is the terminal oxo. This geometry is analogous to orthophosphoric acid H3PO4.

Preparation: H3VO4 can be prepared by acidifying aqueous solutions of sodium orthovanadate Na3VO4 or other vanadate sources. The acid form can subsequently be isolated by standard crystallization or evaporation techniques.

Reactions and applications: Orthovanadate species are used as phosphate analogs in biochemistry and mineral chemistry. Sodium orthovanadate and related salts serve as inhibitors of protein tyrosine phosphatases and other phosphatases in enzyme assays, and H3VO4 provides a source of VO4^3− in experiments requiring a neutral vanadate form. In materials science and catalysis, vanadium(V) oxoanions participate in oxidation chemistry and the synthesis of vanadium-containing materials.

Safety: Vanadium(V) compounds can be toxic and irritating; handle with appropriate protective equipment and follow disposal regulations for toxic metal compounds.

See also: orthovanadate, vanadate, Na3VO4.