Practical Inorganic Chemistry-I (CHM 211) Past Paper PDF

University of Khartoum / Faculty of Science / Department of Chemistry Practical Inorganic Chemistry-I (CHM 211) 1 Practical Inorganic Chemistry-I (CHM 211) University of Khartoum / Faculty of Science / Department of Chemistry...

University of Khartoum / Faculty of Science / Department of Chemistry Practical Inorganic Chemistry-I (CHM 211) 1 Practical Inorganic Chemistry-I (CHM 211) University of Khartoum / Faculty of Science / Department of Chemistry Instructions: 1. Chemistry, and science in general, depends a great deal on the observational skill of its practitioners. Therefore, cultivate the habit of recording your observations honestly and in detail, irrespective of what may be given in the scheme (in spite of all efforts, the scheme may not be totally devoid of errors). This may save you time in case you make wrong conclusions or, hopefully, provide new information valuable to science. It will also help improve your own knowledge of the subject. 2. Maintain your observation books and fair records neatly, with appropriately numbered and dated entries. The condition of the records reflects the personality of the student and will influence his internal assessment marks. You must have your observation books during all laboratory sessions. Get them attested by the instructor after completing each experiment. 3. Maintain strict discipline inside the laboratory and concentrate on your work. Discipline is necessary for safety and helps reduce breakage. Remember, your performance is being continuously assessed. 4. Write down the procedure for the test and decide what to do before doing it. Record your observations as soon as they are made while the impressions are still fresh in your memory, and not later. Nobody has a perfect memory. Marks are awarded by the examiners based on what you have recorded and not on what you thought. Whenever you come for discussions, clarifications or reporting results, recorded observations up to that point must be presented. 5. All tests should be done systematically in the given order since the order in which the tests are done is very important. 2 Practical Inorganic Chemistry-I (CHM 211) University of Khartoum / Faculty of Science / Department of Chemistry 6. Tests for ammonium ion should be done using the original solution before any group tests. This is because ammonium chloride and hydroxide are added during group separation; so ammonium ions will always be present in the later stages of analysis. 7. Groups are identified by the formation of a precipitate on adding the reagents for that group. The color of the precipitate may provide a hint about the identity of the cation and therefore should be noted. i.e., instead of recording the observation simply as ―a precipitate is formed‖, write ―a white precipitate is formed‖ or ―a green precipitate is formed‖ etc. 8. In each group, precipitation must be completed by adding excess of the group reagent. Add the reagent drop by drop with shaking, till excess. The precipitate must be completely removed by centrifugation and the centrifugate concentrated to half its volume before proceeding to the next group. This is because each addition of group reagent will dilute the original solution. 9. The precipitate should be washed well as recommended before proceeding with confirmatory tests. The precipitate can be washed in the centrifuge tube itself by stirring thoroughly with the wash liquid, centrifuging again and discarding the supernatant. 10. When testing for a subsequent group, ions of all previous groups must be totally absent in the mixture. Therefore, if you have gone wrong and must repeat the tests with fresh mixture, you have to start from the beginning each time; analysis cannot be continued from the point of mistake. 