Qualitative Analysis of Buffer Solutions

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Qualitative Analysis II


In this experiment procedures were devised that enabled us to separate, properly identify mixtures of six different cations. After each cation is identified the procedures that were devised were used to identify which cations were present in an unknown solution. Qualitative analysis deals with the separation and identification of six cations: Ag+, Al3+, Ba2+, Ca2+, Fe3+, and Pb2+. Solubility equilibria, amphoterism, and complex-ion equilibria play important roles in the separation and identification of the unknown solution.


Test to Establish General Classes (first week) - First test tubes were obtained, and cleaned. Next the solutions of silver nitrate, aluminum nitrate, barium nitrate calcium nitrate, iron (III) nitrate, and lead (II) nitrate were all put into test tubes, and labeled. Next, the HCl was added and mixed thoroughly, and observations were recorded. Next new cations were put into new test tubes, and the same test was ran with buffered ammonia, and then with ammonium carbonate.

Then all of the precipitates from each test were centrifuged, and decanted. The precipitates were all washed to remove all of the ammonium carbonate. The precipitates were treated with HCl, and observations were recorded.

Dividing the Cations into General Classes- Using the results obtained from the preceding tests schemes for separating the six cations into three general classes by completing the flow charts.

Examining the Hydrochloric Acid Class- First twenty drops of the 0.1M solutions containing the nitrates of the cations were placed into separate test tubes, and labeled. Then hydrochloric acid was added, and each tube was centrifuged. Precipitate was decanted and then washed. The precipitation was then placed in a boiling bath, and stirred routinely. Potassium chromate was added to the test tube that the precipitate dissolved. The water was then decanted from the precipitate that didn't dissolve, and ammonia...