+-: Zn, Ag, Al -: K, Na, NH4 => verify through flame test DAY 10: Solutions Color of Gas Odor of Gas Formula of Gas Test for Gas ObservationsNa2CO3 + H2SO4 Colorless Vinegar-like CO2 Loss of precipitatesNa2SO3 + H2SO4 Colorless Mabaho H2SO3 Paper with K2Cr2O7 turns from orange to light green Na2S + H2SO4 Colorless Rubber-like H2S Faint orange to white Pb(CH3COO)2Na2S2O3 + H2SO4 Colorless Gunpowder-like S2O3 Green-ishNaNO2 + H2SO4 Colorless Water-like NO2 Loss of precipitates DAY 11: Solution +BaCl2 +3M HCl + KMnO4 ( ) ( ) Na2SO4 - ( ) Na2SO3 + ++ ( ) Na2CO3 + +- Purple ( ) Na3PO4 + +- Purple ( ) Na2CrO4 + (yellow) +- Red ( ) NaF + (white) ++ ( ) Na2Cr2O7 + (orange) +- Dark Red ( ) NaNO2 - - ( ) Na2S + ++ ( ) Na2S2O3 + ++
( )Confirmatory Tests for CationsAg+: Add 5 drops 3M HCl to 10 drops unknown => Centrifuge and decant => Treat the ppt withseparate 2mL portions of hot water (twice), shaking the test tube while the test tube is heatedin the water bath. Decant the first 2mL portion of hot water and treat the precipitate with thesecond 2mL portion of hot water. => Centrifuge and decant => Add 1mL 6M NH3 to theprecipitate and stir, => Add 6M HNO3 until acidic. White ppt confirms Ag+.Fe3+, Ni2+: Add 5 drops 3M NaOH to 10 drops unknown => Centrifuge and decant. => Add thewater to the precipitate and discard the washing. Add enough water to give a total volume ofabout 1 mL. Stir. => Divide the solution into two equal portions. => (1)Add 3 drops of 1M KSCN.A deep red color confirms the presence of Fe3+. => (2) Add 6M NH3 dropwise until the solution isbasic to litmus. Add 5 drops of dimethyglyoxime [(CH3)2C2(NOH)2] solution and stir. Formation ofa bright red precipitate confirms the presence of Ni2+.Zn2+: (1)Add 5 drops 3M NaOH to 10 drops unknown. Centrifuge and decant. To the hydroxide ofzinc, acid 6M NH3 drop by drop with stirring until it dissolves. Then add 2 drops of thioacetamidesolution. Stir and heat in water bath for 3 minutes. Formation of a white precipitate, whichdissolves, when the solution is acidified, confirms the presence of Zn2+. (2)To a fresh sample ofunknown solution, add 10 drops of thioacetamide solution, stir and heat in the water bath for 3minutes. Formation of white precipitate, which dissolves when the solution is acidified with 6MHCl, confirms the presence of Zn2+.Cu2+: Add concentrated NH3 dropwise to the unknown solution until the solution is distinctlybasic. A deep blue solution confirms the presence of Cu2+.Ca2+: To the unknown solution, add 6 drops of H2O and concentrated CH3COOH dropwise. Thenadd 6 drops of 1M (NH4)2C2O4 and stir and heat in the water bath. The presence of a whiteprecipitate confirms the presence of Ca2+.Mg2+: To the unknown solution, add 6M NH3 until basic. Then add a small amount of dibasicammonium phosphate (NH4)2HPO4 until Mg2+ precipitate as a white MgNH4HPO4 · 6H2O. If theprecipitate dissolves in 6M CH3COOH, then the unknown contains Mg2+.Al3+: Add 2 drops of aluminon reagent (C22H23O9N23) to the unknown solution. Add 3-5 drops of6M NH3 o make the solution just basic. Mix this and let it stand. A flocculent precipitate coloreda characteristic of red by the dye proves the presence of Al3+. If color and precipitate areindefinite, make the solution acid with 3M HCl, then basic with NH3, to build up the NH4+concentration so that the solution becomes less basic.Confirmatory Tests for AnionsCO32-, SO32-, PO42-: Add 5 drops of BaCl2 to 10 drops unknown => Centrifuge and decant => Add1mL of 3M acetic acid dropwise to the solid. Stir. Add 2 more drops of 3M CH3COOH. Stir, if
