Cobalt - 27Co: reactions of elements
Reaction of cobalt with air
Cobalt is not particularly reactive with air. However on heating the oxide Co3O4 is formed. If the reaction is carried out above 900°C, the result is cobalt(II) oxide, CoO. Cobalt does not react directly with nitrogen, N2.
3Co(s) + 4O2(g) → 2Co3O4(s)
2Co(s) + O2(g) → 2CoO(s)
Reaction of cobalt with water
Water has little effect upon cobalt metal. The reaction between red hot cobalt metal and steam produces cobalt(II) oxide, CoO.
2Co(s) + O2(g) → 2CoO(s)
Reaction of cobalt with the halogens
The dibromide cobalt(II) bromide, CoBr2, is made through the direct reaction between cobalt metal and bromine.
Co(s) + Br2(l) → CoBr2(s) [green]
The corresponding chloride and iodide may be made in the same way, but other methods seem to be used in preference forsynthetic use.
Co(s) + Cl2(g) → CoCl2(s) [blue]
Co(s) + I2(s) → CoI2(s) [blue-black]
Reaction of cobalt with acids
Cobalt metal dissolves slowly in dilute sulphuric acid to form solutions containing the aquated Co(II) ion together with hydrogen gas, H2. In practice, the Co(II) is present as the complex ion [Co(OH2)6]2+.
Co(s) + H2SO4(aq) → Co2+(aq) + SO42-(aq) + H2(g)