lab 4 the separation and identification of a series of cations POST
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lab 4 the separation and identification of a series of cations POST

Course: CHEM 203, Fall 2009

School: University of Illinois,...

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The Separation and Identification of a Series of Cations By: Jason Hsieh Partners: Anna Wetherholt, Jung Soo Kim BB5 11/12/09 1 Abstract: This labs purpose involved identifying 10 cations with 11 other reagents and finding trends and properties that would enable one identify unknown cations for future labs. The techniques used involved using reagents such as acids, bases, acidic/basic H2S, chromates, and...

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Separation The and Identification of a Series of Cations By: Jason Hsieh Partners: Anna Wetherholt, Jung Soo Kim BB5 11/12/09 1 Abstract: This labs purpose involved identifying 10 cations with 11 other reagents and finding trends and properties that would enable one identify unknown cations for future labs. The techniques used involved using reagents such as acids, bases, acidic/basic H2S, chromates, and carbonates/phosphates, whereupon careful observations are recorded. Some noticeable trends involved how the first five ions, (lead, barium, bismuth, iron and manganese) generally formed precipitates with most reagents, whereas the other five (silver, copper, nickel zinc and aluminum) tended to form less. Also, the acids seemed to be the least reactive of the reagents and other trends were carefully noted. Introduction: This lab involved a series of reactions and tests to 10 cations in an attempt to chemically fingerprint them. The reactions included testing for amphoteric behavior (1), behavior in aqueous ammonia (2), behavior with sulfide ions (3), behavior in carbonate and phosphate solutions (4), and confirmatory tests (5). These tests are summarized as follows: 2 (1) Sn(OH)2(s) + 2H+(aq) Sn2+(aq) + H2O(l) or Sn(OH)2(s) + OH-(aq) Sn(OH)3- (aq) (2) Cu2+(aq) + 2OH-(aq) Cu(OH)2(s) and (with excess ammonia) Cu(OH)2(s) + 2NH4+(aq) + 2NH3(aq) Cu(NH3)42+(aq) + 2H2O(l) (3) M2+(aq) + S2-(aq) MS(s) and has acidic/basic properties that enable the user to control the sulfide ion concentration by shifting the equilibrium by adding adjusting the pH S2- + H+ HSHS- + H+ H2S (4) CO32-(aq) + H2O(l) HCO3-(aq) + OH-(aq) PO43-(aq) + H2O(l) HPO42-(aq) + OH-(aq) the hydroxide ion, carbonate ion, hydrogen carbonate/phosphate ion could combine with a metal to form a precipitate. The precipitate that forms can be identified in the Merck Index or similar reference book. (5) These are tests that confirm a certain product and observation. For example, adding KSCN(s) to Fe3+(aq) will form Fe(SCN)2+, a blood red solution Using all of these techniques and observing the reactions that take place enabled one to identify certain compounds easier. This is especially useful when identifying an unknown solution, and by chemically fingerprinting the cations in this lab, it will become easier to develop a plan in screening for a certain cation in the future. 