Group 1, the Chloride Group BACKGROUND The precipitating reagent for the chloride group is chloride ion in an acidic solution. Only three of the 18 metal ions form a precipitate with this reagent: silverion (A’l, mercury long . and lead ion (Pb”). Since lead chloride is somewhat soluble, it is not completely precipitated here, and a low concentration of lead ion appears also in Group II. We will be using silver and lead in Group L Procedure Before starting analysis, complete the Chloride group flowchart Note: You may experience some difficulty in identifying the ions in your unknown, or you may be uncertain about whether a quantity of precipitate indicates that an ion is present or not. A side- by-side comparison of tests with a solution known to contain the suspected ion will be very helpful in such cases. Precipitation Reactions of Group I Ag* (aq) + Cl(aq) AgCl (s, white) Pb2+ (aq) + C (aq) = PbCl2 (s, white) Group 1: The Chloride Group Add 3 drops of 6 M HCI to 3 mL of the test solution, and mix thoroughly by stirring the mixture with a glass stirring rod. Centrifuge, decant the centrifugate (solution), and test for completeness of precipitation by adding 1 to 2 more drops of 6 M HCI. If no more precipitate forms, precipitation is complete and the liquid (S1) may be discarded if only Group I ions are possible in this unknown. If the unknown possibly contains ions from groups II-IV, SI must be saved. In this case, stopper and label the test tube containing S1 for later analysis. Wash the residue (RI) with 1 to 3 mL of distilled water from your wash bottle, stir, centrifuge, decant, and discard the wash liquid. The residue Rl is now ready for further analysis of the ions in Group L. If no residue forms upon addition of 6 M HCl, neither Ag or Pb ions in Group I is present and further analysis of Group I is unnecessary. Test for Lead Ion PbCl2 (s) + heat=Pb (aq) + 2 CF (aq) Pb (aq) + CO2 (aq) = PbCrO. (s, yellow) Add 3 to 4 ml of distilled water to residue Rl and heat the mixture to near boiling while stirring. Centrifuge the mixture and decant the solution (S2). Wash the remaining residue (R2) with 10 mL of boiling distilled water in portions, centrifuge, and discard these washings. The washings from this precipitation must be discarded in a container labeled qualitative analysis solutions Add several drops of MK.CO to the centrifugate (S2). A yellow precipitate confirms the presence of Pb

Group 1, the Chloride Group Test for Silver lon AgCl (8) + 2NH: (aq) Ag(NH3)2 (aq) + Cl(aq) Ag(NH3)2 (aq) + Cl(aq) + 2 H (aq) = AgCl (s, white) + 2 NH4+ (aq) Add 1 mL of 6 M NH, (aq) and then 2 mL of water with stirring to residue R2. Centrifuge and decant. If S3 is not perfectly clear, it may be due to colloidal Pb(OH)Cl resisting centrifugation. In this case, re-centrifuge the solution as often as necessary until a clear liquid is obtained. Then acidify S3 by adding 6 M HNO, dropwise with stirring until a piece of blue litmus paper turns red. Note: you can use a drop of the solution from your stir rod to touch the litmus paper. A white precipitate confirms the presence of Agt. Disposal: All solutions should be discarded in the waste container.

Group I, the Chloride Group Flowchart for Group I Оооооо

Group I, the Chloride Group PRE-LAB Name: 1. Which chloride of Group I metal ions (Ag and Pb2+) is less soluble? 2. When NH, is added to the solid, R2, which metal ion goes into solution? 3. What is the purpose of precipitation Age and Pbit out of solution at the beginning of the procedure? 4. Which solution should be saved if you suspect you have ions from Group II – Group IV?