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Procedure Separation and Identification of Pb2 (aq), Fe (aq), Al(a), and Cu Note: Tests should be performed concurrently on the known and the unknown solutions. Volumes are approximate. All work excepting the centrifugation should be done in the fume hood 1. To about 2. mL of your sample in a test tube, add 5 drops (-0.2 mL) of 6 M HCl(a). Mix well and centrifuge. Decant the clear liquid into a clean test tube and save it for Step 3 Add 1 drop of HCl(aq) to it to make sure the precipitation is complete. If a precipitate forms, mix well and centrifuge again. Decant the clear liquid into a clean test tube and save it for Step 3 2. The precipitate obtained by the addition of HCl to the test solution is PbCl. To the precipitate from Step 1, add 2.5 mL of distilled water and heat in a boiling water bath for at least three minutes, stirring constantly. The precipitate should dissolve. To confirm the presence of lead, add a few drops of 1 M K,Cr04(aq) to the clear liquid. The formation of a yellow precipitate of PbCrO,(s) confirms the presence of lead. 3. Test the clear liquid from Step 1 with pH paper. It should have a pH of about 0.3. Add 0.5 mL of 1 M thioacetamide and mix well. Heat the test tube for at least 5 minutes in a boiling water bath. Cu and any Pb2 remaining from Step 1 will precipitate as CuS andPbS. Continue to heat the test tube for another 2 minutes to complete the precipitation. Centrifuge and decant the clear solution into a clean test tube. Save it for Step 7. To the precipitate from Step 3, add 0.5 mL of water and 0.5 mL of 6M HNO,. Heat the test tube in a boiling water bath until the reaction is complete. The resulting solution will contain Cu2 and any Pb2 that was not completely precipitated in Step 1 4 5. Cool the solution from Step 4 and then add 6 M NH, mixing well, until the solution is basic to litmus paper. Add an additional few drops of the 6M NHz. Ifthe resulting solution is deep blue, it indicates the presence of the Cu(NHcmplex ion To confirm the presence of copper, add 6 M acetic acid to the blue solution from Step 5 , mixing well, until the colour fades and the solution is acidic to litmus. Then add a drop or two of 0.1 M K,Fe(CN) which forms a red-brown precipitate of Cu2Fe(CN)s if copper s present 7.To the clear solution from Step 3, add 0.2mL of 6 M HCl, mix well and centrifuge Discard the precipitate. To the clear solution, add 0.5 mL of 3% H2O2 (hydrogen peroxide) and then, drop by drop, 6 M NaOH(aq), mixing well, until the solution is basic Then add a few drops more. Mix for a minute, boil for 2 to 3 minutes and then centrifuge. Decant the clear solution into a test tube and save for Step 9. The precipitate is Fe(OH),. How do you know that it cannot be Fe(OH)2?. To confirm the presence of iron, add 0.5 mL of water and 0.5 mL of 6 M H2SO,(a) to the precipitate from Step 7. Stir for a minute or two and centrifuge the solution if it is not clear. Take half of the clear solution, add 1 or 2 drops of 0.1 M KSCN(aq) (potassium thiocyanate). Formation of a deep red solution of the FeSCN2(aq) complex ion confirms the presence of iron To the clear filtrate from Step 7 add 6 M HNO3(aq) slowly, and mixing well, until the solution is acidic. If necessary, reduce the volume to 1.5 to 2 mL by boiling it down Add 6 M NH,(aq) drop by drop until the solution is basic to litmus. Stir for a minute or two. A light, gelatinous precipitate of Al(OH), indicates the presence of aluminum. To confirm the presence of aluminum, centrifuge the product of Step 9 and then dissolve the precipitate in 0.5 mL of 6 M HNO3(aq). Add 0.5 mL of water and 1 drop of aluminon reagent and stir. At this point the solution is pink. Add 6 M NH,(aq) drop by 10..

drop, stirring well, until the solution becomes basic to litmus. Al(OH)3(s) should reform and adsorb the red colour from the test reagent, leaving the solution essentially colourless. Centrifuge and check the colour of the solution 11.At the end of the lab, test tubes should be rinsed with water, the rinse being put in the chemical waste bottles in the common fumehood. Used test tubes and Pasteur pipettes should be put in the green pails in the common fume hood and rubber bulbs should be returned to the common bench.2. Complete the Flow Chart, showing the complete analytical scheme and all of the confirmatory tests for the ions. Flow Chart for the Separation Scheme for Pb2*, Fe, A, and Cu* Mixture of Pb2*, Fe*, Al+ and Cu HCI(aq) white precipitate PbCl2(s) filtrate Fe3, Al+, Cu2 and some Pb2 thioacetamide precıpitate CuS and PbS filtrate Fe and APb s) Thioa cafa mid Fe 3r and A1 Adl Hcl filtrate cleay soluh on Pre eipitate Cus and Ph Add HN03 ade heon Sota hHon adc Cea Pre cipi tate del d N H3 deepblue Soluhon whiinos CAl3+ deep Add acutie acid red Soluhin add HNos JA la mínar Reddish brown Ppt Pink Solutiovn

Question:

After reference to the Flow Chart, write equations for each of the reactions involved in the separation olf Pb2+(aq), Fe3+(aq)、Al3+(aq) and Cu2+·Note the colours of any precipitates formed and the colours of any solutions.

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Cr) Yenew celo叼 2十 aua Reddish brou n fsciptat る+ aidic mediow oud nediom Complst Caluminon guogent) Pink outic

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