3 Of course, such identification does not only occur in the academic field. As mentioned in lecture, identification of ions is important for knowing the kinds of contaminants in our water, and atmosphere. From third world countries to bottling water, the identity of what we drink is of vital importance. In Determination of Perchlorate at Trace Levels in Drinking Water by Ion-Pair Extraction with Electrospray Ionization Mass Spectrometry1, the EPA works to find out how much perchlorate is now in our drinking water. However, ion identification is not only limited to the environment. In the biochemical field, research is being done to identify a cation that is found in a growth factor of an autoantibodies and when identified can be used as a target source as stated in the article, Identification of cation-independent mannose 6-phosphate receptor/insulinlike growth factor type-2 receptor as a novel target of autoantibodies2. Methods: All procedures were as followed in Chemistry 203/205: An Introduction to Chemical Systems in the Laboratory3 except for a number things: 1.) The work was split between 3 people to cover all reactions, and the results were copied to save time 2.) The confirmation test was done individually except for one designated person who did the aluminum confirmation test because of time consumption 1 "Determination of Perchlorate at Trace Levels in Drinking Water by Ion-Pair Extraction with Electrospray Ionization Mass Spectrometry." ACS Publications - Cookie absent. Web. 29 Oct. 2009. <http://pubs.acs.org/doi/pdf/10.1021/ac9909204?cookieSet=1>. 2 "Identification of cationindependent mannose 6phosphate receptor/insulinlike growth factor type2 receptor as a novel target of autoantibodies." NCBI HomePage. Web. 29 Oct. 2009. <http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2326961/>. 3 Chemistry 203/205: An Introduction to Chemical Systems in the Laboratory. Plymouth, MI: HaydenMcNeil, LLC, 2010. Print. 4 Results4,5 Pb2+ Pb2+ (aq) + 2Cl- (aq) PbCl2 (s) PbCl2 (s) + H+ (aq) No reaction Pb2+ (aq) + SO42- (aq) PbSO4 (s) PbSO4 (s) + H+ (aq) No reaction 3Pb2+ + 2PO43- Pb3(PO4)2 (s) Pb3(PO4)2 (s) + 6H+ (aq) 3Pb2+ (aq) + 6H+ (aq) + 2PO42- (aq) Pb2+ (aq) + CO32- (aq) Pb(CO3) (s) Pb(CO3) (s) + H+ (aq) Pb2+ (aq) + CO2 (g) + H2O (l) Pb2+ (aq) + CrO42- (aq) PbCrO4 (s) 2PbCrO4 (s) + 2H+ (aq) 2Pb2+ + Cr2O72- (aq) + H2O (l) Pb2+ (aq) + 2OH- (aq) Pb(OH)2 (s) Pb(OH)2 + 2H+ (aq) Pb2+ (aq) + 2H2O (l) Beginning: Pb2+ (aq) + 2OH- (aq) Pb(OH)2 (s) Excess NaOH: Pb(OH)2 (s) + 2OH- (aq) [Pb(OH)4]2- (aq) [Pb(OH)4]2- (aq) + 6H+ (aq) Pb(OH)2 (s) + 4H2O (l) Pb(OH)2 (s) +2H+ (aq) Pb2+ (aq) + 2H2O (l) Pb2+ (aq) + 2OH- (aq) Pb(OH)2 (s) Reagents 3 M HCl Nitric Acid 3 M H2SO4 Nitric Acid 0.1 M Na3PO4 Nitric Acid 0.1 M Na2CO3 Nitric Acid 0.1 M K2CrO4 Nitric Acid 3 M NaOH Nitric Acid 19 M NaOH Nitric Acid 3 M NH4OH Nitric Acid Pb(OH)2 (s) +2H+ (aq) Pb2+ (aq) + 2H2O (l) Pb2+ (aq) + 2OH- (aq) Pb(OH)2 (s) 15 M NH4OH Nitric Acid OH-/H2S Nitric Acid H+/H2S Nitric Acid Confirmation Test Pb(OH)2 (s) +2H+ (aq) Pb2+ (aq) + 2H2O (l) Pb2+ (aq) + S2- (aq) PbS (s) Pb2+ (aq) + H2S (aq) PbS (s) + 2H+ (aq) 3PbS (s) + 2NO3 (aq) + 8H+ (aq) 3Pb2+ (aq) + 3S (s) + 2NO (g) + 4H2O (l) Pb2+(aq) + 2 I- (aq) PbI2 (s) (Yellow ppt.) PbI2 (s) + 2 I (aq) PbI4 (aq) (Colorless solution) 4 "Analytical chemistry -." Google Books. Web. 13 Nov. 2009. <http://books.google.com/books? id=ubuaqKkwsQoC&pg=PA197&lpg=PA197&dq=solubility+of+zinc+sulfide+in+acid&source=bl&ots=7udbps1NcZ&sig =Os9qmMCEm4FfNEnADaHJKCgMP4&hl=en&ei=CHz3SuPaOorQM8jw_OgF&sa=X&oi=book_result&ct=result&resnum=7&ved=0CCoQ6AEwBg#v =onepage&q=solubility%20of%20zinc%20sul&f=false>. 