Question

How can I separate Zn^2+ , Cu^2+ and Al^3+? Using centrifugation, Sodium hydroxide, Nitric acid and potassium ferrocyanid.

Answer 1

To Zn²⁺ add 6 M HCl solution drop wise until the liquid is acidic. Add 3 drops of 0.1 M K4[Fe(CN)6] and stir the mixture. Centrifuge the test tube. If there is a precipitate in the test tube, then there are Zn2+ ions present.

To Al^3+, add 10 drops of 6 M HNO3 solution to Test Tube 5. Check the pH of the solution. If it is not acidic, add more 6 M HNO3 drop wise until the solution becomes acidic. Add 6 M NH3 solution dropwise until the solution is basic, and then add an additional 3 drops of 6 M NH3. Stir the mixture. Centrifuge the test tube and check again for the precipitate.

To Cu2+, add NaOH drop wise to until the solution is basic, Cu2+, precipitated as Cu(OH)₂

Centrifuge the test tube and decant the liqiuid.