Essay about Qualitative Analysis Discussion

856 WordsApr 23, 20084 Pages
DISCUSSION: Qualitative analysis is used to determine the presence of cations or anions present within a sample and their impurities. Information known, such as chemical and physical properties, about cations and anions can be used to determine what steps should be used to separate the sample into one, specific ion. Qualitative analysis involves forming and decomposing complex ions. Qualitative tests are very sensitive, allowing to detect a very small amount present in sample. Due to sensitivity, cleaning utensils and accurate observations are essential to results. Many basic principles are applied to determine the impurities or cations. To determine which impurities are present, scheme or flow chart is followed. Scheme is used…show more content…
In every step, there was a precipitate and supernatant liquid. This lead to students being able to determine which exact ion is present in solution. A solution containing three unknown ions (#3) was then tested. Procedure was carried out accordingly to lab manual. Determined ions present in solution were Fe3+, Cr3+, and Cu2+. The confirmatory test for Fe3+ that was used was , K4Fe(CN)6 add to a precipitate containing Fe3+. A dark blue precipitate formed which is a positive result, Fe3+ is present in this solution. Continuing procedure, Cr3+ presence was confirmed in step 9 by dissolving the precipitate with HNO3 then adding 5 drops of diphenycarbazide (dcp) solution. The supernatant was yellow then a sudden change to pretty, dark pink/purple after the first drop confirmed chromium presence. The reason for the color change is because chromium is reduced and dcp is oxidized. Further, along in the procedure, another positive test revealed the last ion present, Cu2+. The confirmatory test of copper revealed a positive result. This test was actually performed a couple of times to get a positive test due to skipping of a solution. Copper was confirmed by adding K4Fe(CN)6 to supernatant. A maroon precipitate formed, Cu2Fe(CN)6. Lastly, a solution containing four unknown ions (#6) was to be determined. The determined ions for solution #6 was iron (Fe3+), chromium (Cr3+), bismuth (Bi2+), and aluminum (Al3+). In step 5,
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