5 Lide, David R., ed. CRC Handbook of Chemistry and Physics. Print. 5 Reagents 3 M HCl Nitric Acid 3 M H2SO4 Nitric Acid 0.1 M Na3PO4 Nitric Acid 0.1 M Na2CO3 Nitric Acid 0.1 M K2CrO4 Nitric Acid 3 M NaOH Nitric Acid 19 M NaOH Nitric Acid 3 M NH4OH Nitric Acid 15 M NH4OH Nitric Acid OH-/H2S Nitric Acid H+/H2S Nitric Acid Confirmation Test Ba2+ Ba2+ (aq) + 2Cl- (aq) No reaction Ba2+ (aq) + SO42- (aq) BaSO4 (s) BaSO4 (s) + H+ No reaction 3Ba2+ (aq) + PO43- (aq) Ba3(PO4)2 (s) Ba3(PO4)2 (s) + H+ 3Ba2+ (aq) + 3H+ (aq) + PO43- (aq) Ba2+ (aq) + CO32- (aq) BaCO3 (s) BaCO3 (s) + H+ (aq) Ba2+ (aq) + H2O (l) + CO2 (g) Ba2+ (aq) + CrO42-(aq) BaCrO4 (s) 2BaCrO4 (s) + 2H+ (aq) 2Ba2+ (aq) + Cr2O72- (aq) + H2O (l) Ba2+ (aq) + 2OH- (aq) Ba(OH)2 (s) Ba(OH)2 (s) + 2H+ (aq) Ba2+ (aq) + 2H2O (l) Ba2+ (aq) + 2OH- (aq) Ba(OH)2 (s) Ba(OH)2 (s) + 2H+ (aq) Ba2+ (aq) + 2H2O (l) Ba2+ (aq) + NH3 (aq) No reaction Ba2+ (aq) + NH3 (aq) No reaction S2- (aq) + Ba2+ (aq) No reaction (Decomposes) H2S (aq) + Ba2+ (aq) No reaction (Decomposes) Ba2+ (aq) + CrO42- (aq) BaCrO4 (s) (Yellow ppt.) 6 Reagents 3 M HCl Nitric Acid 3 M H2SO4 Nitric Acid 0.1 M Na3PO4 Nitric Acid 0.1 M Na2CO3 Nitric Acid 0.1 M K2CrO4 Nitric Acid 3 M NaOH Nitric Acid 19 M NaOH Nitric Acid 3 M NH4OH Nitric Acid 15 M NH4OH Nitric Acid OH-/H2S Nitric Acid H+/H2S Nitric Acid Confirmation Test Bi3+ Bi3+ (aq) + Cl- (aq) No reaction Bi3+ (aq) + SO42- (aq) No reaction Bi3+ (aq) + PO43+ (aq) BiPO4 (s) BiPO4 (s) + 3H+ (aq) Bi3+ (aq) + H3PO4 (aq) Bi3+ (aq) + CO32- (aq) Bi2(CO3)3 (s) Bi2(CO3)3 (s) + 6H+ (aq) 2Bi3+ (aq) + 3CO2 (g) + 3H2O (l) 2Bi3+ (aq) + CrO42- (aq) + 2H2O (l) (BiO)2(CrO4) (s) + 4H+ (aq) (BiO)2(CrO4) (s) + 4H+ (aq) 2Bi3+ (aq) + CrO42- (aq) + 2H2O (l) Bi3+ (aq) + 3OH- (aq) Bi(OH)3 (s) Bi(OH)3 (s) + 3H+ (aq) Bi3+ (aq) + 3H2O (l) Bi3+ (aq) + 3OH- (aq) Bi(OH)3 (s) Bi(OH)3 (s) + H+ (aq) Bi3+ (aq) + 3H2O (l) Bi3+ (aq) + 3OH- (aq) Bi(OH)3 (s) Bi(OH)3 (s) + H+ (aq) Bi3+ (aq) + 3H2O (l) Bi3+ (aq) + OH- (aq) Bi(OH)3 (s) Bi(OH)3 (s) + H+ (aq) Bi3+ (aq) + 3H2O (l) 2Bi3+ (aq) + 3S2- (aq) Bi2S3 (s) 2Bi3+ (aq) + 3H2S (aq) Bi2S3 (s) + 6H+ (aq) Bi2S3 (s) + 8H+ (aq) + 2NO3- (aq) 2Bi3+ (aq) + 2NO (g) + 4H2O(l) + 3S (s) 3+ Bi (aq) + 3 I (aq) BiI3 (s) (Green-black ppt.) BiI3 (s) + I (aq) BiI4 (aq) (Orange Solution) 7 Reagents 3 M HCl Nitric Acid 3 M H2SO4 Nitric Acid 0.1 M Na3PO4 Nitric Acid 0.1 M Na2CO3 Nitric Acid 0.1 M K2CrO4 Nitric Acid 3 M NaOH Nitric Acid 19 M NaOH Nitric Acid 3 M NH4OH Nitric Acid 15 M NH4OH Nitric Acid - OH /H2S Nitric Acid H+/H2S Nitric Acid Confirmation Test Fe3+ Fe3+ (aq) + Cl- (aq) [FeCl]2+ (aq) Fe3+ (aq) + SO42- (aq) No reaction Fe3+ (aq) + PO42- (aq) FePO4 (s) FePO4 (s) + 3H+ (aq) Fe3+ (aq) + H3PO4 (aq) 2Fe3+ (aq) + 2CO32- (aq) + 3H2O (l) 2Fe(OH)3 (s) +2CO2 (g) Fe(OH)3 (s) + 3H+ (aq) Fe3+ (aq) + 3H2O (l) Fe3+ (aq) + CrO42- (aq) Fe2(CrO4)3 (s) Fe2(CrO4)3 (s) + 2H+ (aq) 2Fe3+ (aq) + 3CrO42- (aq) + H2O (l) Fe3+ (aq) + 3OH- (aq) Fe(OH)3 (s) Fe(OH)3 (s) + 3H+ (aq) Fe3+ (aq) + 3H2O (l) Fe3+ (aq) + 3OH- (aq) Fe(OH)3 (s) Fe(OH)3 (s) + 3H+ (aq) Fe3+ (aq) + 3H2O (l) Fe3+ (aq) + 3OH- (aq) Fe(OH)3 (s) Fe(OH)3 (s) + 3H+ (aq) Fe3+ (aq) + 3H2O (l) Fe3+ (aq) + 3OH- (aq) Fe(OH)3 (s) Fe(OH)3 (s) + 3H+ (aq) Fe3+ (aq) + 3H2O (l) Fe3+ (aq) + HS- (aq) Fe2+ (aq) + S (s) + H+ (aq) Fe2+ (aq) + S2- (aq) FeS (S) Fe3+ (aq) + H2S (aq) Fe2+ (aq) + S (s) + 2H+ (aq) Fe2+ (aq) + H+ (aq) No reaction Fe3+ (aq) + SCN- (aq) Fe(SCN)2+ (aq) (Blood red solution) Fe3+ (aq) + K(Fe(CN)6) (aq) KFe(Fe(CN)6) (s) (Royal blue ppt.) Reagents 3 M HCl Nitric Acid 3 M H2SO4 Mn2+ Mn (aq) + 2Cl- (aq) No Reaction 2+ Mn2+ (aq) + SO42- (aq) No Reaction 8 Nitric Acid 0.1 M Na3PO4 Nitric Acid 0.1 M Na2CO3 Nitric Acid 0.1 M K2CrO4 Nitric Acid 3 M NaOH Nitric Acid 19 M NaOH Nitric Acid 3 M NH4OH Nitric Acid 15 M NH4OH Nitric Acid OH-/H2S Nitric Acid H+/H2S Nitric Acid Confirmation Test Reagents 3 M HCl Nitric Acid 3 M H2SO4 Nitric Acid 3Mn2+ (aq) + 2PO43- (aq) Mn3(PO4)2 (s) Mn3(PO4)2 (s) + 6H+ (aq) 3Mn2+ (aq) + 2H3PO4 (aq) Mn2+ (aq) + CO32- (aq) Mn(CO3) (s) Mn(CO3) (s) + 2H+ (aq) Mn2+ (aq) + CO2 (aq) + H2O (l) Mn2+ (aq) + CrO42- (aq) MnCrO4 (s) MnCrO4 (s) + 4H+ (aq) Mn2+ (aq) + CrO42- (aq) + 2H2O (l) Mn2+ (aq) + 2OH- (aq) Mn(OH)2 (s) Mn(OH)2 (s) + 2H+ (aq) Mn2+ (aq) + 2H2O (l) Mn2+ (aq) + 2OH- (aq) Mn(OH)2 (s) Mn(OH)2 (s) + 2H+ (aq) Mn2+ (aq) + 2H2O (l) Mn2+ (aq) + 2OH- (aq) Mn(OH)2 (s) Mn(OH)2 (s) + 2H+ (aq) Mn2+ (aq) + 2H2O (l) Mn2+ (aq) + 2OH- (aq) Mn(OH)2 (s) Mn(OH)2 (s) + 2H+ (aq) Mn2+ (aq) + 2H2O (l) Mn2+ (aq) + S2- (aq) MnS (s) Mn2+ (aq) + S2- (aq) No Reaction 2Mn2+(aq) + 5BiO3-(aq) + 14H+(aq) 2MnO4-(aq) + 5BiO+(aq) + 7H2O(l) Ag+ Ag+ (aq) + Cl- (aq) AgCl (s) AgCl (s) + H+ (aq) no reaction Ag+ (aq) + SO42- (aq) No Reaction 9 0.1 M Na3PO4 Nitric Acid 0.1 M Na2CO3 Nitric Acid 0.1 M K2CrO4 Nitric Acid 3 M NaOH Nitric Acid 19 M NaOH 3 Ag+ (aq) + PO43- (aq) Ag3PO4 (s) Ag3PO4 (s) + 3H+ (aq) Ag+ (aq) + H3PO4 (aq) 2Ag+ (aq) + CO32- (aq) Ag2O (s) + CO2 (g) Ag2O (s) + 2H+ (aq) 2Ag+ (aq) + H2O (l) Ag+ (aq) + CrO42- (aq) Ag2CrO4 (s) 2Ag2CrO4 (s) + 2H+ (aq) 4Ag+ (aq) + Cr2O72- (aq) + H2O (l) 2Ag+ (aq) + 2OH- (aq) Ag2O (s) + H2O (l) Ag2O (s) + 2H+ (aq) 2Ag+ (aq) + H2O (l) 2Ag+ (aq) + 2OH- (aq) Ag2O (s) + H2O (l) Nitric Acid 3 M NH4OH Nitric Acid Ag2O (s) + 2H+ (aq) 2Ag+ (aq) + H2O (l) 2Ag+ (aq) + 2OH- (aq) Ag2O (s) + H2O (l) 15 M NH4OH Nitric Acid Ag2O (s) + 2H+ (aq) 2Ag+ (aq) + H2O (l) 2Ag+ (aq) + 2OH- (aq) Ag2O (s) + H2O (l) Excess: Ag2O (s) + 4NH3 (aq) + H2O (l) 2[Ag(NH3)2]+ (aq) + 2OH(aq) + - OH /H2S Nitric Acid H+/H2S Nitric Acid Confirmation Test Reagents 3 M HCl Nitric Acid 3 M H2SO4 Nitric Acid + [Ag(NH3)2] (aq) + 2H (aq) Ag+ (aq) + 2NH4+ (aq) 2Ag+ (aq) + S2- (aq) Ag2S (s) 2Ag+ (aq) + H2S (aq) Ag2S (s) + 2H+ (aq) 3Ag2S (s) + 8H+ (aq) + 2NO3- (aq) 6Ag+ (aq) + 2NO (aq) + 4H2O (l) + 3S(s) + Ag (aq) + I (aq) AgI (s) (Light-yellow ppt.) Cu2+ Cu2+ (aq) + 2Cl- (aq) No reaction Cu2+ (aq) + SO42- (aq) no reaction 10 0.1 M Na3PO4 Nitric Acid 0.1 M Na2CO3 Nitric Acid 0.1 M K2CrO4 Nitric Acid 3 M NaOH Nitric Acid 19 M NaOH Nitric Acid 3 M NH4OH Nitric Acid 15 M NH4OH Nitric Acid OH-/H2S Nitric Acid H+/H2S Nitric Acid Confirmation Test Cu2+ (aq) + PO43- (aq) Cu3(PO4)2 (s) Cu3(PO4)2 (s) +3H+ (aq) Cu2+ + H3PO4 (aq) Cu2+ (aq) + CO32- (aq) CuCO3 (s) CuCO3 (s) + 2H+ (aq) Cu2+ (aq) + CO2 (g) + H2O (l) Cu2+ (aq) + CrO42- (aq) CuCrO4 (s) 2CuCrO4 (s) + 2H+ (aq) Cu2+ (aq) + Cr2O72- (aq) + H2O (l) Cu2+ (aq) + OH- (aq) Cu(OH)2 (s) Cu(OH)2 (s) + H+ (aq) Cu2+ (aq) + 2H2O (l) Cu2+ (aq) + OH- (aq) Cu(OH)2 (s) Excess: Cu(OH)2 (s) + 2OH- (aq) [Cu(OH)4]2- (aq) Cu(OH)2 (s) + heat CuO (s) + H2O (l) Cu2+ (aq) + OH- (aq) Cu(OH)2 (s) Cu(OH)2 (s) + H+ (aq) Cu2+ (aq) + 2H2O (l) Cu2+ (aq) + OH- (aq) Cu(OH)2 (s) Excess: Cu2+ (aq) + 4NH3 (aq) [Cu(NH3)4]2+ (aq) [Cu(NH3)4]2+ (aq) + 4H+ (aq) Cu2+ (aq) + 4NH4+ (aq) Cu2+ (aq) + S2- (aq) CuS (s) Cu2+ (aq) + H2S (aq) CuS (s) + H+ (aq) 3CuS (s) + 8H+ (aq) + 2NO3- (aq) 3Cu2+ (aq) + 2NO (g) + 4H2O (l) + 3S(s) Cu2+ (aq) I- + (aq) CuI2 (s) (Tan ppt. and orange solution) 2 Cu 2+ (aq) + (Fe(CN)6)4- (aq) Cu2[Fe(CN)6] (s) (Red/brown ppt.) Reagents 3 M HCl Nitric Acid Ni2+ Ni2+ (aq) + Cl- (aq) No reaction 11 3 M H2SO4 Nitric Acid 0.1 M Na3PO4 Nitric Acid 0.1 M Na2CO3 Nitric Acid 0.1 M K2CrO4 Nitric Acid 3 M NaOH Nitric Acid 19 M NaOH Nitric Acid 3 M NH4OH Nitric Acid 15 M NH4OH Nitric Acid OH-/H2S Nitric Acid H+/H2S Nitric Acid Confirmation Test Reagents 3 M HCl Nitric Acid Ni2+ (aq) + SO42- (aq) no reaction Ni2+ (aq) + PO43- (aq) Ni3(PO4)2 (s) Ni3(PO4)2 (s) + 6H+ (aq) 3Ni2+ (aq) + 2H3PO4 (aq) Ni2+ (aq) + CO32- (aq) NiCO3 (s) NiCO3 (s) + 2H+ (aq) Ni2+ (aq) + CO2 (g) + H2O (l) Ni2+ (aq) + CrO42- (aq) NiCrO4 (s) 2NiCrO4 (s) + 2H+ (aq) 2Ni2+ (aq) + Cr2O72- (aq) + H2O (l) Ni2+ (aq) + OH- (aq) Ni(OH)2 (s) Ni(OH)2 (s) + 2H+ (aq) Ni2+ (aq) + 2H2O (l) Ni2+ (aq) + OH- (aq) Ni(OH)2 (s) Ni(OH)2 (s) + 2H+ (aq) Ni2+ (aq) + 2H2O (l) Ni2+ (aq) + OH- (aq) Ni(OH)2 (s) Ni(OH)2 (s) + 2H+ (aq) Ni2+ (aq) + 2H2O (l) Ni2+ (aq) + 6NH3 (aq) [Ni(NH3)6]2+ (aq) [Ni(NH3)6]2+ (aq) + 6H+ (aq) Ni2+ (aq) + 6NH4+ (aq) Ni2+ (aq) + S2- (aq) NiS (s) Ni2+ (aq) + H2S (aq) No reaction Ni2+ (aq) + 2 DMG (aq) Ni(DMG)2 (s) (Strawberry red ppt.) Zn2+ Zn (aq) + Cl (aq) No reaction 2+ 12 - 3 M H2SO4 Nitric Acid 0.1 M Na3PO4 Nitric Acid 0.1 M Na2CO3 Nitric Acid 0.1 M K2CrO4 Nitric Acid 3 M NaOH Nitric Acid 19 M NaOH Nitric Acid 3 M NH4OH Nitric Acid 15 M NH4OH Nitric Acid OH-/H2S Nitric Acid H+/H2S Nitric Acid Confirmation Test Reagents 3 M HCl Nitric Acid Zn2+ (aq) + SO42- (aq) No reaction Zn2+ (aq) + PO43- (aq) Zn3(PO4)2 (s) Zn3(PO4)2 (s) + 6H+ (aq) 3Zn2+ (aq) + 2H3PO4 (aq) Zn2+ (aq) + CO32- (aq) ZnCO3 (s) ZnCO3 (s) + 2H+ (aq) Zn2+ (aq) + H2O (l) + CO2 (l) Zn2+ (aq) + CrO42- (aq) ZnCrO4 (s) 2ZnCrO4 (s) + 2H+ (aq) Zn2+ (aq) + Cr2O72- (aq) + H2O (l) Zn2+ (aq) + 2OH- (aq) Zn(OH)2 (s) Zn(OH)2 (s) + 2H+ (aq) Zn2+ (aq) + 2H2O (l) Zn2+ (aq) + 2OH- (aq) Zn(OH)2 (s) Excess: Zn(OH)2 (s) + 2OH- (aq) [Zn(OH)4]2- (aq) [Zn(OH)4]2- (aq) + 4H+ (aq) Zn(OH)2 (s) + 4H2O (l) Zn(OH)2 (s) + 2H+ (aq) Zn2+ (aq) + 2H2O (l) Zn2+ (aq) + OH- (aq) Zn(OH)2 (s) Zn(OH)2 (s) + 2H+ (aq) Zn2+ (aq) + 2H2O (l) Zn2+ (aq) + OH- (aq) Zn(OH)2 (s) Zn(OH)2 (aq) + 4NH3 (aq) [Zn(NH3)4]2+ (aq) + 2OH- (aq) [Zn(NH3)4]2+ (aq) + 4H+ (aq) Zn2+ (aq) + 4NH4+ (aq) Zn2+ (aq) + S2- (aq) ZnS (s) Zn2+ (aq) + H2S (aq) No reaction Zn2+ (aq) + S2- (aq) ZnS (s) (White ppt.) Al3+ Al3+ (aq) + Cl- (aq) No reaction 13 3 M H2SO4 Nitric Acid 0.1 M Na3PO4 Nitric Acid 0.1 M Na2CO3 Nitric Acid 0.1 M K2CrO4 Nitric Acid 3 M NaOH Al3+ (aq) + SO42- (aq) no reaction Al3+ (aq) + PO43- (aq) AlPO4 (s) AlPO4 (s) + 3H+ (aq) Al3+ (aq) + H3PO4 (aq) 2Al3+ (aq) + 3CO32-(aq) + 3H2O (l) 2Al(OH)3 (s) + 3CO2 (g) Al(OH)3 (s) + 2H+ (aq) Al3+ (aq) + 2H2O (l) Al3+ (aq) + CrO42- (aq) Al2(CrO4)3 (s) 2Al2(CrO4)3 (s) + 6H+ (aq) 4Al3+ (aq) + 3Cr2O72- (aq) + 3H2O (l) Al3+ (aq) + OH- (aq) Al(OH)3 (s) Nitric Acid 19 M NaOH Al(OH)3 (s) + H+ (aq) Al3+ (aq) + H2O (l) Al3+ (aq) + OH- (aq) Al(OH)3 (s) Al(OH)3 (s) + OH- (aq) AlO2- (aq) + H2O (l) Al(OH)3 (s) + H+ (aq) Al3+ (aq) + H2O (l) Al3+ (aq) + OH- (aq) Al(OH)3 (s) Nitric Acid 3 M NH4OH Nitric Acid Al(OH)3 (s) + H+ (aq) Al3+ (aq) + H2O (l) Al3+ (aq) + OH- (aq) Al(OH)3 (s) Al(OH)3 (s) + 6NH3 (aq) [Al(NH)6]3+ (aq) + 3OH- (aq) [Al(NH)6]3+ (aq) + 6H+ (aq) Al3+ (aq) + 6NH4+ (aq) Al3+ (aq) + S2- (aq) No reaction (decomposes) 15 M NH4OH Nitric Acid OH-/H2S Nitric Acid H+/H2S Nitric Acid Confirmation Test Al3+ (aq) + H2S (aq) No reaction (decomposes) Al3+ (aq) + OH- (aq) Al(OH)3 (s) Al(OH)3 (s) + 3 H+ (aq) Al3+ (aq) + 3 H2O (l) Al3+ (aq) + Aluminon Al(OH)3 (s) Pb2+ 3 M HCl Ba2+ Bi3+ Fe3+ Mn2+ White ppt NR NR Lime Green ppt Redissolves NR 14 Nitric Acid no dissolve 3 M H2SO4 Nitric Acid White ppt White ppt and cloudy No dissolve Small white ppt No reaction NR NR Cloudy White ppt NR Small white ppt Redissolve White ppt Redissolve White ppt (sparse) No dissolve White ppt Redissolve Redissolve 0.1 M K2CrO4 Nitric Acid Yellow green ppt Lime green milky ppt Yellow orange ppt 3 M NaOH Nitric Acid Redissolve White ppt and then Redissolve Redissolve Less White ppt Redissolve white ppt chunky Redissolve redissolves Small white ppt Chunky white 0.1 M Na3PO4 Nitric Acid 0.1 M Na2CO3 Nitric Acid 19 M NaOH Nitric Acid 3 M NH4OH Nitric Acid 15 M NH4OH Nitric Acid OH-/H2S Nitric Acid no dissolve Small white ppt Redissolve redissolve White ppt then dissolves Gasses bubble White ppt redissolves and bubbles Silver solution/blac k ppt Small white ppt Redissolve Turns orange/ green solution no ppt Turns yellow/green solution ppt orange red ppt Orange green brown ppt (cloudy) Redissolve Redissolve gasses bubble NR Orange red ppt Redissolve Orange green brown ppt (cloudy) Redissolve White ppt Whiite ppt Brown orange ppt Dissolves and gasses. Yellow solution remains Brown thick ppt bubbles/diss olves Silver solution/blac k ppt dissolves/yellow solution Silver solution/black ppt no redissolves no Redissolve black ppt white ppt no redissovles redissolves white ppt NR no redissolves redissolves NR Yellow solution NR Brown cloudy bubbles/dissolve orange solution white ppt no ppt no redissolves H+/H2S Nitric Acid black ppt NR no redissovles 15 NR A g+ 3 M H2SO4 Nitric Acid 0.1 M Na3PO4 Nitric Acid 0.1 M Na2CO3 Nitric Acid 0.1 M K2CrO4 Nitric Acid Ni2+ Zn2+ Al3+ white ppt NR NR NR NR no dissolve NR NR NR NR NR Cloudy ppt white Cloudy white ppt Cloudy white ppt Cloudy white ppt white ppt redissolves Blue solution white ppt redissolves Cloudy white solution white ppt redissolves Cloudy white solution white ppt redissolves 3 M HCl Nitric Acid Cu2+ redissolves redissolves Dyed yellow redissolves Dyed yellow Dyed yellow NR NR NR Blue ppt Blue green ppt NR NR redissolves no dissolve blue ppt blu green ppt NR NR redissolves sky blue and foggy ppt no dissolve Cloudy, light blue NR slightly cloudy redissolved no dissolve blue ppt NR NR cloudy ppt Silver solution and black ppt clear blue silver solution and black ppt White ppt bubbles/redissolves Yellow solution white ppt Yellow ppt redissolves Blood red solution and ppt redissolves Yellow ppt forms Cloudy white solution white ppt redissolves redissolves 3 M NaOH Nitric Acid 19 M NaOH Nitric Acid 