University of Santo Tomas PHA612 Lab Expt 3 PDF

EXPERIMENT 3: SEPARATION OF THE BASIC CONSTITUENTS INTO GROUPS PHA612 – Pharmaceutical Inorganic Chemistry (with Qualitative Chemistry) Session starts at 1:15 PM Objectives: 1. Using the solubility principles, group the ions that form a p...

EXPERIMENT 3: SEPARATION OF THE BASIC CONSTITUENTS INTO GROUPS PHA612 – Pharmaceutical Inorganic Chemistry (with Qualitative Chemistry) Session starts at 1:15 PM Objectives: 1. Using the solubility principles, group the ions that form a precipitate with a particular reagent. 2. Develop a systematic method to facilitate the identification of ions. Fundamental Concepts Elements may be classified according to: 1. Their atomic numbers (Periodic Table) 2. The reactions and properties of their ions  Basic Constituents/ Cations Grouped according to their properties Those ions which form compounds having similar properties are placed in a single group Makes use of group precipitants Keynotes by: Adrien Kyle M. Jacinto, RPh, MS  Group I Cations: Silver Group Cations Group Group Members Result Precipitant I. Insoluble 3M HCl Pb+2, PbCl2, Chlorides Hg22+ or Hg+1, Hg2Cl2, Ag+1 AgCl – White ppt Keynotes by: Adrien Kyle M. Jacinto, RPh, MS Table Source: CPSC, 2023 ©  Group II Cations: Hydrogen Sulfide Group Cations Group Group Members Result Precipitant II. Acid-Insoluble Adjust H+ to Cu Subgroup: Na2S insoluble CuS – Black ppt Sulfides 0.3M and Cu+2, Bi+3, Cd+2, Pb+2 Bi2S3 – Brown-Black ppt saturate with CdS – Yellow ppt H2S PbS – Black ppt (Source: Thioacetamide) Sn Subgroup: Na2S soluble Sn+2/+4, As+3/+5, Sb+3/+5, SnS – Brown ppt Hg+2 SnS2 – Yellow ppt As2S3 and As2S5 – Yellow ppt Sb2S3 – Orange red ppt HgS – Black ppt; if Red (Cinnabar) Keynotes by: Adrien Kyle M. Jacinto, RPh, MS Table Source: CPSC, 2023 ©  Group II Cations: Hydrogen Sulfide Group To precipitate members of group II, acid concentration of the solution must be adjusted to 0.3M Lower than 0.3M will cause the sulfides of group III to precipitate with group II Higher than 0.3M will dissolve the sulfides of some members of group II cations especially Bismuth, Cadmium, Lead, Tin, Antimony but not Copper, Mercury and Arsenic ions Keynotes by: Adrien Kyle M. Jacinto, RPh, MS Group II Cations: Hydrogen Sulfide Group Components of sodium sulfide reagent: Na2S – precipitates the sulfide of the ions Na2S2 – oxidized the ions into their higher oxidation states NaOH – prevents the hydrolysis of sulfides Precipitation with Hydrogen sulfide gas Sources of Hydrogen sulfide gas (H2S) Reaction of HCl with FeS (Pyrite) in the Kipps Type Generator FeS + 2HCl → FeCl2 + H2S↑ Hydrolysis of thioacetamide in a slightly acidic or basic media at elevated temperature CH3CSNH2 + H2O → CH3CONH2 + H2S↑ 10  Group III Cations: Ammonium Sulfide Group Cations Group Group Precipitant Members Result III. Base-Insoluble (NH4)2S or Fe Subgroup: FeS and Fe2S3 – Black ppt Sulfides and Combination of