11. Using 1 cm3 of the given mixture, carry out the group tests alone to identify which groups are present. Only the reagents for groups which are present needs to be added to the bulk of the mixture, thus saving time and reagents. Conduct the analysis using half of the 3 Practical Inorganic Chemistry-I (CHM 211) University of Khartoum / Faculty of Science / Department of Chemistry mixture given to you, reserving the other half in case you go wrong. Using too little of the mixture will not give sufficient precipitate for identification and confirmatory tests. About 5 cm3 of the mixture should be sufficient for complete analysis. 12. After each test, also note down the chemistry of the reaction or the specific nature that helped identification of the cation. This will fetch you more marks, create a favourable impression, help you during the viva voce examination and improve your understanding of chemistry. 13. Use only distilled water for dilution and washing in all tests 4 Practical Inorganic Chemistry-I (CHM 211) University of Khartoum / Faculty of Science / Department of Chemistry The group of metals For the purpose of qualitative analysis, it has been found convenient to divide the metals into six groups. The members belonging to each group together with the group precipitant are as follows: Group 1: Lead, Silver, Mercury (ous). Group reagent, HCl. Group 2: Subdivision A. Mercury (ic), Lead, Bismuth, Copper, Cadmium. Sulfides are insoluble in ammonium polysulfide. Subdivision B. Arsenic, Antimony, Tin. Sulfides are soluble in ammonium polysulfide. Group reagent Hydrogen Sulfide with HCl solution Group 3: Iron, Aluminum, Chromium Group regent. Ammonium hydroxide in the presence of ammonium chloride Group 4. Cobalt, Nickel, Manganese, Zinc. Group reagent ammonium sulfide. Group 5. Barium, Strontium, Calcium. Group reagent. Ammonium carbonate Group 6 Magnesium, Sodium, Potassium, Ammonium Soluble group 5 Practical Inorganic Chemistry-I (CHM 211) University of Khartoum / Faculty of Science / Department of Chemistry CATION GROUPS AND REAGENTS Group Group Reagent Cations (some metals as more stable oxy anions) Group I Dil. HCl (2M) Hg+, Ag+, Pb2+ Group II Dil. HCl + H2S gas Hg2+, Pb2+, Bi3+, Cu2+, Cd2+. As3+, Sb3+, Sn2+, Sn4 Group III NH4Cl + NH4OH solutions (2M) Al3+, Cr3+, Fe2+, Fe3+, Mn3+ Group IV NH4Cl + NH4OH+ H2S gas Co2+, Ni2+, Mn2+, Zn2+. Group V NH4Cl + NH4OH + (NH4)2CO3 solutions (2M) Ca2+, Sr2+, Ba2+. Group VI No common reagent NH4+, Mg2+, Na+, K+ Preliminary test: 1. Heat in a Dry Tube. Place a small quantity (10 mg) of the solid substance in a dry, hard glass ignition tube (2 in, *1/2 in.) Hold the tube nearly horizontally and heat it gradually and carefully over a naked flame. Look for the color changes, sublimation, the condensation of moisture in the cool part of the tube and the evolution of gases. 2. Treatment with water. 6 Practical Inorganic Chemistry-I (CHM 211) University of Khartoum / Faculty of Science / Department of Chemistry Add about 5 mg of the solid material to test tube half full of water, place the tube in the heating block and heat just to boiling. Test solution with litmus paper. An alkaline solution may result, either from the solution of certain metallic hydroxides or from the hydrolysis of salts of strong bases and weak acids. An acid reaction indicates either the presence of an acid, or it may be the result of hydrolysis of salts of strong acids and weak bases. 3. Treatment with dilute hydrochloric acid. Fill a test-tube one third full of dilute hydrochloric acid and heat to boiling in the heating block. Remove the tube from the black and stand it in the rack. To the hot acid add about 5 mg of the material and observe any reaction. If gases are evolved note their color and smell and try to identify them. 4. Treatment with Concentrated sulfuric Acid Place ten drops of concentrated sulfuric acid in a test tube, add no more than 5 mg of test material and cautiously shake the tube. Observe any reaction, noting the color of any gases evolved. Carefully warm the contents of the tube but do not heat strongly, again watch for any reaction. Gently shake the tube and look for non-wetting of the inside of the tube by the liquid, i.e., a behavior as though the tube were covered with oil. 7 Practical Inorganic Chemistry-I (CHM 211) University of Khartoum / Faculty of Science / Department of Chemistry 5. Test for a Borate. Using a pipette place five drops of concentrated sulfuric acid into the crucible, add about 10 mg of solid calcium fluoride and 5 mg of the solid test material. And stir into apaste. Cover the paste with a little methyl alcohol and light it, talking care to remove the bottle of alcohol first. If the flame burns with a green edge, or has a green over mantle, then a borate is confirmed. The presence in the test of an excess of calcium or other fluoride is necessary to suppress interference from copper and barium should they happen to be present in the analysis. Methylated spirits can be substituted for methyl alcohol but if this is done then the greenmantle does not appear until the flame is dying. 6. Test for Ammonium salts Into the boiling tube place about 10 mg of the solid material, half fill the tube with dilute caustic soda solution, place the tube in the heating block and bring the contents boiling. Remove the tube and test the vapor for ammonia by (a) Smell, (b) a drop of concentrated hydrochloric acid carried in the pipette to the mouth of the tube ( copio(copiousfumes evolved ) and ( c) a place of filter paper socked in mercurous nitrated solution ( blackened). Continue boiling for some thirty seconds and test again- this is necessary in order to release ammonia from certain double salts, e.g. ferrous ammonium sulfate. 8 Practical Inorganic Chemistry-I (CHM 211) University of Khartoum / Faculty of Science / Department of Chemistry 7. Test for Nitrate or Nitrite. This is carries out on the solution from test 6. If ammonia has been evolved, boiling must be continued until its presence is no longer indicated by testing. The ammonia-free solution is then cooled, about 5 mg of Devarda s allay added the whole gently warmed until the gas production starts. The tube is removed from the heating block and the gas again tested for ammonia- its presence indicated a nitrate or nitrite. 8. Test for a Chromate. Since nearly all chromates are readily soluble in dilute mineral acids the following test need only to be done when the substance gives a colorless solution with dilute hydrochloric acid in test 3 above. Half fill a test tube with dilute hydrochloric acid, add two drops of hydrogen peroxide solution followed by sufficient ether to give a layer about half of the inch deep above the acid. Drop into the tube about 5 mg of the solid test material and immediately shake the contents. The separation of blue ethereal layer confirms destruction of a chromate by reducing agents that may be present in the analysis is substantially avoided. 9 Practical Inorganic Chemistry-I (CHM 211) University of Khartoum / Faculty of Science / Department of Chemistry 9. Test for a Carbonate. The success of any carbonate test depending on the evolution and detection of carbon dioxide turns on the expulsion of the gas dissolved in the reacting liquid. This can only be raising the temperature of the reaction to above 60 ℃. To this end the following technique offers a very simple solution to former troubles. One third fill a test tube with dilute hydrochloric acid. Place the tube in its appropriate hole in the heating block and bring its contents just to boiling; then remove it and put it in the rack. Immediately, drop into the hot acid a small amount of the test material. Squeeze the test of the pipette to expel air, then lower the up into the test atmosphere, to within half an inch of the surface of the liquid. Now release the teast and suck into the pipette some of the test atmosphere. Remove the pipette, insert the tip of it under the surface of little lime water to held in another test tube and, by gentle pressure on teast, slowly bubble the gas from the pipette through the lime water. Milkiness denotes the presence of carbon dioxide. 