3 M NH4OH Nitric Acid 15 M NH4OH Nitric Acid - OH /H2S Nitric Acid red still, redissolves brown ppt forms redissolves brown ppt redissolves white ppt no dissolve (cloudy white ppt) NR Silver solution and black ppt redissolves no dissolve H+/H2S Nitric Acid no dissolve no dissolve no dissolve Black ppt black ppt NR Silver ppt no dissolve no dissolve Experimental: 16 no dissolve Silver solution and white ppt no dissolve Aqueous Ammonia: In this test, ammonia solution (NH4OH(aq)) dissociates in small amounts to form NH4+ and OH-. When a metal ion is introduced to the solution, it may combine with the hydroxide ions to form a hydroxide precipitate, complex with the ammonia, or not produce any visible indication of reaction. For example: (1) Cu2+ (aq) + OH- (aq) Cu(OH)2 (s) (Blue ppt) (2) Cu(OH)2 (s) + 2OH- (aq) [Cu(OH)4]2- (aq) (Royal blue solution in excess ammonia solution) Sulfide Ion: Some metal ions form precipitates with the sulfide ion. For example: (3) M2+(aq) + S2-(aq) MS(s) if [M2+][S2-] > Ksp The ion has acidic/basic properties that enable the user to control the sulfide ion concentration by shifting the equilibrium by adding adjusting the pH (4) S2- + H+ HS- (5) HS- + H+ H2S In the lab, we see this occur when silver ion is placed in basic sulfide (which produces much [S2-] based on Le Chatelier's principle when we lower the proton concentration): (6) 2Ag+ (aq) + S2- (aq) Ag2S (s) 17 Carbonate/Phosphate: This test involves the carbonate ion and the phosphate ion which act as week bases in solution and can generate a hydroxide ion: (7) CO32-(aq) + H2O(l) HCO3-(aq) + OH-(aq) (8) PO43-(aq) + H2O(l) HPO42-(aq) + OH-(aq) An incoming metal ion in such a solution may form a carbonate/phosphate precipitate, hydroxide precipitate, hydrogen carbonate precipitate, or a complex mixture of all three. For example, silver ion mixed in such a solution: 2Ag+ (aq) + CO32- (aq) Ag2O (s) + CO2 (g) (9) Discussion: The goal of this lab was to perform a series of tests between 10 cations and 11 reagents and to be able to recognize these tests for future applications, such as identifying unknown cations. In this series of tests between cations of Pb2+, Bi3+, Fe3+, Mn2+, Ag+, Cu2+, Ni2+, Zn2+, Al3+ and reagents of 3 M HCl, 3 M H2SO4, 0.1 M Na3PO4, 0.1 M Na2CO3, 0.1 M K2CrO4, 3 M NaOH, 19 M NaOH, 3 M NH4OH, 15 M NH4OH, and basic and acidic H2S. After each test that resulted in precipitation, the mixture was subjected to nitric acid to test whether or not the precipitate would dissolve back into the solution. For the most part, most of these went back into solution. The last test was the confirmatory test used to confirm the presence of a specific cation. Many trends were observed throughout the tests performed. One such trend was how the first five ions, (lead, barium, bismuth, iron and manganese) generally formed 18 precipitates with most reagents, whereas the other five (silver, copper, nickel zinc and aluminum) tended to form less. This is mostly due to the fact that copper, zinc, and aluminum hydroxides exhibited amphoteric behavior, (the ability to be both acidic as well as basic in solution). Also, the acids (hydrochloric as well as sulfuric) seemed to be the least reactive of the reagents. Of the precipitates that formed, only lead, barium and silver formed solids with the