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chm085_qualitative_analysis - QUALITATIVE ANALYSIS...

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QUALITATIVE ANALYSIS Qualitative analysis is used to separate and detect cations and anions in a sample substance. Separation is dependent on the differences in solubilities of the compounds formed and the colours of the compounds and ions present. The following tests should allow you to devise or modify a procedure for the identification of a limited number of ions. Part A: Preliminary Observation Of Cations (Procedure) 1. Place five drops of silver nitrate into a centrifuge tube. Add HCl(aq), drop by drop, until any precipitation ceases 2. Place five drops of iron III nitrate into a centrifuge tube. Add NH 4 OH(aq), drop by drop, until any precipitation ceases. Centrifuge the mixture and save the precipitate. To the precipitate add five drops of NaOH(aq). Centrifuge the mixture and save the precipitate. To the precipitate, add HCl(aq), drop by drop, until the precipitate dissolves. Add several drops of potassium ferrocyanide solution. Note the results. 3. Place five drops of aluminum nitrate into a centrifuge tube. Add NH 4 OH(aq), drop by drop, until any precipitation ceases. To see the precipitate, it may be helpful to hold the tube up to a window. Centrifuge the mixture and save as much of the precipitate as possible. To the precipitate add NaOH(aq) drop by drop until the precipitate dissolves. Add HCl(aq), drop by drop. Note the results. 4. Place five drops of copper II nitrate into a centrifuge tube. Add NH 4 OH(aq), drop by drop. Note the results. 5. Place five drops of calcium nitrate into a centrifuge tube. Add five drops of HCl(aq). Now add ten drops of NH 4 OH(aq). Finally add NaOH(aq) drop by drop. It may take time for the precipitate to appear at this point. Note the results.
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FLAME TESTS The flame test is used to visually determine the identity of an unknown metal of an ionic salt based on the characteristic colour the salt turns the flame of a bunsen burner. A thin wire attached to a metallic or wooden handle is used for these tests. The wire may be cleaned by dipping in hydrochloric or nitric acid, followed by rinsing with distilled water. Test the cleanliness of the loop by inserting it into a bunsen burner flame. If a burst of color is produced, the loop was not sufficiently clean. Ideally, a separate loop is used for each sample to be tested, but a loop
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