bubbles are observed, continue to add 3M CH3COOH until no bubbles are noted. This destroysthe CO32- Test for CO2 gas. => Divide the solution into 2 portions => (1) Add: 5 drops of 6M HCl, 5drops of 0.5M Ba(CH3COO)2 or Ca(CH3COO)2, 5 drops of 3% H2O2. Formation of a whiteprecipitate confirms presence of SO32-. => (2) Add: 5 drops of concentrated HNO3, 5 drops ofammonium molybdate solution. Heat in water bath for 1 minute. Formation of yellowprecipitate confirms the presence of PO43-.SO42-, CrO42-: Add 5 drops of BaCl2 to 10 drops unknown => Centrifuge and decant => Washprecipitate with 1mL water. Discard washings. Add 10 drops of 3M HCl and stir. If solubleproceed to (2). If not, proceed to (1) => (1) Add BaSO4. Add 10 drops of H2O and 5 dropsconcentrated HCl and stir. White precipitate confirms SO42-. => (2) If soluble, BaCrO4. Add 6MNH3. Yellow precipitate confirms CrO42-.Cl-, Br-, I-, CNS-: Add 5 drops AgNO3 to 10 drops unknown => Centrifuge and decant => AgCl(White/Dirty White), AgBr (Cream/Light Yellow), AgI (Yellow), AgCNS(White) => Add 2-6 drops6M NH3. If soluble, add 3M HNO3. Stir until the solution is acidic (Check with litmus paper).Formation of white precipitate confirms the presence of Cl-. If insoluble proceed to next step =>Divide precipitate into two. => (1) Place a very small amount of solid on a watch glass. Add 2drops of 3M HCl and 1 drop of FeCl3. A red-blood solution confirms the presence of CNS-. => (2)Add 1mL of H2O to the bulk of the residue. Acidify with 6M CH3COOH. Add 1 microspatula of Zndust and stir thoroughly for 3 mins. Centrifuge. => Disregard residue. Divide solution into twoportions. => Test with litmus paper if solution is acidic. If not, acidify with a few drops of 6MCH3COOH. Add 10 drops of oil and a few crystals of NaNO2. Dilute with H2O to a volume of 2mLand shake vigorously. Did solution turn violet? If yes, I- is present. If no, proceed to next step. =>Yellowish color in oil layer confirms the presence of Br-.NO3-: (1) Place 1 drop of unknown in spot plate. Add 2 drops of concentrated H2SO4 and 1 dropof napthylamine. Wait several minutes. Development of purple color confirms the presence ofNO3-. (2) Place 5-10 drops of unknown solution in a small teest tube. Without shaking the testtube, add 5 drops of freshly prepared solution of FeSO4 and 2-3 drops concentrated H2SO4.Observe the formation of brown ring at the junction of the solution. This indicates the presenceof NO3-. (3) Place a small crystal of FeSO4 in a depression of a spot plate. Add 1 drop of unknownand 1 drop of concentrated H2SO4. Formation of a brown ring around the crystal indicates thepresence of NO3-.NO2-: (1) Add 1 micro spatula of urea to 1mL 3M HCl. Place 10 drops of this solution to 10 dropsof unknown. Evolution of gas confirms the presence of NO2-. (2) Add a freshly prepared solutionof FeSO4 to 5 drops unknown. Then, add 2 drops of concentrated H2SO4. The rapid evolution of abrown gas confirms the presence of NO2-.CH3COO-: Warm 50mg of the unknown with 2 drops ethanol and 2 drops of sulfuric acid. Thefruity odor of the product is apparent if the mixture is allowed to cool and then diluted withwater on a watch glass.
CrO42-, Cr2O72-: acidify 10 drops unknown solution with concentrated sulfuric acid. Cool. Get 2drops of this solution and mix to a solution of 1 drop 20% H2O2 and 5 drops ether. Shake. Bluecolor in the upper ethereal layer confirms the presence of CrO42- if the original solution is yellow,and Cr2O72—if the original unknown solution is orange.C2O42-, F-: acidify 10 drops of unknown solution with 3M CH3COOH. Boil. Add 10 drops of CaCl2solution. If precipitate forms, centrifuge. Wash the precipitate with hot water. Add 5 drops of1M H2SO4 and heat. White residue confirms the presence of F-. Centrifuge and decant. Add 1drop of dilute KMnO4 to the liquid. Decolorization of KMnO4 confirms the presence of C2O42-.S2-, SO32-, PO43-: Add 5 drops of AgNO3 to 10 drops of unknown. => S2-(dark brown precipitate),SO32-(white precipitate), PO43-(yellow precipitate).