EXPERIMENT QA2 Alkaline Earth Metal Ion Qualitative Analysis The chemistry of the Alkaline Earth Metals (Group II) Ions are very similar, however they do have slightly different solubilities with the appropriate Anion Reagent. In this experiment you will examine the anions capable of separating the Metal ions and you will devise a separation scheme that will allow you to successfully identify the contents of an unknown containing a mixture of the metal ions. SOLUTIONS Ba(NO3)2 Sr(NO3)2 Ca(NO3)2 Mg(NO3)2 REAGENTS K2CrO4 (NH4)2 C2O4 (NH4)2 SO4 NH3 ---> ---> ---> ---> Cation Used Ba2+ Sr2+ Ca2+ Mg2+ ---> ---> ---> ---> Anions Used CrO42Chromate C2O42Oxalate 2SO4 Sulfate OH1Hydroxide Barium Strontium Calcium Magnesium PROCEDURE: Reagent\Soln Ba2+ Sr2+ Ca2+ Mg2+ 2CrO4 C2O42SO42OH11. In a 96 well reaction plate place a couple drops of each SOLUTION. Add a couple drops of each REAGENT to each SOLUTION and make observations. Your data table should look as above: 2. Using the data from above, devise a SEPARATION SCHEME that will allow you to separate a mixture of the alkaline earth metal ions from each other. Mr. Godfrey will explain how in class. A skeletal framework for your separation is provided on the back. Have your scheme OK’d by the teacher before you go any further!! 3. Obtain an unknown from the teacher. Record its code letter in your data book. Add about 1 cm of the unknown to a small test tube and add your first reagent. You MUST follow the separation scheme you developed!! a. Add reagents drop wise; If no precipitate is observed follow your scheme to the next reagent. b. If, after you add a few drops of a reagent you get a precipitate you must remove all of that precipitate before you can go on. To do this, add several drops of reagent until you no longer see precipitate forming. Centrifuge. To the centrifuged test tube and solution, add another drop of reagent. If no more precipitate forms, drive on. If more precipitate forms, add enough reagent to get it all then re-centrifuge. Ba+2, Sr2+, Ca2+, Mg2+ Reagent: Soln PPT 3 Cations PPT Reagent: 2 Cations PPT Reagent: 1 Cation PPT Reagent: PROCESSING THE DATA: In your abstract, explain the ions you have and don’t have. Your lab grade will be based upon a. A well written abstract b. The correct identification of all unknown ions. c. Well documented data. d. A completed separation scheme showing the correct formulae of all reagents and precipitates. ADDITIONAL, OPTIONAL PROCEDURE: FLAME Test 1. Add 1 mL of the appropriate cation solution (except magnesium) solution to 1 ml of the carbonate reagent in a small test tube. CENTRIFUGE, decant and discard the liquid. Add 6 M HCl to the carbonate precipitate to dissolve it. Just a drop or two will do. 2. Get a flame test loop. Dip the loop into the solution from above then into a Bunsen burner flame and note the color. 3. Repeat steps 1 & 2 using a fresh sample of the unknown.