Qualitative Analysis: Solubility Data Table

Qualitative Analysis Lab
Solubility Data Table Cations | Ag+ | Pb2+ | Cu2+ | Ni2+ | Ba2+ | NaCl | White ppt, AgCl(soluble in 12M HCl, soluble in sln of good complexing agent, 6M NH3) | White ppt, PbCl2(soluble in hot water, soluble in 12M HCl, soluble in sln of xs NaOH) | Soluble – no ppt | Soluble – no ppt | Soluble – no ppt | Na2CO3 | White ppt, Ag2CO3(soluble in 6M HCl, soluble in sln of good complexing agent) | White ppt, PbCO3(soluble in 6M HCl, soluble in sln of good complexing agent) | Blue ppt, CuCO3(soluble in 6M HCl, soluble in sln of good complexing agent) | Green ppt, NiCO3(soluble in 6M HCl, soluble in sln of good complexing agent) | White ppt, BaCO3(soluble in 6M acetic acid, soluble in 12M HCl) | NH3 | Brown ppt, Ag2O(soluble
in xs NaOH) | Pale Blue ppt, Cu(OH)2(soluble in 6M HCl, soluble in sln of good complexing agent) | Green Gel becomes crystalline upon standing, Ni(OH)2 | ? | S2- (acidic pH = 0) | Black ppt, Ag2S(soluble in hot 6M HNO3) | Black ppt, PbS(soluble in hot 6M HNO3) | Black ppt, CuS(soluble in hot 6M HNO3) | No ppt | | S2- (basic pH = 9) | Black ppt, Ag2S(soluble in hot 6M HNO3) | Black ppt, PbS(soluble in hot 6M HNO3) | Black ppt, CuS(soluble in hot 6M HNO3) | Black ppt, NiS(soluble in hot 12M HCl) | |
Perform the Separation/Identification Experiment as follows;
• Read through the Discussion and Cations sections on pages 450 to 452, skipping the last paragraph on page 452. This is where you will get your Purpose Statement and Background information for your Prelab. Do the Prelab questions 1, 2, 3, 4 on pages 435 and 436. Also do the Prelab questions 1, 2, 3, 6, 7 on pages 455 and 456.
• Mix a Known from 1 mL each of the standard solutions of all 5 cations. You will run the separation/analysis of your Unknown and Known side by side. Record all observations for both after each
The NiS should become insoluble and the formation of this black precipitate confirms the presence of Ni2+. Ca2+ will remain in solution. Centrifuge the test tube and decant the supernatant liquid (supernatant III) into a clean test tube for further analysis of Ca2+ (Group IV). Wash the precipitate with 1 mL of distilled water, centrifuge and discard the wash solution. Carefully add 20 drops of 12M HCl and heat the test tube in a hot water bath in the hood. If precipitate is still present, add 3 more drops of 12M HCl and continue heating. Remove the test tube from the heat and CAREFULLY add 6M NH3 solution until neutral. Add 3 drops of dimethylglyoxime solution and watch for the formation of a cherry red precipitate – this confirms the presence of Ni2+.

Analysis of Group IV – Ca2+ Take the supernatant III and pour half of the solution into a second clean test tube. To one test tube add drops of 1M Na2CO3 solution and watch for formation of a white CaCO3 precipitate. (Ca2+ would also be confirmed by; to the second test tube add drops of 1M K2CrO4 solution and watch for formation of a canary yellow CaCrO4 precipitate.) The other test tube of solution can be used for a flame test – reddish flash confirms Ca2+.

Use the Outline below when collecting your data and writing your lab