separation and analysis procedure for the general unknown

A student performed the separation and analysis procedure for the general unknown (Group I, II, and III cations). Her initial separation results are summarized below: – treatment with HCl yielded a white precipitate (part 1) – treatment with thioacetamide yielded an orange/black precipitate (part 2) – a clear, blue/green solution (part 3) The white precipitate from part I was incubated in a hot water bath for 5 minutes. After incubation, the solid was gone. Treatment with potassium chromate resulted in a bright yellow/orange precipitate. The orange/black precipitate from part 2 was redissolved by acidification with nitric acid followed by treatment with ammonia. After the ammonia treatment, the solution turned dark blue. The blue/green solution from part 3 was treated with hydrogen peroxide and potassium hydroxide. A reddish precipitate formed. The mixture was centrifuged and the solid was separated from the solution. Treatment of the solid with ammonia had no effect. Acidification with hydrochloric acid followed by addition of potassium thiocyanate resulted in an intense red/orange solution. The solution from the initial centrifugation step to remove the hydroxide solid was clear and yellow. Treatment of this solution with barium chloride resulted in a yellow/white precipitate. Identify the ions present in the student’s mixture. Draw the appropriate flow chart for each cation (Group I, II, and III on the following pages. (page 2 and 3). Group I ion(s): Group II ion(s): Group III ion(s):


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