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Pre-Laboratory Assignment for Week #2 of: Separation and Identification of Metal Cations DEVELOP A FLOW SCHEME FOR SEPARATING THE CATIONS Based on knowledge of how various precipitates can form, and what reagents can be used to dissolve them, you should be able to build a separation scheme of the type outlined in the introduction to this experiment. That is, you now know enough chemistry to be able to begin with a test tube containing all four ions in solution and separate those ions so that you end up with the four ions each in a separate test tube. At least three or four different separation schemes are possible. Experience has shown, though, that the most successful schemes involve separating the Pb2+ ion from the mixture as early in the scheme as possible. Draw your scheme in your Notebook. Each substance must be represented by its correct formula, for example Al³(aq) or Al(OH)4 (aq) for ions or Al(OH)3(s) for a precipitate of aluminum hydroxide. Indicate the states as shown,i.e. (aq), (s). You will show this flow scheme to your instructor before testing it on an unknown. Be detailed and NEAT. Hints for developing a scheme: (a) Three steps are needed to achieve a separation of the four cations from each other. Use one of the reagents (HCI, NH3, or NaOH) in each step. (b) It is best to separate Pb²+ ion from the others in the first step. (c) When your scheme calls for NH3 or NaOH, use an excess of the reagent. (d) There are several ways to achieve separation and identification. No single scheme is better than others.