anions of the acids and tended to be of white color. Another trend involved the carbonates/phosphates and chromates, which formed precipitates and would usually dissolve again when exposed to nitric acid. The products of the chromate tended to turn the solution into a yellowish color. The bases (NaOH and NH3) tended to form precipitate with a few exceptions from zinc and aluminum ions. These exceptions could have been the result of the amphoteric behavior exhibited in lead, copper, zinc, and aluminum hydroxides. Furthermore, the ammonia solution was able to complex with other cations, such as [Cu(OH)4]2-(aq) in excess ammonia. Regarding the sulfides, the basic sulfide seemed to produce precipitate with every cation it reacted with, except for the barium ion. For the acidic sulfide, all cations except for the barium, manganese, and nickel ions produced a precipitate. However, the data and trends obtained were not absolutely accurate. In fact, it seems that many, (especially the basic reagents including NaOH and ammonia), were incorrectly observed compared to books and online resources. One reason this could have happened were because solution mixtures did not have a constant volume, and some reagent/cation may have been added more than others. This inconsistency could lead to 19 excess reagent, which could in turn lead to complex ions being formed (such as those in excess ammonia). For example: (2) Zn2+ (aq) + 2OH- (aq) Zn(OH)2 (s) Excess: Zn(OH)2 (s) + 2OH- (aq) [Zn(OH)4]2- (aq) occurs in excess 19M NaOH. If excess 3M NaOH was used, the same reaction would occur, and no precipitate would be seen, as was supposed to. Overall, this lab was successful. Out of all 120 reactions that were performed, a good majority matched up with that found in books and online resources. Although many seemed to deviate from what actually should happen quantitatively, the experiments used combined with the knowledge found outside of class in books will prove vital in determining unknown cations of future labs. 20 References: (1) "Bronsted-Lowry acids and bases." New York University. Web. 29 Oct. 2009. <http://www.nyu.edu/classes/tuckerman/honors.chem/lectures/lecture_21/node3.html>. (2) "Determination of Perchlorate at Trace Levels in Drinking Water by Ion-Pair Extraction with Electrospray Ionization Mass Spectrometry." ACS Publications - Cookie absent. Web. 29 Oct. 2009. <http://pubs.acs.org/doi/pdf/10.1021/ac9909204? cookieSet=1>. (3) "Identification of cationindependent mannose 6phosphate receptor/insulinlike growth factor type2 receptor as a novel target of autoantibodies." NCBI HomePage. Web. 29 Oct. 2009. <http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2326961/>. (4) Chemistry 203/205: An Introduction to Chemical Systems in the Laboratory. Plymouth, MI: Hayden-McNeil, LLC, 2010. Print. (5) "Analytical chemistry -." Google Books. Web. 13 Nov. 2009. <http://books.google.com/books? id=ubuaqKkwsQoC&pg=PA197&lpg=PA197&dq=solubility+of+zinc+sulfide+in+ac id&source=bl&ots=7udbps1NcZ&sig=Os9qmMCEm4FfNEnADaHJKCgMP4&hl=en&ei=CHz3SuPaOorQM8jw_OgF&sa=X&oi=book_result&ct=result& resnum=7&ved=0CCoQ6AEwBg#v=onepage&q=solubility%20of%20zinc %20sul&f=false>. 21 (6) Lide, David R., ed. CRC Handbook of Chemistry and Physics. Print. 22
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