3D model (JSmol)
CompTox Dashboard (EPA)
|Molar mass||143.95 g·mol−1|
|Appearance||yellow or light blue solid|
|Melting point||802 °C (1,476 °F; 1,075 K)|
|Boiling point||1,155 °C (2,111 °F; 1,428 K)(sublimes)|
|1.066 g/L (18 °C) |
4.90 g/L (28 °C)
20.55 g/L (70 °C)
|Band gap||>3 eV (direct)|
|Pnma, No. 62|
a = 1.402 nm, b = 0.37028 nm, c = 0.39663 nm
Formula units (Z)
Heat capacity (C)
|75.0 J K−1 mol−1|
|77.7 J K−1 mol−1|
Std enthalpy of
Gibbs free energy (ΔfG˚)
|H319, H335, H351|
|P201, P202, P261, P264, P271, P280, P281, P304+P340, P305+P351+P338, P308+P313, P312, P337+P313, P403+P233, P405, P501|
|NFPA 704 (fire diamond)|
|Lethal dose or concentration (LD, LC):|
LD50 (median dose)
|125 mg.kg (rat, oral)|
2689 mg/kg (rat, oral)
LDLo (lowest published)
|120 mg Mo/kg (rat, oral)|
120 mg Mo/kg (guinea pig, oral)
LC50 (median concentration)
|>5840 mg/m3 (rat, 4 hr)|
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
what is ?)(
Molybdenum trioxide is chemical compound with the formula MoO3. This compound is produced on the largest scale of any molybdenum compound. It is an intermediate in the production of molybdenum metal. It is also an important industrial catalyst. Molybdenum trioxide occurs as the rare mineral molybdite.
In the gas phase, three oxygen atoms are double bonded to the central molybdenum atom. In the solid state, anhydrous MoO3 is composed of layers of distorted MoO6 octahedra in an orthorhombic crystal. The octahedra share edges and form chains which are cross-linked by oxygen atoms to form layers. The octahedra have one short molybdenum-oxygen bond to a non-bridging oxygen. Also known is a metastable (β) form of MoO3 with a WO3-like structure.
MoO3 is produced industrially by roasting molybdenum disulfide, the chief ore of molybdenum:
The laboratory synthesis of the dihydrate entails acidification of aqueous solutions of sodium molybdate with perchloric acid:
The dihydrate loses water readily to give the monohydrate. Both are bright yellow in color.
Molybdenum trioxide dissolves slightly in water to give "molybdic acid". In base, it dissolves to afford the molybdate anion.
Technically pure molybdenum trioxide, the product from the roasting of molybdenum disulfide, is an additive to steel and corrosion-resistant alloys. Chemically pure molybdenum trioxide is used to manufacture molybdenum metal. The relevant conversion entails treatment of MoO3 with hydrogen at elevated temperatures:
Molybdenum trioxide is also a component of the co-catalyst used in the industrial production of acrylonitrile by the oxidation of propene and ammonia.
Because of its layered structure and the ease of the Mo(VI)/Mo(V) coupling, MoO3 is of interest in electrochemical devices and displays. Molybdenum trioxide has also been suggested as a potential anti-microbial agent, e.g., in polymers. In contact with water, it forms H+ ions which can kill bacteria effectively.
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