Molybdic acid

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Crystal structure
Crystal structure of white molybdic acid
__ Mo 6+      __ O 2−
crystal structure of H 2 MoO 4
General
Surname Molybdic acid
other names

Molybdenum (VI) acid

Ratio formula MoO 3 · H 2 O
Brief description

colorless (triclinic) or yellow (monoclinic) solid

External identifiers / databases
CAS number 7782-91-4
EC number 231-970-5
ECHA InfoCard 100.029.063
PubChem 82208
Wikidata Q412950
properties
Molar mass 161.95 g mol −1
Physical state

firmly

Melting point

300 ° C (85%)

pK s value
  • pK s 1 = 3.7
  • pK s 2 = 3.9
solubility

0.5 g l −1 (monohydrate, 15 ° C)

safety instructions
GHS labeling of hazardous substances
08 - Dangerous to health 07 - Warning

Caution

H and P phrases H: 319-335-373
P: 305 + 351 + 338
As far as possible and customary, SI units are used. Unless otherwise noted, the data given apply to standard conditions .

Molybdic acid has the empirical formula H 2 MoO 4 and can be used as monohydrate of molybdenum trioxide be construed: MoO 3 · H 2 O. In contrast about the seemingly analogue construction of sulfuric acid (H 2 SO 4 ), there are no discrete H 2 MoO 4 - molecules , instead, is molybdic acid of a layer lattice of MoO 6 - octahedra (yellow, monoclinic form) or zig-zag chains of MoO 6 octahedra (colorless, triclinic form). The conjugate base of molybdic acid MoO 4 2− is called molybdate , the salts of molybdic acid are called molybdates . Like the sulfate ions , the molybdate ions consist of MoO 4 2− tetrahedra.

Molybdate (MoO 4 2− ) is the bioavailable form of molybdenum , that is, it can be used by living things .

Molybdic acid can be obtained as a white precipitate if a molybdate solution is acidified. Nitric acid molybdate solutions can also deposit the yellow hydrate of molybdic acid H 2 MoO 4 · H 2 O in crystalline form if left standing for a long time .

Individual evidence

  1. a b c d e A. F. Holleman , E. Wiberg , N. Wiberg : Textbook of Inorganic Chemistry . 101st edition. Walter de Gruyter, Berlin 1995, ISBN 3-11-012641-9 .
  2. a b c Datasheet Molybdic acid about 85% MoO 3 , contains ammonium molybdate (PDF) from Merck , accessed on April 11, 2011.
  3. ^ D'Ans-Lax: Taschenbuch für Chemiker und Physiker , 4th edition, Volume 3, Springer Verlag 1998, ISBN 3-540-60035-3 .
  4. ^ Schwarz G. et al .: Molybdenum cofactors, enzymes and pathways . In: Nature . 460, No. 7257, 2009, pp. 839-847. PMID 19675644 .
  5. Jander-Blasius, Textbook of analytical and preparative inorganic chemistry, 8th edition, S. Hirzel Verlag, Stuttgart 1969.