Manganese(II) oxide

Manganese(II) oxide is an inorganic compound with chemical formula MnO.[2] It forms green crystals. The compound is produced on a large scale as a component of fertilizers and food additives.

Manganese(II) oxide
Names
IUPAC name
Manganese(II) oxide
Other names
Manganous oxide
Manganosite
manganese monoxide
Hypomanganous oxide
oxomanganese
Identifiers
ECHA InfoCard 100.014.269
RTECS number
  • OP0900000
UNII
Properties
MnO
Molar mass 70.9374 g/mol
Appearance green crystals or powder
Density 5.43 g/cm3
Melting point 1,945 °C (3,533 °F; 2,218 K)
insoluble
Solubility soluble in acid
+4850.0·10−6 cm3/mol
2.16
Structure
Halite (cubic), cF8
Fm3m, No. 225
Octahedral (Mn2+); octahedral (O2−)
Thermochemistry
60 J·mol−1·K−1[1]
Std enthalpy of
formation (ΔfH⦵298)
 −385 kJ·mol−1[1]
Hazards
NFPA 704 (fire diamond)
Flammability code 0: Will not burn. E.g. waterHealth code 1: Exposure would cause irritation but only minor residual injury. E.g. turpentineReactivity code 0: Normally stable, even under fire exposure conditions, and is not reactive with water. E.g. liquid nitrogenSpecial hazards (white): no code
0
1
0
Flash point Non-flammable
Related compounds
Other anions
 Manganese(II) fluoride
Manganese(II) sulfide
Other cations
 Iron(II) oxide
Manganese(II,III) oxide
Manganese(III) oxide
Manganese dioxide
Manganese heptoxide
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Infobox references

Structure, stoichiometry, reactivity

Like many monoxides, MnO adopts the rock salt structure, where cations and anions are both octahedrally coordinated. Also like many oxides, manganese(II) oxide is often nonstoichiometric: its composition can vary from MnO to MnO1.045.[3]

Below 118 K MnO is antiferromagnetic.[3] MnO has the distinction of being one of the first compounds[4] to have its magnetic structure determined by neutron diffraction, the report appearing in 1951.[5] This study showed that the Mn2+ ions form a face centered cubic magnetic sub-lattice where there are ferromagnetically coupled sheets that are anti-parallel with adjacent sheets.

Manganese(II) oxide undergoes the chemical reactions typical of an ionic oxide. Upon treatment with acids, it converts to the corresponding manganese(II) salt and water.[3] Oxidation of manganese(II) oxide gives manganese(III) oxide.

Preparation and occurrence

MnO occurs in nature as the rare mineral manganosite.
Commercially it is prepared by reduction of MnO2 with hydrogen, carbon monoxide or methane, e.g.:[2]

MnO2 + H2 → MnO + H2O
MnO2 + CO → MnO + CO2

MnO can also be prepared by decarbonation of the carbonate:[6]

MnCO3 → MnO + CO2

This calcining process is conducted anaerobically, lest Mn2O3 form.

An alternative route, mostly for demonstration purposes, is the oxalate method, which also applicable to the synthesis of ferrous oxide and stannous oxide. Upon heating in an oxygen-free atmosphere (usually CO2), manganese(II) oxalate decomposes into MnO:[7]

MnC2O4·2H2O → MnO + CO2 + CO + 2 H2O

Applications

Together with manganese sulfate, MnO is a component of fertilizers and food additives. Many thousands of tons are consumed annually for this purpose. Other uses include: a catalyst in the manufacture of allyl alcohol, ceramics, paints, colored glass, bleaching tallow and textile printing.[2]

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References
  1. Zumdahl, Steven S. (2009). Chemical Principles 6th Ed. Houghton Mifflin Company. p. A22. ISBN 0-618-94690-X.
  2. Arno H. Reidies "Manganese Compounds" Ullmann's Encyclopedia of Chemical Technology 2007; Wiley-VCH, Weinheim. doi:10.1002/14356007.a16_123
  3. Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. ISBN 978-0-08-037941-8.
  4. J.E Greedon, (1994), Magnetic oxides in Encyclopedia of Inorganic chemistry Ed. R. Bruce King, John Wiley & Sons ISBN 0-471-93620-0
  5. Neutron Diffraction by Paramagnetic and Antiferromagnetic Substances C. G. Shull, W. A. Strauser, and E. O. Wollan, Phys. Rev. 83, 333 - 345 (1951), doi:10.1103/PhysRev.83.333
  6. W.H. McCarroll (1994) Oxides- Solid State Chemistry, Encyclopedia of Inorganic Chemistry Ed. R. Bruce King, John Wiley & Sons ISBN 0-471-93620-0
  7. Arthur Sutcliffe (1930) Practical Chemistry for Advanced Students (1949 Ed.), John Murray - London.
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