E-StoreQUICK REVISION-AIEEE - Practical CHEMISTRY
The salt analysis given below is strictly according to AIEEE . Just go through it quickly in 15 mts you will learn about practical portion related to Salt analysis. The radicals which are not in sylabus not given in the text
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Tests For Cations Zero NH4+ NaOH and Nessler’s Reagent Brown Precipitate I Group Pb2+ Salt Solution and dil. HCl White Precpitate II Group Pb2+ Cu2+ Cd2+ Salt Solution , dil HCl and H2S Black Precipitate Black Precipitate Yellow Precipitate III Group Al3+ Fe3+ Mn2+ Salt solution is treated with NH4Cl solid followed by NH4OH Gelatinous White ppt. Gelatinous Brown ppt. White turning Brown on standing. IV Group Mn2+ Zn2+ Ni2+ Salt solution is treated with NH4Cl solid followed NH4OH and H2S. Buff or Pale pink ppt Dull white ppt Black ppt V Group Ba2+ Ca2+ Salt solutions is treated with NH4Cl followed byNH4OH and (NH4)2CO3 White ppt White ppt VI Group Mg2+ Salt solutions is treated with NH4Cl followed byNH4OH and (NH4)2HPO4 White ppt Preparation of Original Solution . The mixture should be dissolved in an suitable solvent. The choice of solvents can have the following sequence.1.Cold Water, 2. Warm water, 3. Dilute HCl, 4. Concentrated HCl, 5. Dilute HNO3, 6. Concentrated HNO3, and 6. Aquaregia. The solution prepared by dissolving the mixture in the solvent is referred to a the original solution or O.S. EXPERIMENT OBSERVATION INFERENCE 0 Group Shake the aqueous mixture solution well with NaOH and note the odour. Smell of Ammonia NH3 Presence of NH4+ indicated To one ml of Nesslers (K2[HgI4]) reagent add aqueous mixture solution Brown precipitate of Mercuric Amido Iodide (NH2.HgO.HgI) is obtained. NH4+ Confirmed I Group A) White Precipitate. Dissolve the above precipitate in hot water and perform the following tests The white ppt. of PbCl2 is soluble in hot water Pb2+ + 2Cl-® PbCl2 Pb2+ may be present (i) Treat a part of the above solution with K2CrO4 solution Yellow precipitate due to the formation of PbCrO4. Pb2+ + CrO4® PbCrO4. Pb2+ Present (ii) To another part of group one solution add KI solution Yellow precipitate due to the formation of PbI2 which is soluble in hot water reappears as golden spangles on cooling Pb2+ + I-® PbI2 Pb2+ Confirmed II Group Black Precipitate.(NiS). Dissolve the group II black residue in dil HNO3 and perform the following tests. a) If the solution is blue perform the following tests. (i) Add NH4OH drop wise until it is in excess. Blue precipitate is formed which dissolves in excess of the reagent. Cu2+ + 2OH-® Cu(OH)2 Cu(OH)2 + 4NH4OH ® [Cu(NH3)4](OH)2 + 4H2O. Cu2+ (ii) Acidify the second portion with acetic acid and add potassium Ferrocyanide. Reddish brown precipitate is obtained. 2Cu2+ + [Fe(CN)6]4-® Cu2[Fe(CN)6] Cu2+ b) If the solution is colour less perform the following tests. (i) Add KI to one part of the above solution. Yellow precipitate due to the formation of PbI2 which is soluble in hot water reappears as golden spangles on cooling. Pb2+ + 2I-® PbI2 Pb2+ Confirmed (ii)Add K2CrO4 to another part of the solution Yellow precipitate due to the formation of PbCrO4 Pb2+ + CrO42-® PbCrO4 Pb2+ Confirmed III Group Dissolve the white gelatinous precipitate by boiling with NaOH solution and divide it into two parts. (i) To the first part add NH4Cl and boil White precipitate Al3+ present (ii) To the second part add dil. HCl ,litmus solution and excess of NH4OH A blue lake Presence of Al3+ confirmed. Ash test: Group III residue + 3 drops of conc. HNO3 + 3 drops of Cobalt nitrate. Dip a rolled filter paper in this solution and burn in the flame A Blue tinted ash is obtained. 2Al(OH)3 ® Al2O3 + 3H2O. 2 Al2O3 + 2Co(NO)3 ® 2CoO.Al2O3 + 4NO2 + O2 Presence of Al3+ confirmed. B) Gelatinous brown ppt. Fe(OH)3. Dissolve the ppt. in dil HCl and divide it into two parts. (i) To one part of the above precipitate add Potassium Ferrocyanide solution. A blue (Prussian blue) coloured solution or precipitate is formed. Fe3++ 3 [Fe(CN)6]4-® Fe4[Fe(CN)6]3 Presence of Fe3+ indicated. (ii) To the second part add Potassium thiocyanide. Blood red coloration Fe3+ + 3CNS-® Fe(CNS)3 Presence of Fe3+ confirmed. IV Group A) Black precipitate. (NiS) Conformation for Ni2+ Dissolve the black precipitate in dil. HCl add NH4Cl and NH4OH and divide into two parts: Presence of Ni2+ (i) To the first part add Dimethyl Glyoxime Rose Red Precipitate. Presence of Ni2+ Confirmed. (ii) Through the second part pass H2S gas. A black precipitate is formed Presence of Ni2+ Confirmed. B)DullWhite precipitate. Conformation for Zn2+ Dissolve the white ppt. in dilute HCl, to this solution NaOH is first added in drops then in excess until the ppt. dissolves. (i) To one part add Acetic acid and potassium Ferrocyanide. White precipitate is formed. Zn2+ + [Fe(CN)6]4-® Zn2[Fe(CN)6] Presence of Zn2+ confirmed. (ii) Pass H2S and filter White precipitate is formed Presence of Zn2+ confirmed. Ash test: Group IV residue + 3 drops of conc. HNO3 + 3 drops of Cobalt nitrate. Dip a rolled filter paper in this solution and burn it in the non luminous part of the flame. Green tinted ash is formed. Presence of Zn2+ confirmed C) Conformation of Mn2+. Buff precipitate is heated with PbO2 and conc. HNO3 and dilute with water. The supernatent liquid turns pink due to the formation of permanganic acid. 2Mn(NO3)2 + 5PbO + 6HNO3 ® 5Pb(NO3)2 + 2HMnO4 + 2H2O Presence of Mn2+ is confirmed. V Group White precipitate: Dissolve the group V precipitate in minimum quantity of Acetic acid and divide into three parts. Keep aside a part of the group precipitate for Flame test. A Yellow precipitate is formed. Ba2+ + CrO42-® BaCrO4 Presence of Ba2+ Ba2+ confirmed. · To the third part add Ammonium Oxalate A White precipitate is formed. Ca2+ + C2O42-® Ca C2O4 Presence of Ca2+ confirmed Flame test: The group V residue is treated with conc. HCl and a Nichrome / Platinum wire dipped in the above solution is shown into the non luminous part of the flame. a) Apple Green flame b) Brick Red Flame a) Ba2+ Confirmed b) Ca 2+ confirmed VI Group White Crystalline ppt. Group VI ppt. is dissolved in minimum quantity of dil HNO3 and few drops of conc. HNO3 and Cobalt Nitrate are added. A rolled filter paper is dipped in the above solution and burned in the non luminous part of the flame. A pink tinted ash is obtained. Presence of Mg2+ is confirmed. Magneson reagent test: The group VI residue is dissolved in dil. HCl to this a few drops of Magneson reagent is added followed by NaOH. A blue precipitate is formed. Presence of Mg2+ is confirmed
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