Pathways and Methodology Chemistry Crisis Pathways and Methodology Created by Jared Mader

Chemical Identification The tests found in the identification methods listed below will help you identify the unknown chemicals used by the food manufacturer: Cation Identification Anion Identification Resources Choose One Created by Jared Mader

Cation Identification When testing cation, the following methods may be employed: Chemical Color Identification Solubility Flame Test for Identification Addition of sodium hydroxide solution Addition of ammonia solution Addition of potassium iodide solution Ammonium Identification Addition of Hydrochloric Acid Main Created by Jared Mader

Anion Identification When testing anion, the following methods may be employed: Addition of silver nitrate to a slightly acidic solution of compound Addition of sulfuric acid* Polyatomic anion tests Addition of Lead(II) Nitrate Main Created by Jared Mader

Chemical Color Identification Compounds of some transition metals have unique color: Copper: blue, blue/green Chromium: green, purplish/green Iron: pale green, yellow, amethyst Nickel: green Cobalt: red • Students must realize that this is only a starting point to guide more testing. Back Created by Jared Mader

Solubility The following are insoluble: Halides of lead and silver Sulfates of barium, calcium, strontium, and lead Carbonates of all metals with the exception of alkali metals • Students must realize that this is only a starting point to guide more testing. Back Created by Jared Mader

Flame Tests Upon using cue tip dip flame test, color emission will be: Sodium: bright yellow/orange Potassium: lilac Strontium/Lithium: bright red Barium: pale green Calcium: brick/orange red Copper: green with blue/white center Lead: Whitish in color • Prior laboratory involving the teaching of the Flame Test Method must be completed. Back Created by Jared Mader

Sodium Hydroxide Addition Carefully add dilute NaOH solution to solution of unknown White precipitate: calcium, zinc, strontium, aluminum, and lead Blue precipitate, but turns black upon heating: copper Green precipitate: Nickel Gray/green, turning brown on standing: Iron(II) Red precipitate: Iron(III) Blue precipitate, turning gray upon standing: Cobalt • 1M stock solution of NaOH should be prepared by teacher and placed in dropper bottles. • Litmus paper must be available Back Created by Jared Mader

Ammonia Solution Addition Carefully add dilute NH3 solution to solution of unknown White precipitate: calcium, aluminum, lead, and zinc Blue precipitate, turning to deep blue solution as more NH3 is added : copper Coral Blue Solution: nickel Gray/green, turning brown on standing: Iron(II) Red precipitate: Iron(III) Blue precipitate, turning gray upon standing: Cobalt • Stock solution of ammonia must be prepared and stored in labeled dropper bottles. Back Created by Jared Mader

Addition of Potassium Iodide Solution Carefully add dilute KI solution to solution of unknown Yellow precipitate: lead • Potassium iodide solution must be prepared and stored in labeled dropper bottles. Back Created by Jared Mader

Addition of Potassium Chromate Solution Carefully add dilute potassium chromate solution to solution of unknown Fine crystalline precipitate: zinc, cobalt, iron(III), nickel, or lead • Potassium iodide solution must be prepared and stored in labeled dropper bottles. Back Created by Jared Mader

Addition of HCl Solution Carefully add dilute HCl solution to solution of unknown White Precipitate: lead • Potassium iodide solution must be prepared and stored in labeled dropper bottles. Back Created by Jared Mader

Addition of Silver Nitrate Carefully add a dilute AgNO3 solution to a slightly acidic solution of unknown Create slightly acidic solution by adding several drops of HNO3 White precipitate: chloride Cream precipitate: bromide Yellow precipitate: iodide Back Created by Jared Mader

Addition of Sulfuric Acid *MUST BE CONDUCTED IN FUME HOOD Carefully add several drops of concentrated sulfuric acid to solution of unknown Brown acidic fumes: bromide or nitrite Purple acidic fume: iodide Back Created by Jared Mader

Addition of Lead(II) Nitrate Carefully add several drops of lead(II) nitrate solution to a solution of unknown Yellow precipitate: iodide White precipitate: bromide, chloride or sulfate Back Created by Jared Mader

Polyatomic Ion Tests To a solution of the unknown, carefully add several drops of: COLD NaOH = strong ammonia smell and litmus turns red to blue = ammonium ion Dilute solution of potassium permanganate and HCl = turns from purple to clear = nitrite ion Ammonium solution = strong ammonia smell, no precipitate and litmus turns red to blue = hydroxide ion If soluble, add AlNO3 solution = white precipitate = hydroxide ion Heat solid in a test tube with a burner = brown gas(nitrogen dioxide) = nitrate ion [MUST COMPLETE IN FUME HOOD] HCl and BaCl2 = white precipitate = sulfate ion Dilute HCl = vigorous bubbling of CO2 gas = carbonate ion Gently heat solid = color change/release of CO2 = carbonate ion Back Created by Jared Mader

Polyatomic Ion Tests To a solution of the unknown, carefully add several drops of: COLD NaOH = strong ammonia smell and litmus turns red to blue = ammonium ion Dilute solution of potassium permanganate and HCl = turns from purple to clear = nitrite ion Ammonium solution = strong ammonia smell, no precipitate and litmus turns red to blue = hydroxide ion If soluble, add AlNO3 solution = white precipitate = hydroxide ion Heat solid in a test tube with a burner = brown gas(nitrogen dioxide) = nitrate ion [MUST COMPLETE IN FUME HOOD] HCl and BaCl2 = white precipitate = sulfate ion Dilute HCl = vigorous bubbling of CO2 gas = carbonate ion Gently heat solid = color change/release of CO2 = carbonate ion Back Created by Jared Mader

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