Experiment: To Determine the Ions Present in the Unknown Salt Essay

Submitted By femli
Words: 671
Pages: 3

The purpose of the experiment is to determine the ions present in the unknown salt.
To determine the ions present in the unknown salt, I performed a series of tests on the known and unknown solution. The procedure for this experiment is in the Semimicro Qualitative Analysis 1, Chemistry 112 Laboratory Manual, Spring 2014, p. 12-13. The procedure was exactly same for the known solution but for my unknown solution, there were some changes made. When repeating the hot water treatment and combining both supernatants, there was no precipitate form in my unknown solution test tube. Therefore, I found the result and continued to follow the steps for the known solution.
In my first procedure that is I-1, a white cloudy precipitate was formed when HCL was added to both of my known and unknown solutions. Since it was given that the both solutions contained Group 1 ions, supernatant was discarded and proceeded to the next step that is to separate the Pb2+ . I placed both the test tubes to the preheated water bath after adding 15-20 drops of water to the precipitates, no change observed. Allow the precipitate to settle after removing the test tubes from the water bath. Decant the hot supernatants into another test tube to test the presence of Pb2+ ions in the supernatants. When K2CrO4 was added to both the test tubes, it was observed that a cloudy yellow precipitate was formed, which indicates the presence of Pb2+ in it. Then I proceeded to the I-4, I observed that there was no precipitate in the unknown test tube which clearly indicates that there was a presence of Pb2+ ions in it. On the other hand, there was precipitate present in my known test tube. I observed that the solution was not clear with some white particles at the bottom of the test tube when HNO3 was added to the precipitate. This white precipitate was AgCl which indicates the presence of Ag+ ions in the solution.

The ions in the known and unknown solutions are different according to the data I observed. Since it was given that only group 1 ions are present, I knew that only Ag+ , Hg22+, Pb2+ ions will be present in the solutions except that due to the toxicity of Hg22+, it was not used in lab. The results that were been observed clearly states that the yellow cloudy precipitate indicates the presence of Pb2+ ions in both of my test tubes. But when I proceeded to my next procedure, I observed that there was no precipitate in the