Molybdic acid

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Molybdic acid
MoO3aq2Layering.png
Names
Other names
Molybdic(VI) acid
Identifiers
3D model (Jmol)
ChemSpider
ECHA InfoCard 100.029.063
EC Number 231-970-5
Properties
MoO3·H2O
Molar mass 161.95 g mol−1 [1]
Density 3.1 g cm−3 [1]
Melting point 300 °C (572 °F; 573 K)[1]
1510 mg dm−3 [2]
Hazards
R-phrases R36/37/38 [1]
S-phrases S24/25, S22 [1]
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 is MoO3·H2O and the dihydrate (MoO3·2H2O) are well characterized. They are yellow diamagnetic solids.

Structure of the solids[edit]

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[edit]

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.

Applications[edit]

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.

References[edit]

  1. ^ a b c d e "Molybdic acid | 7782-91-4". Chemicalbook.com. Retrieved 2012-08-23. 
  2. ^ http://www.chemspider.com/RecordView.aspx?rid=e75000d7-a392-4602-8ca4-f2bd1f94b31c
  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: 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