Transition elements
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Describe a chemical test that could be used to distinguish cobalt from copper.
080608
Igloo writes ....
By "cobalt" and "copper" I presume that you referring to compounds containing these two metals. Compounds of cobalt normally contain Co2+ ions and when dissolved in water give pink solutions owing to the presence of the hexaaquacobalt(II) complex, [Co(H2O)6]2+. Copper compounds in solution are invariably ones containing Cu2+ ions, and are generally blue in colour owing to the presence of hexa-aquacopper(II) ions, [Cu(H2O)6]2+.
If a small volume of concentrated hydrochloric acid is added to a sample of each of these solutions, the one containing cobalt(II) ions will turn blue due to the formation of tetrachlorocobalt(II) ions, [CoCl4]2-, whereas the solution containing copper(II) ions will turn yellow/green because tetrachlorocopper(II) ions, [CuCl4]2- are formed.
If you are referring in your question to the metals themselves, then you will have to dissolve small pieces in moderately concentrated nitric acid in order to produce the ions mentioned earlier.
The tests I have described are probably the most straightforward to carry out and give quick and easily observable results.
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updated: 18 June 2008
