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An “unknown” liquid was obtained

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An “unknown” liquid was obtained. Several drops of 6 M HCl were added to this solution and a white precipitate was visible. The test tube is centrifuged, and the solution decanted. The decantate is set aside. 8 drops of DI water, was added the mixture stirred and centrifuged to wash the precipitate. After the tube is centrifuged, the wash water is discarded. 15 drops of DI were added to the precipitate and the tube was placed in a hot water bath for 3 minutes. The precipitate dissolved. Upon adding 4 drops of potassium chromate to the solution, a bright yellow precipitate formed.  

To the liquid decantate, 4 drops of 1 M thioacetamide was added and the solution was mixed and heated in a hot water bath. A noticeable black precipitate formed. The test tube was removed from the hot water bath, centrifuged and the liquid decanted and set aside. 8 drops of 6 M HNO3 were added to the precipitate and the test tube was heated in a hot water for 2 minutes. The test tube was removed from the hot water bath, allowed to cool for a minute and 12 drops of concentrated NH4OH were added producing a deep wildcat blue color.

Highlight the cation that is definitely NOT PRESENT in the unknown.

Ag+         Pb2+ Cu2+            Fe3+ Co2+ Ni2+ Ca2+ Ba2+