QUALITATIVE ANALYSIS OF GROUP II CATIONS INTRODUCTION Qualitative analysis is a

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QUALITATIVE ANALYSIS OF GROUP II CATIONS INTRODUCTION Qualitative analysis is a method for identifying the elements present in a unknown mixture. metal cations are classified into three i groups based upon their solubilities are those which form insoluble chlorides. Group II form insoluble sulfides below pH 0.5 while group III Fe Mn. Ni3, and Zn, form insoluble sulfides above pH9. Finally, the are the remaining common cations. The alkaline earth members of this group form insoluble carbonates while the alkaline elements are The group I cations, Pb Ag', and cations, AP, Cr identified by flame tests. The ammonium ion is detected by a litmus test. These groups are easily separated by their markedly different solubilities. within a given group is more difficult but based upon the same principle, as will be shown in the NOTE: THE GROUPS USED FOR QUANTITATIVE ANALYSIS ARE SOLELY BASED ON SOLUBILITY. THEY DO NOTIN ANY WAY CORRESPOND TO THE GROUPS OF THE PERIODIC TABLE EXPERIMENTAL Obtain a 1mL sample of stock solution containing Cu, Bi one drop of 6 M HCI for every 1 mL of solution in order to adjust the pH of the solution to 0.5. You may test the pH using methyl violet indicator. This can be accomplished M HCI on the first spot. The green color produced will be your standard for a pH of 0.5. Test your standard HCL two spots of methyl violet indicator on a piece of filter .After the pH is correct, add 15 drops of 1 M thioacetamide to the test tube. Stir the solution and heat in a boiling water bath for 5 minutes. Centrifuge, decant the liquid, and save both the and the precipitate. Add two more drops of thioacetamide to the more thioacetamide and centrifuge again. Discard the liquid and combine Wash the precipitate with 2 mL or I M NH,CI solution Stir and heat in the boiling water bath for several minutes. Centrifuge and discard the liquid. liquid NOTE: MAKE SURE THATTHE CENTRIFUGE IS BALANCED ATALL TIMES. Add 2 mL of 1 M NaOH to the r 2 minutes. Centrifuge and separate the from the solid, saving both portions. Repeat the procedure by adding a second 2 mL of 1 M heat the solution in the NaOH to the precipitate and heat the solution in the boiling water bath for 2 minutes. Centrifu use the liquid in part F deionized water. Centrifuge each time and discard the minutes in the boiling water bath. Centrifuge the solution and again and combine the two portions of liquid. Save both the combined liquid and the solid, you will Af this point, tin and antimony will be present in the liquid portion as soluble complex ions and bismuth and copper sulfides will be in the precipitate. Wash the precipitate twice with 3 mL of Add 2 mL of 6 MHNO, to the precipitate and heat it for two liquid into a 30 mL beaker Carefully boil off half of the liquid..

Explanation / Answer

2.
Precipitation of Tin (IV) sulfide with H2S
Sn+2 (aq) + 2 H2S (aq) -------> SnS2 (s) + 2 H+ (aq)
The confirming test for Tin
Sn2+ (aq)  + 2 HgCl2 (aq) ---------> Sn4+ (aq) + Hg2Cl2 (s) + 2 Cl- (aq)
The confirming test for copper
Cu+2 (aq) + K4[Fe(CN)6] (aq) -------> [CuFe(CN)6] (s)

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