CHEM 1&2 Lab Manual & worksheets pg 196

CHEM 1&2 Lab Manual & worksheets pg 196 -...

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Experiment 19: Qualitative Analysis General Chemistry I and II Lab Manual Dakota State University page 196 of 232 Check the pH of the decantate and be sure it is still acidic. Add two more drops of thioacetamide, and heat. If a precipitate forms, centrifuge and add the solid to the precipitate to that from the previous step. Repeat this step until addition of thioacetamide produces no more precipitate. Keep the liquid as it contains groups III through V ions. Separation of Sn +4 from Pb +2 , Bi +3 , Cu +2 : To the precipitate, add 1 mL of ammonium sulfide and agitate the solution. Tin should dissolve into the liquid, while other ions remain solid. Centrifuge and decant. Verification of Sn +4 : Add dilute HCl to the decantate from the previous step until it registers acidic to
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Unformatted text preview: litmus paper. Formation of a precipitate indicates the presence of tin. Separation of Pb +2 Bi +3 , and Cu +2 from other impurities: To the precipitate from the separation of tin step, add 1 mL of dilute nitric acid. All ions should dissolve, leaving behind only solid impurities. Centrifuge and decant. Discard any remaining precipitate; separate the decantate into three portions. Verification of Pb +2 : Sn(SO4)2 Sn+4 H2SO4 PbSO4 Pb+2 H2SO4 Cu(NH3)4+2 Cu+2 NH4OH Bi(OH)3 Bi+3 NH4OH PbS, CuS, Bi2S3 Nitric Acid PbS, CuS, Bi2S3, SnS4 (NH4)2S Groups III-V Pb+2, Cu+2, Bi+3, Sn+4, groups III - V HCl/Thioacetamide...
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