Cobalt(III) oxide is the inorganic compound with the formula of Co2O3. Although only two oxides of cobalt are well characterized, CoO and Co3O4, procedures claiming to give Co2O3 have been described. Thus treatment of Co(II) salts such as cobalt(II) sulfate with an aqueous solution of sodium hypochlorite (also known as bleach) gives a black solid:
2CoSO4 + 4NaOH + NaOCl → Co2O3 + 2Na2SO4 + NaClSome formulations of the catalyst hopcalite contain "Co2O3".
Some studies have been unable to synthesize the compound, and report that it is theoretically unstable.
It is soluble in cold diluted sulfuric acid and produces Co2[SO4]3, which is blue in aqueous solution.
Co2O3 + 3H2SO4 → Co2[SO4]3 + 3H2OCobalt(III) ion is a strong oxidizer in acidic solution, its standard electrode potential is +1.84V in this situation.
See also
References
Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. ISBN 978-0-08-037941-8. 978-0-08-037941-8 ↩
Handbook of Preparative Inorganic Chemistry, 2nd Ed. Edited by G. Brauer, Academic Press, 1963, NY. p. 1675. ↩
Hüttner, Erwin (1901-05-02). "Beiträge zur Kenntnis der Oxyde des Kobalts". Zeitschrift für anorganische Chemie (in German). 27 (1). Wiley: 81–124. doi:10.1002/zaac.19010270113. ISSN 0863-1778. https://zenodo.org/record/2455069 ↩
Shanbhag, Pavitra N.; Biswas, Raju K.; Pati, Swapan K.; Sundaresan, Athinarayanan; Rao, Chinthamani Nagesa Ramachandra (2020-11-02). "Elusive Co2O3: A Combined Experimental and Theoretical Study". ACS Omega. 5 (45). American Chemical Society (ACS): 29009–29016. doi:10.1021/acsomega.0c03397. ISSN 2470-1343. PMC 7675568. PMID 33225132. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7675568 ↩
Guoqing, Wu (2003). 无机化学 (Inorganic Chemistry) (4th ed.). People's Republic of China: 高等教育出版社 (Higher Education Press). p. 781. ISBN 9787040115833. 9787040115833 ↩