NaOH and Na2O2 CoS – Black ppt Hydroxides NH4Cl, NH3, and H2S insoluble NiS – Black ppt Fe+2/+3, Co+2/+3, Ni+2, MnS – Flesh or Salmon Mn+2 ppt Al Subgroup: Al(OH)3 – White NaOH and Na2O2 soluble gelatinous ppt Al+3, Cr+3, Zn+2 Cr(OH)3 – Grayish green ppt ZnS – White ppt Keynotes by: Adrien Kyle M. Jacinto, RPh, MS Table Source: CPSC, 2023 ©  Group IV Cations: Alkaline Earth Group Cations Group Group Members Result Precipitant IV. Insoluble (NH4)2CO3, NH3, Alkaline Earth MgCO3, CaCO3, Carbonates NH4Cl, 95% Metals: SrCO3, BaCO3 – EtOH mixture Mg+2, Ca+2, Sr+2, Ba+2 White ppt Keynotes by: Adrien Kyle M. Jacinto, RPh, MS Table Source: CPSC, 2023 ©  Group IV Cations: Alkaline Earth Group 95% Ethanol is needed for complete precipitation MgCO3 Becomes very soluble in the presence of a high concentration of ammonium salt It may not be precipitated with alkaline group and remain in solution together with the alkali or soluble group Keynotes by: Adrien Kyle M. Jacinto, RPh, MS  Group V Cations: Alkali/Soluble Group Cations Group Group Members Result Precipitant V. Soluble group None Alkali Metals: (-) Li+, Na+, K+ Hypothetical Alkali metal: NH4+ Keynotes by: Adrien Kyle M. Jacinto, RPh, MS Table Source: CPSC, 2023 © EXERCISES SOLUTION CONTAINING: Identify the group of the cations Mn +2 Ca +2 Na +2 Hg2+2 Cd +2 Sn +4 Zn +2  A solution in a test tube containing the following ions: Cu+2, Co2+ , As3+ , K+ , Ag+, Zn2+ , Sr2+ Add 3M HCl Ppt: Centrifugate: Adjust Acid Conc. to 0.3 M + H2S Centrifugate: Ppt: Add (NH4)2S Add Na2S Ppt: Centrifugate: Ppt: Centrifugate: As3+ Add NaOH & Na2O2 Add NH3, NH4Cl, (NH4)2CO3 & : 95% :C2H5OH Ppt: Centrifugate: Centrifugate: Ppt:  A solution in a test tube containing the following ions: Cu+2, Co2+ , As3+ , K+ , Ag+, Zn2+ , Sr2+ Add 3M HCl Ppt: AgCl white ppt. Centrifugate: Cu+2, Co2+ , As3+ , K+ , Zn2+ , Sr2+ Adjust Acid Conc. to 0.3 M + H2S Centrifugate: Co2+ , K+ , Zn2+ , Sr2+ Ppt: CuS & As2S3 Add (NH4)2S Add Na2S Ppt: ZnS & CoS Centrifugate: As3+ Add NaOH & Na2O2 Centrifugate: Sr2+ K+ Add NH3, Ppt: CuS NH4Cl, (NH4)2CO3 & 95% C2H5OH : Ppt: Co(OH)3 Centrifugate: Zn2+ Centrifugate: K+ Ppt: SrCO3 Experiment 3: Separation of the Basic Constituents into Groups Procedure Separation of Basic Constituents 3-1. Place 10gtts each of Ag+, Sb+3, Zn+2, Ba+2 and Na+ + 1-2gtts 3MHCl Stir and centrifuge Ppt: Grp 1 3-2. CENTRIFUGATE :Evaporate to almost dryness + 1gtt 12MHCl and 39 gtts of distilled water Saturate with H2S by adding 10 gtts of 10% thioacetamide Heat in water bath for 10 mins Ppt: Grp 2 3-3.CENTRIFUGATE: Alkalinize with NH4OH and 4 gtts NH4Cl Saturate with H2S by adding 10 gtts of 10% thioacetamide Heat in water bath for 10 mins Stir and centrifuge Ppt: Grp 3 Separation of Basic Constituents 3-4.CENTRIFUGATE: Evaporate to half of its volume + 3gtts 6M NH4OH and heat in water bath + 15gtts 3M (NH4)2CO3 + 15gtts 95% C2H5OH.Stir and centrifuge Ppt: Grp 4 Centrifugate: Grp 5 Thank you!