Chemistry:Molybdic acid

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Molybdic acid
Other names
Molybdic(VI) acid
3D model (JSmol)
EC Number
  • 231-970-5
Molar mass 161.95 g mol−1 [1]
Appearance white crystals (anhydrous)
yellow crystals (monohydrate)
Density 3.112 g/cm3 (anhydrous)
3.124 g/cm3 (monohydrate)
Melting point 300 °C (572 °F; 573 K)[1]
1510 mg dm−3 Soluble in 10% ammonia 35gm/lt
hexagonal (anhydrous)
monoclinic (monohydrate)
GHS pictograms GHS07: HarmfulGHS08: Health hazard
GHS Signal word Warning
H319, H335, H373
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Infobox references

Molybdic acid refers to hydrated forms of molybdenum trioxide and related species. The monohydrate (MoO3·H2O) and the dihydrate (MoO3·2H2O) are well characterized. They are yellow diamagnetic solids.

Structure of the solids

Portion of one layer of hydrated molybdic acid, MoO3·(H2O)2.

Solid forms of molybdic acid are coordination polymers. The monohydrate MoO3·H2O consists of layers of octahedrally coordinated MoO5·(H2O) units where 4 vertices are shared.[3] The dihydrate (image shown above) has the same layer structure with the "extra" H2O molecule intercalated between the layers.[4]

Structure of molybdic acid in solution

In acidified aqueous solutions of molybdic acid, the complex MoO3(H2O)3 is observed. Once again, molybdenum adopts octahedral molecular geometry, probably with three oxo ligands and three aquo ligands.[5]

The salts of molybdic acid are called molybdates. They arise by adding base to solutions of molybdic acid.


Many molybdenum oxides are used as heterogeneous catalysts, e.g. for oxidations. Molybdic acid and its salts are used to make the Froehde reagent for the presumptive identification of alkaloids.


  1. 1.0 1.1 "Molybdic acid | 7782-91-4". 
  2. "C&L Inventory". 
  3. Wells A.F. (1984) Structural Inorganic Chemistry 5th edition Oxford Science Publications ISBN:0-19-855370-6
  4. Krebs, B. (1972). "Die Kristallstruktur von MoO3(H2O)2". Acta Crystallographica B 28 (7): 2222–2231. doi:10.1107/S0567740872005849. 
  5. Solution structure of molybdic acid from Raman spectroscopy and DFT analysis, Oyerindea O.F., Week C.L., Anbarb A.D., Spiro T.G. Inorganica Chimica Acta, 361, 4, (2008), 1000-1007, doi:10.1016/j.ica.2007.06.025