10 Practical Inorganic Chemistry-I (CHM 211) University of Khartoum / Faculty of Science / Department of Chemistry Preparation of solution Put into the boiling tube about 5 mg off the solid material and cover it with 8 drops of concentrated hydrochloric acid and 8 drops of bromine water. Boil until excess of bromine is removed. Add 2 drops of a 1 % solution of hydroxylamine hydrochloride (NH2OH.HCl), boil and centrifuge. Treat any residue as insoluble. Separation of Group II Put into the boiling tube the prepared solution. Place the tube in the heating block and bring it contents to boiling. Immediately pass through it a fast stream of H2S gas for 10- 15 sec. boil and repass a little more gas. Add an equal volume of water and boil off surplus H2S. Now add a volume of 2M NH4OH equal to the volume of liquid in the tube. Mix through add check that solution is only just acid (blue) to Congo red paper. Pass through a stream of H2S. Centrifuge and wash ppt 11 Practical Inorganic Chemistry-I (CHM 211) University of Khartoum / Faculty of Science / Department of Chemistry Group IIA (Copper Group) Precipitate (HgS, PbS, Bi2S3, CuS, CdS, Ag2S, As2S3, Sb2S2, SnS2). Half fill the tube containing the ppt. with lithium hydroxide reagent and heat just to boiling. Centrifuge. Solution (Thio compounds of As, Sb and Sn). Add a little dil. HCl Residue: ( HgS, PbS, Bi2S3, CuS, CdS, Ag2S ( Warm with a little HNO3 (1+1). until the solution is just acidic to Congo red; pass H2S and warm. If Dilute and centrifuge no ppt., As, Sb, Sn are Absent discard the solution. If a ppt – centrifuge and discard solution. Wash the ppt by boiling with a dil.. Residue: Solution: (Pb, Bi, Cu or Cd and Ag nitrates). Place the beaker, add 5 drops of conc.H2SO4 and solution of NH4Cl. Centrifuge and discard washing. Cover the Black – evaporate to fumes of SO3. residue with 10 drops of conc. HCl, heat just to boiling and Cool, dilute and centrifuge. centrifuge. HgS. Dissolve by Placen boiling with Residue. Solution (SnCl2, SnCl4) Boil vigeroulsy, then Residue Solution (Cu, Cd, Bi, Ag sulphates). Add NH4OH(1+1) until solution smells conc. HCl (WhitePbSO4). Yellow add 5 drops pf water. Cool, pass H2S and strongly of ammonia. Warm and centrifuge and bromine Dissolve in a As2S2 centrifuge. water. conc. solution confirms Boil off Br2 of ARSENIC and Precipitat Solution (Cu, Cd, Ag amines). Add 1 drops of KI solution. Ammonium Warm and centrifuge Precipitate. Solution. Place in the dilute. acetate. e (white Orange Sb2S2 Bi(OH)3). beaker, boil off H2S. Add Add 2 drops Add 2 drops of confirms Add dil. to the gently boiling of SnCl2 K2CrO4 HNO3 and Precipitate Solution divide into two parts ANTIMONY solution dilute NH4OH Solution. yellow Color 2 drops of 1.Add 2 drops K4Fe(CN6) solution Acream ppt. drop by drop solution until A white ppt ppt confirms thiourea. and acidity with acetic acid. A LEAD A yellow Of AgI reddish-brown ppt. confirms only weakly acid to Congo turning grey ppt. confirms COPPER Red paper. Awhite or confirms confirms SILVER 2.Add a little solid Na2S2O4 and boil. cream ppt confirm TIN MERCURY Bismuth Remove any ppt. and pass H2S. A yellow ppt. confirms CADMIUM Or add 3 drops of KCN solution and pass H2S A yellow ppt confirms CADMIUM 12 Practical Inorganic Chemistry-I (CHM 211) University of Khartoum / Faculty of Science / Department of Chemistry SEPARATION OF GROUP III Solution. After of the removal of precipitated sulphides from group II put the solution in the beaker and boil off H2S (test for complete removal with a piece of l acetate paper). Add two drops of conc. HNO3 and boil. (Withdraw 3 drops and test for a phosphate (add 1 drop of conc. HNO3, 3 drops of ammonium molybd reagent and warm: a bright yellow ppt denotes a phosphate). If present, this and other interfering acid radicals such as fluoride, silicates and borates, must be remo by special procedure before continuing with the analysis. If absent, or after removal, add 3 drops of a saturated solution of NH4Cl and boil. To the gently boi solution add NH4OH (1+1) drop by drop, until the solution is just neutral to litmus. Centrifuge and wash the ppt. Precipitate: Fe (OH)3, Al(OH)3, Cr(OH)3,MnO(OH)). Cover with water, add a little solid Na2O2 and heat until effectiveness ceases. Centrifuges. : Residue (Fe(OH)3, MnO(OH. Solution (Na2CrO4, NaAlO2). Acidify with dil. HCl and divide into two parts Dissolve in dil. HNO3 and divide into two parts- 1. Add 1 drop of alizarin S solution followed by dil. NH4OH until just alkaline. Warm. Acidity with acetic acid. 1. Add dil. HNO3 and a little solid A red lake confirms NaBiO3. Shake. A purple color ALUMNIUM confirms 2. A yellow color suggests a chromate. Manganese Add a little ether followed by 2 drops of H2O2 Shake. A blue color in the ether layer confirms 2. Add 2 drops of a solution of CHROMIUM K4Fe(CN)3. A deep blue color confirms IRON (Test original substance for initial state of oxidation) 13 Practical Inorganic Chemistry-I (CHM 211) University of Khartoum / Faculty of Science / Department of Chemistry REMOVAL OF INTERFERING ANIONS Removal of interfering anions Excluding Phosphate. After the removal of H2S followed by oxidation with HNO3, add 5 drops of conc. H2SO4 to the solution in the beaker and evaporate, on the heating block, to fumes of SO3. Cool. Dilute and centrifuge. Residue: Black (BaSO4, SrSO4, CaSO4, SiO3). Transfer to piece of nickel foil, dry and Centrifugate: Add 1 drop of conc. HNO3 followed by NH4Cl and NH4OH fuse with one-quarter of pellet of NaOH. Cool and leach in a 5 % solution of NaCO3. to precipitate group III Boil and centrifuge. Solution. Examine for Residue (BaSO4, SrSO4, CaSO4). Dissolve in dilute acetic acid and silicate examine for group V 14 Practical Inorganic Chemistry-I (CHM 211) University of Khartoum / Faculty of Science / Department of Chemistry SEPARATION OF GROUP IV Solution. Pass a steady steam of H2S gas into the solution after the removal if Group III hydroxides. Warm and centrifuges Precipitate (CoS, NiS, MnS, ZnS). Cover with water, add 3 drops of cold, dil. HCl, shake and centrifuge. Residue: (CoS, NiS). Solution (MnCl2, ZnCl2). Boil off H2S. add 2 drops of bromine water and a pellet of NaOH. Warm and centrifuge. Dissolve in dil. HCl and bromine water. Boil off excess bromine. Add 1 drop of hydroxylamine. Divide into two parts: Precipitate: Solution: pass a steady stream of H2S gas through the solution. 1. Add one drop of SnCl2 solution, a little Amy Dissolve in dil. HNO3. Add solid NaBiO3. Shake A white ppt. of ZnS confirms alcohol and a few crystals of KCNS. Shake. A A purple color confirms ZINC blue color in the alcohol layer confirms MANGANESE COBALT 2. Add 2drops of a solution of dimethylglyoxime followed by NH4OH (1+1) until alkaline. A pink ppt. insoluble in acetic acid confirms NICKEL 15 Practical Inorganic Chemistry-I (CHM 211) University of Khartoum / Faculty of Science / Department of Chemistry REMOVAL OF INTERFERING ANIONS Removal of interfering anions including Phosphate. After boiling off H2S from group II and oxidation with conc. HNO3, add to the solution in the beaker 2 drops of a 5% solution of ZrOCl2 and 2 drops of a saturated solution if NH4Cl. Bring to boiling and add 5 drops of 1 % solution of tannin followed by dropwise addition of dilute NH4OH to the gentle boiling solution until it is faintly acid ( just blue) to a piece of Cong Red paper. Digest hot, centrifuge and discard the precipitate. Add 3 drops of conc. HNO3 and 5 drops of conc. H2SO4 to the solution held in the beaker and evaporate on the heating block to fumes of SO3. Cool, dilute and centrifuge. Residue: Black (BaSO4, SrSO4, CaSO4, SiO3). Transfer to piece of nickel foil, dry and Solution: Add 1 drop of conc. HNO3 followed by NH4Cl and NH4OH to fuse with solid NaOH. Cool and leach in a 5 % solution of NaCO3. Boil and centrifuge. precipitate group III Examine the solution for silicate and dissolve the residue in dil. Acetic acid. Examine acetic acid solution for group V 16 Practical Inorganic Chemistry-I (CHM 211) University of Khartoum / Faculty of Science / Department of Chemistry SEPARATION OF GROUP V Solution. After removal of group IV sulphides, add to the solution 2 drops of dilute ammonia and 3 drops of a solution of (NH4)2CO3. Bring to boiling and allow to stand hot for a short time. Centrifuge. Precipitate (BaCO3, SrCO3, CaCO3). Dissolve in dil. Acetic acid, boil