Devise a test to distinguish between Cu2+ and Co2+.
Couldn't you add HCl to form CoCl4^2-.
To devise a test to distinguish between Cu2+ and Co2+, we can use the differences in their chemical properties and characteristics. Here's a step-by-step experiment you can conduct:
Materials needed:
1. Cu2+ solution (e.g., copper sulfate solution)
2. Co2+ solution (e.g., cobalt chloride solution)
3. Sodium hydroxide (NaOH) solution
4. Ammonium hydroxide (NH4OH) solution
5. Hydrochloric acid (HCl) solution
6. Test tubes or small containers
7. Pipettes or droppers
Procedure:
1. Label two test tubes or small containers as "Cu2+" and "Co2+".
2. Take a small amount of the Cu2+ solution and add it to the test tube labeled "Cu2+". Similarly, take an equal amount of the Co2+ solution and add it to the test tube labeled "Co2+".
3. Now, add sodium hydroxide (NaOH) solution dropwise to both test tubes. Observe any changes that occur.
- Cu2+: Cu2+ ions form a blue precipitate with NaOH due to the formation of copper(II) hydroxide [Cu(OH)2].
- Co2+: Co2+ ions do not produce a visible precipitate with NaOH.
4. Next, add ammonium hydroxide (NH4OH) solution dropwise to both test tubes. Observe any changes.
- Cu2+: If Cu2+ ions are present, the blue precipitate formed in step 3 will dissolve upon the addition of excess ammonium hydroxide.
- Co2+: Co2+ ions do not dissolve or form any significant visible changes with excess ammonium hydroxide.
5. To confirm your results, you can perform a confirmatory test:
- For Cu2+ confirmation: Add a few drops of hydrochloric acid (HCl) to the solution containing Cu2+ ions. If Cu2+ is present, a white precipitate of copper(II) chloride [CuCl2] will form.
- For Co2+ confirmation: Add a small amount of potassium cyanide (KCN) to the solution containing Co2+ ions. If Co2+ is present, a deep red color will develop due to the formation of cobalt(II) cyanide [Co(CN)2].
By following this procedure, you can distinguish between Cu2+ and Co2+ based on their characteristic reactions with sodium hydroxide, ammonium hydroxide, hydrochloric acid, and potassium cyanide. Remember to handle chemicals with caution and follow appropriate safety guidelines when conducting laboratory experiments.