Manganese(II) oxide
| Manganese(II) oxide | ||
|---|---|---|
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| IUPAC name Manganese(II) oxide | ||
| Other names Manganous oxide | ||
| Identifiers | ||
| CAS number | 1344-43-0  | |
| PubChem | 14940 | |
| RTECS number | OP0900000 | |
| Properties | ||
| Molecular formula | 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 | |
| Solubility in water | insoluble | |
| Solubility | soluble in acid | |
| Refractive index (nD) | 2.16 | |
| Structure | ||
| Crystal structure | Halite (cubic), cF8 | |
| Space group | Fm3m, No. 225 | |
| Coordination geometry |
Octahedral (Mn2+); octahedral (O2–) | |
| Thermochemistry | ||
| Std enthalpy of formation ΔfH |
−385 kJ·mol−1[1] | |
| Standard molar entropy S |
60 J·mol−1·K−1[1] | |
| Hazards | ||
| EU Index | Not listed | |
| Flash point | Non-flammable | |
| Related compounds | ||
| Other anions | Manganese difluoride Manganese(II) sulfide | |
| Other cations | Iron(II) oxide | |
| Related manganese oxides | Manganese(II,III) oxide Manganese(III) oxide Manganese dioxide Manganese heptoxide | |
(verify) (what is: / ?)Except where noted otherwise, data are given for materials in their standard state (at 25 °C (77 °F), 100 kPa) | ||
| Infobox references | ||
Manganese(II) oxide (systematically named manganese(2+) oxide(2−)) is an inorganic compound with chemical formula MnO.[2] It forms green crystals and is odorless. Manganese(II) oxide is the simplest ionic manganese oxide. Although it is classified as a very strong base, dissolved manganese(II) oxide is non-corrosive and does not attack the skin.
Chemical properties
Basicity
The oxide anion (O2−) in ionic manganese oxides such as manganese(II) oxide can assimilate a proton by recombination:
- O2− + H+ → HO−
Because of this capture of a proton (H+), manganese(II) oxide has basic character. In aqueous solution, it has a pKb value of ~−38. Oxide's conjugate acid is hydroxide (OH−). A saturated solution has a near neutral pOH, indicating that most oxide ions are associated.
- O2− + H2O
2 HO−
Structure
MnO has the NaCl, rock salt structure, where cations and anions are both octahedrally coordinated.[3] The composition of MnO 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 in 1951.[5] This study showed that the Mn2+ ions form a face centered cubic magnetic sub-lattice where there are ferromagnetically coupled sheets which are anti-parallel with adjacent sheets.
Chemical reactions
Manganese(II) oxide undergoes the typical chemical reactions of an ionic manganese oxide. Upon treatment with a standard acid, it converts to a manganese(II) salt and water.[3] Oxidation of manganese(II) oxide gives manganese dioxide.
Preparation and occurrence
MnO can be prepared by the reduction of any higher oxide with hydrogen[3] e.g.:
- MnO2 + H2 → MnO + H2O
Commercially it is prepared by reduction of MnO2 with hydrogen, carbon monoxide or methane:[2]
- MnO2 + CO → MnO + CO2
MnO can also be prepared by heating MnCO3:[6]
- MnCO3 → MnO + CO2
This calcining process is conducted anaerobically to prevent formation of Mn2O3. MnO occurs in nature as the rare mineral manganosite.
Applications
Together with manganese sulfate, MnO is a component of fertilizer and food additives. Many thousands of tons are consumed annually for this purpose.[2]
Other uses include: a catalyst in the manufacture of allyl alcohol, ceramics, paints, colored glass, bleaching tallow and textile printing.
References
- ↑ 1.0 1.1 Zumdahl, Steven S. (2009). Chemical Principles 6th Ed. Houghton Mifflin Company. p. A22. ISBN 0-618-94690-X.
- ↑ 2.0 2.1 2.2 Arno H. Reidies "Manganese Compounds" Ullmann's Encyclopedia of Chemical Technology 2007; Wiley-VCH, Weinheim. doi:10.1002/14356007.a16_123
- ↑ 3.0 3.1 3.2 3.3 3.4 Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. ISBN 0080379419.
- ↑ J.E Greedon, (1994), Magnetic oxides in Encyclopedia of Inorganic chemistry Ed. R. Bruce King, John Wiley & Sons ISBN 0-471-93620-0
- ↑ 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
- ↑ W.H. McCarroll (1994) Oxides- solid sate chemistry, Encyclopedia of Inorganic chemistry Ed. R. Bruce King, John Wiley & Sons ISBN 0-471-93620-0
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