Cobalt(II) hydroxide
| Cobalt(II) hydroxide | |
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Cobalt(II) hydroxide |
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Other names
Cobaltous hydroxide, cobalt hydroxide, cobaltous hydrate |
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| Identifiers | |
| CAS number | 21041-93-0  |
| PubChem | 10129900 |
| ChemSpider | 8305419 |
| Jmol-3D images | Image 1 |
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| Properties | |
| Molecular formula | Co(OH)2 |
| Molar mass | 92.948 g/mol |
| Appearance | rose-red powder or bluish-green powder |
| Density | 3.597 g/cm3 |
| Melting point |
168 °C (decomp)[1] |
| Solubility in water | 3.20 mg/L |
| Solubility product, Ksp | 1.0×10−15 |
| Solubility | soluble in acids, ammonia; insoluble in dilute alkalis |
| Structure | |
| Coordination geometry |
rhombohedral |
| Thermochemistry | |
| Std enthalpy of formation ΔfH |
-539.7 kJ·mol−1 |
| Standard molar entropy S |
79.0 J·mol−1·K−1[2] |
| Hazards | |
| MSDS | Oxford University |
| EU classification | Harmful (H) |
| R-phrases | R20 R21 R22 R36 R37 R38 R43 |
| S-phrases | S24 S26 S36 S37 S39[3] |
| NFPA 704 |
 0
1
2
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| Related compounds | |
| Other anions | Cobalt(II) chloride Cobalt(II) bromide Cobalt(II) iodide |
| Other cations | Iron(II) hydroxide Nickel(II) hydroxide Copper(II) hydroxide |
 (verify) (what is:  / ?)Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa) |
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| Infobox references | |
Cobalt(II) hydroxide or cobaltous hydroxide is the chemical compound composed of cobalt and the hydroxide ion with the formula Co(OH)2. It occurs in two forms, either as a rose-red powder, which is the more stable of the two forms, or as bluish-green powder.[1][4] It has the brucite or cadmium iodide crystal structure.[5]
[edit] Uses
It finds use as a drying agent for paints, varnishes and inks, in the preparation of other cobalt compounds, as a catalyst and in the manufacture of battery electrodes[1].
[edit] Reactions
Cobalt(II) hydroxide is precipitated when an alkaline hydroxide is added to an aqueous solution of Co2+ ions:
Cobalt(II) hydroxide decomposes to cobalt(II) oxide at 168 °C under vacuum and is oxidized by air to form cobalt(III) hydroxide, Co(OH)3.[1] The thermal decomposition product in air above 300 °C is Co3O4.[6][7][8]
Like iron(II) hydroxide, cobalt(II) hydroxide is primarily a basic hydroxide, although it does form the weakly acidic reddish hexaaquacobalt(II) ion, [Co(H2O)6]2+, in acidic aqueous solutions. In strong bases, cobalt(II) hydroxide accepts additional hydroxide ions to form dark blue cobaltates(II) [Co(OH)4]2- and [Co(OH)6]4-[5].
[edit] References
- ^ a b c d Patnaik, Pradyot (2003). Handbook of Inorganic Chemical Compounds. McGraw-Hill Professional. p. 243. ISBN 0070494398. http://books.google.com/?id=Xqj-TTzkvTEC&pg=PA243. Retrieved 2009-03-27.
- ^ Lide, David R. (1998). Handbook of Chemistry and Physics (87 ed.). Boca Raton, FL: CRC Press. p. 513. ISBN 0849305942.
- ^ "Safety (MSDS) data for cobalt (II) hydroxide". Oxford University. http://msds.chem.ox.ac.uk/CO/cobalt_II_hydroxide.html. Retrieved 2009-03-27.
- ^ Lide, David R. (1998). Handbook of Chemistry and Physics (87 ed.). Boca Raton, FL: CRC Press. p. 454. ISBN 0849305942.
- ^ a b Wiberg, Nils; Wiberg, Egon; Holleman, A. F. (2001). Inorganic Chemistry. Academic Press. pp. 1478–1479. ISBN 0123526515. http://books.google.com/?id=LxhQPdMRfVIC&pg=PA1478. Retrieved 2009-03-27.
- ^ R. S. Jayashree and P. Vishnu Kamath (1999). "Electrochemical synthesis of a-cobalt hydroxide". Journal of Materials Chemistry 9: 961–963. doi:10.1039/A807000H.
- ^ Synthesis of Co3O4 during thermolysis of cobalt hydroxide and binary hydroxides, L.A. Paikina, S.M. Rakhovskaya, L.A. Vereshchagina, Neorganicheskie Materialy. Vol. 19, no. 9, pp. 1508–11. 1983
- ^ Z. P. Xu and H. C. Zeng (1998). "Thermal evolution of cobalt hydroxides: a comparative study of their various structural phases". Journal of Materials Chemistry 8 (11): 2499–2506. doi:10.1039/A804767G.
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