Qualitatively Analyzing the Unknown
Introduction: Qualitative analysis is the reason chemists can take an unknown compound and run it through certain tests to confirm or reject what elements the compound contains. Standard tests have been created by the testing of a known element and observing the qualities of that element in that certain test. The purpose of this lab was to show the vitality of qualitative analysis in discovering what an unknown substance is composed of, and in this lab that substance was an unknown salt, composed of a cation and anion. Being able to take an unknown substance and finding its identity is so important because in the real world compounds and chemicals aren’t always in nicely labeled bottles.
Materials and Methods:
Part 1: First, 10 drops of each of the 5 cations were added, K+, Fe3+, Zn2+, and Co2+, respectively to 10(2 for each cation) different centrifuge tubes. Next a confirmation of all the ions to be cations was carried out by the Metal Hydroxide and Ammonium Hydroxide tests. In the Metal Hydroxide test drops of 6M NaOH were added to the 5 different cations until a precipitate was formed (or not formed after a maximum of 20 drops being added). Next the Ammonium Hydroxide test was performed on the remaining set of 5 cations, in which 15M NH4OH was added by drop until a precipitate was formed or 20 drops were added with no change. Then an additional 10 drops of the 15M NH4OH were added to each of the 5 cations. After finding that all were in fact cations each was tested by way of flame tests to confirm the actual identity of the cations. First 20 drops of each metal solution were added to 5 different centrifuge tubes and then a Bunsen burner was set up and lit. Then a Nichrome loop was dipped in HCl and placed into the flame to clean the Nichrome of any previous contaminating ions. After repeating the cleaning process, each cation was tested (cleaning the loop in between tests with the HCl) to confirm their identity by the...