Lab 5 - Qualitative Analysis

The soluble ion is separated by collecting the solid

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Unformatted text preview: ble ion from the others. The soluble ion is separated by collecting the solid at the bottom of a test tube in a ce ntrifuge , a device that creates a centrifugal force by rotation. After the precipitate is compacted, the s upe rnatant (the liquid solution above the solid) is de cante d (carefully poured off) into a separate container. The soluble ion is in the liquid supernatant while the insoluble ion is in the solid precipitate. Thus they are physically separated from each other when the liquid is poured off, leaving the solid behind. The solid precipitate is typically washed with water to help remove any traces of the soluble ions that www.webassig encheml1/lab_5/manual.html 1/6 4/15/13 Lab 5 - Qualitative Analysis remain. This prevents "false positive" test results later on. In order to devise a scheme for separating a mixture of the cations in this lab, each ion will be tested individually for its solubility characteristics. You must carefully observe the behavior of each ion under the test conditions described in the procedure. The presence or absence of a solid and the accompanying colors of solids and solutions will provide important clues both for your separation scheme and the eventual identification of the ions. Deviation from the procedure may give different results, so be consistent in your technique. When you think you have a particular ion isolated in solution, how do you prove it? One way is to do a chemical test on the solution and show that the results of that test are identical to those of a genuine sample of the ion. This type of confirmatory test forms the basis for identifying the ions you think you have separated. A true confirmatory test is unique to a particular ion. In other words, the presence of other ions will not give a false positive result. For the three cations in this experiment, the confirmatory test will be based on the addition of iodide ions. You will observe the behavior of the three cations in the presence of iodide, and then apply this test whenever you think you have isol...
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This document was uploaded on 01/22/2014.

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