off CO2, add 1 drop of K2CrO4 solution. Allow to stand. Centrifuge Precipitate. Yellow BaCrO4 confirms Solution. Add 3 drops of a saturated solution of (NH4)2SO4. Warm and allow to stand. Centrifuge. BARIUM Precipitate. White SrSO4 confirms STRONTIUM Solution. Add 2 drops of a solution of ammonium oxalate. A white ppt. confirms CALCIUM 17 Practical Inorganic Chemistry-I (CHM 211) University of Khartoum / Faculty of Science / Department of Chemistry SEPARATION OF GROUP VI Solution. After removing the precipitated carbonates of group V place the solution in the crucible and evaporate to dryness. Transfer to the fume cupboard and heat the residue until all white fumes have ceased to come off, that is until all ammonium salts have been sublimed. Cool, dissolve any residue in very dilute acetic acid and divide the solution into three parts. 1. Add one drop of Magneson reagent and three drops of caustic soda solution. Warm. A blue lake confirms Magnesium 2. Add 2 drops of dilute acetic acid and a little solid sodium cobaltinitrite. A yellow precipitate confirms Potassium 3. Add several drops of a solution of nickel uranyl acetate. Shake and allow to stand. A greenish yellow, crystalline precipitate confirms Sodium 18 Practical Inorganic Chemistry-I (CHM 211) University of Khartoum / Faculty of Science / Department of Chemistry 19 Practical Inorganic Chemistry-I (CHM 211) University of Khartoum / Faculty of Science / Department of Chemistry Chemical reactions involved in the basic radicals Ammonium salt equation: Ammonium (NH4+) NH4+ + NaOH →Na+ + H2O + NH3 ↑ NH3 + HCl →NH4Cl (white fumes) Group II equations Mn+(aq) + n H2S(g) = M2Sn (s) + 2nH # Hg2+ HgS + 2HCl Br2/H2O HgCl2+ 2H+ ∆ HgCl2 + SnCl2(aq) Hg2Cl2(s) + SnCl4(aq) Hg2Cl2 + SnCl2(aq) Hg + SnCl4(aq) grey ppt M2Sn(s) + nHNO3 M(NO3)n(aq) + nH2S(g) ( M is either Pb or Bi or Ag+ or Cu2+ or Cd2+) 2+ 3+ # Pb2+ Pb(NO3)2 + H2SO4 PbSO4 + 2HNO3(aq) PbSO4 + K2CrO4 PbCrO4 + K2SO4 Yellow ppt M(NO3)n(aq) + n H2SO4 M2(SO4)n(aq) + 2n HNO3 ( M is Bi3+ or Ag+ or Cu2+ or Cd2+) # Bi3+ Bi2(SO4)3(aq) + NH4OH Bi(OH)3 + (NH4)2SO4 White ppt Bi(OH)3 + SC(NH2)2 HNO3 [Bi(SC(NH2))2]3+ thiourea Yellow complex ion # Ag+ Ag2SO4 + NH4OH [Ag(NH3)2]+ 2SO4 (aq) 20 Practical Inorganic Chemistry-I (CHM 211) University of Khartoum / Faculty of Science / Department of Chemistry [Ag(NH3)2]+ 2SO4 (aq) + 2KI 2AgI + K2SO4 + NH3 (g) # Cu2+ CuSO4(aq)+ NH4OH [Cu(NH3)4]SO4(aq) Cu(NH3)4]SO4(aq) + K4[Fe(CN)6] HNO3 Cu2[Fe(CN)6] Red-brown ppt # Cd2+ CdSO4(aq) + NH4OH [Cd(NH3)4]SO4(aq) [Cd(NH3)4]SO4(aq) + H2S KCN CdS Yellow ppt. Group (III): (Al3+, Cr3+, Fe2+, Fe3+ and Mn3+) M3+(aq) + NH4OH NH4Cl M(OH)2 + NH4+ Gelatinous ppt. # Mn3+ MnO(OH) + 5NaBiO3 + 14 HNO3 2MnO4- + 5Bi3+ + 7H2O Violet color # Fe3+ 4Fe3+(aq) + K4[Fe(CN)6] Fe4[Fe(CN)6]3 + 4K+ Prussian blue # Cr3+ Cr(OH)3 + Na2O2 Na2CrO4 (aq) Na2CrO4 (aq) H+ Na2Cr2O7 Na2Cr2O7 + H2O2 ether blue ether layer 21 Practical Inorganic Chemistry-I (CHM 211) University of Khartoum / Faculty of Science / Department of Chemistry # Al3+ Al(OH)3 + Na2O2 2NaAlO2 + 2H2O NaAlO2(aq) + HCl Al(OH)3 (aq) Group (IV) : ( Co2+, No2+, Zn2+ and Mn2+ ) M2+(aq) + H2S NH4OH/NH4Cl MS + 2H+ # Co2+ Co2+(aq) + 4SCN- amyl alcohol [Co(SCN)4-]2- Blue alcohol layer # Ni2+ 22 Practical Inorganic Chemistry-I (CHM 211) University of Khartoum / Faculty of Science / Department of Chemistry # Mn2+ Mn2+(aq) + NaBiO3 MnO4- + Bi3+ + Na+ Zn2+(aq) + H2S ZnS + 2H+ White ppt Group (V): ( Ca2+, Ba2+ and Sr2+) Mn2+ (aq) + (NH4)2CO3 MCO3 + 2NH4+ # Ba2+ Ba2+(aq) + K2CrO4 BaCrO4 + 2K+ Yellow ppt # Sr2+ Sr2+(aq) + (NH4)2SO4 SrSO4 + 2NH4+ # Ca2+ Ca2+(aq) + (NH4)2SO4 (NH4)2Ca(SO4)2 (aq) (NH4)2Ca(SO4)2 + (NH4)2C2O4 CaC2O4 + 2(NH4)2SO4 Groyp (VI): (Mg2+, Na+ and K+) # Mg2+ 23 Practical Inorganic Chemistry-I (CHM 211)  University of Khartoum / Faculty of Science / Department of Chemistry Mg2+(aq) + Na2HPO4 NH4OH /NH4Cl MgHPO4 + H2O # K+ K+(aq) + Na3[Co(NO2)6] K2Na[Co(NO2)6] + 2 Na+ # Na+ Na+(aq) + Ni(OAC)2UO2(OAC)2 Na(UO2)3(OAC)9.9H2O Nickel yournyl yellow ppt Last update Jan. 2023 24 Practical Inorganic Chemistry-I (CHM 211)