Devise a test to distinguish between Cu2+ and Co2+.
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To devise a test to distinguish between Cu2+ and Co2+, you can use the principle of selective precipitation. By adding specific reagents to the solution containing the metal ions, you can observe the formation of distinct precipitates, which can help differentiate between copper (Cu2+) and cobalt (Co2+).
Here's a test procedure that can be used:
1. Take a small volume of the solution containing Cu2+ and Co2+ ions.
2. To the solution, add a few drops of dilute sodium hydroxide (NaOH) solution.
- Cu2+ ions will form a pale blue precipitate of copper hydroxide (Cu(OH)2), indicating the presence of copper.
- Co2+ ions will not form a precipitate with NaOH at this stage.
3. To further confirm the presence of cobalt ions, add excess ammonia solution (NH3) dropwise to the solution.
- Cu(OH)2 precipitate will remain unchanged.
- Co2+ ions will form a dark green precipitate of cobalt hydroxide (Co(OH)2), confirming the presence of cobalt.
4. If the solution contains Cu2+ and Co2+, then both precipitates will be observed; a pale blue (Cu2+) and a dark green (Co2+).
It is important to note that the concentration of the metal ions and the reactants used may affect the reaction. Therefore, it is recommended to perform this test using proper safety precautions and in a controlled laboratory setting.