Molybdenum(IV) oxide Chemical Properties

Melting point:

decomposes [JAN85]

Density 

6.47 g/mL at 25 °C (lit.)

solubility 

insoluble in H2O, acid solutions, alkaline solutions

form 

Powder

color 

Red-brown

Specific Gravity

6.47

Water Solubility 

slightly soluble H2SO4; insoluble HCl, HF, and alkalies [HAW93]

Crystal Structure

MoO2 type

crystal system

Monoclinic

Space group

P21/c

Lattice constant

a/nm	b/nm	c/nm	α/o	β/o	γ/o	V/nm3
0.55388	0.48562	0.56285	90	119.683	90	0.1315

Exposure limits

ACGIH: TWA 10 mg/m3; TWA 3 mg/m3
NIOSH: IDLH 5000 mg/m3

InChIKey

QXYJCZRRLLQGCR-UHFFFAOYSA-N

CAS DataBase Reference

18868-43-4(CAS DataBase Reference)

EPA Substance Registry System

Molybdenum oxide (MoO2) (18868-43-4)

Safety Information

Hazard Codes 

Xn

Risk Statements 

20/21/22-36/37/38

Safety Statements 

26-36

WGK Germany 

1

RTECS 

QA4688000

TSCA 

Yes

HS Code 

28257000

Toxicity

mouse,LD50,subcutaneous,318mg/kg (318mg/kg),Zhurnal Vsesoyuznogo Khimicheskogo Obshchestva im. D.I. Mendeleeva. Journal of the D.I. Mendeleeva All-Union Chemical Society. Vol. 19, Pg. 186, 1974.

MSDS

• Language:English Provider:SigmaAldrich
• Language:English Provider:ALFA

Molybdenum(IV) oxide Usage And Synthesis

Chemical Properties

Lead-gray, nonvolatile powder. Dapproximately 6.4. Insoluble in hydrochloric acidand hydrogen fluoride and alkalies, sparingly solu-ble in sulfuric acid.

Physical properties

Molybdenum(IV) oxide can be prepared by several methods including controlled oxidation of Mo and controlled reduction of MoO3 with hydrogen. The pure oxide suitable for structure determination has been prepared by electrolysis of a polymolybdate (K2O5.MoO3) solution. Molybdenum(IV) oxide is insoluble in water: it is inert in solutions of nonoxidizing acids or bases, but is dissolved by oxidizing solutions. It dissociates to Mo and MoO3 at high temperatures (~ 1100°).
Crystalline MoO2 is violet or brown. Its deformed rutile structure consists of infinite chains of MoO6 octahedra sharing opposite edges along the chain direction with Mo-Mo distances alternately long (3.10 A) and short (2.50 A). It is diamagnetic and semiconducting ; metal-metal bonds are present. Some of its thermodynamic properties are as follows: G°f29% ~ 172.415 kcal/mole H°f29% -140.5 kcal/mole S°298 11.954 gibbs/mole.

Uses

Molybdenum(IV) oxide (MoO2) is a transition metal oxide with good electrical conductivity due to the presence of delocalized electrons in its valence band. It is traditionally prepared by reducing MoO3 in dry hydrogen in the temperature range of 450-550°C.
MoO2 can be used in a variety of energy based applications such as an anode material in rechargeable lithium batteries and fuel flexible solid oxide fuel cells.It can also be used as a catalyst in hydrogen reforming processes.

Uses

Molybdenum(IV) oxide is used to catalyze the dehydrogenation of alcohols. It is also used as an intermediates and processing aids. It finds application in the manufacture of molybdenum nano-wires.

Preparation

Molybdenum(IV) oxide is obtained by passing steam over red hot molybdenum:
Mo + 2H2O → MoO2 + 2H2
Alternatively, the oxide may be prepared by heating a molybdate salt, such as ammonium molybdate, with a reducing agent such as zinc. The dioxide also may be obtained along with other oxides of molybdenum when molybdenum metal is heated in air.
A brown-black suspension of MoO2 in hydrate form may be obtained by reducing a solution of ammonium molybdate with hydrogen in the presence of colloidal palladium.

General Description

Molybdenum(IV) oxide (MoO₂) is a transition metal oxide with good electrical conductivity due to the presence of delocalized electrons in its valence band. It is traditionally prepared by reducing MoO₃ in dry hydrogen in the temperature range of 450-550°C.

Hazard

Toxic material.

Safety Profile

Poison by subcutaneous route. Incandescent reaction with air. When heated to decomposition it emits toxic fumes of Mo.

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