Unknown Cation TestAbstractIn this experiment a scheme was developed to separate cations from a solution of unknown cations. The scheme was developed from previous labs. There was a possibility of Ag+, Pb2+, Cu2+¯, Fe3+, and Ni2+ to be present in the solution, and the scheme was carried out to find which ions were present. In this case Pb2+, Cu2+, and Fe3+, were in the solution.IntroductionThe overall purpose of this lab is to develop a scheme to separate and identify three unknown cations from a solution, and then perform this scheme to perfection. This will be done by adding different solutions to the main cation solution and carefully watching to see what precipitates. The techniques that will be used in this lab include centrifuging and decanting. A centrifuge rotates very quickly to separate substances with different densities1. Decanting is defined as pouring gently as to not disturb the sediment. This can also be done by a pipet to ensure none of the precipitate or sediment is disturbed1. Making schemes is also a major technique in this lab. The process of making ascheme is always used in science for all labs. This includes figuring out what the end result wanted is and then developing ideas on how to achieve this end result. Also the concept of amphoteric behavior can be seen in this lab. This behavior is a solution that can have the properties of an acid or a base. Finally the concept of complex ions needs tobe addressed in this lab. A complex ion is usually an ion that in excess of a solution, ligands surround and form a coordination complex. This knowledge will be used to determine the separation scheme.In this lab there will be a solution with three unknown cations. Of these three there are five possibilities, which include Ag+, Pb2+, Cu2+, Ni2+, and Fe3+. In the scheme that is mentioned later in the procedure, there are five possible reactions that will occur inthis lab. They are as follows:Ag+ (aq) + Cl- (aq)  AgCl (s)Pb2+ (aq) + Cl- (aq)  PbCl2 (s)Cu2+ (aq)+ S2- (aq) CuS (s)Fe3+ (aq)+ OH- (aq)  Fe(OH)3 (s)(1)(2)(3)(4)2The following will be a confirmation test as shown in the scheme, because Nickel will not precipitate with the solutions present. Also the NH3 will be basic.Ni2+ (aq) + DMG (s) + NH3 (aq)  Ni(DMG)2This solution created should be strawberry red color. These are the main reactions that take could take place in this lab. Not all of them will due to the fact that there will only be three of the five listed ions present.The separation and identification of unknown cations is very important in the world today. Many water supplies are contaminated with these unknown cations and without separation schemes and techniques these would be consumed by humans and animals alike. A Geochemical process in Denmark was used to separate unwanted cationsfrom the water from freshwater and saltwater. This process helps many different living things and is very important3. A method was designed in China to separate cations from waste to help cleanse the solutions to make them easier to dispose of4. Also the use of cation treatment as seen in china is seen in many other ways to treat wastewater in many other instances. Also there are cases that also treat acid mine drainage by developimg a scheme and carrying it out to rid of unwanted cations5. In all of these instances a group ofscientists developed a scheme to separate cations, and then carried out that idea to determine which cations were present and the way to rid of them from the solution. This is exactly what will be done in this lab.Materials and MethodsA detailed list of the materials and methods can be found in the lab manual6. The procedure that was followed can also be seen written out in the lab notebook, or the pre lab and is as followed. The unknown solution, solution LS-19, had a possibility of having Ag+, Pb2+, Cu2+¯, Fe3+, and Ni2+. First the solution was separated into different equal parts in the case of an error occurring while performing the lab. The solution was separated into four different test tubes. The separation scheme was not altered from the original. First three drops of 3 M HCl was added to one of the parts of the solution in the first test tube. This caused a precipitate to be formed, so the solution was mixed, centrifuged and then decanted into a different test tube. The precipitate could have been AgCl, PbCl2 or both. Then water was heated to 100ºC and the DI water was added to this precipitate to (5)3determine which cation was in the solution. Because all of it dissolved, Pb2+ was in the solution. Next KI was added to confirm lead was in this solution and the solution turned yellow, then clear again in excess KI. It was determined that AgCl was not found in the solution because after the boiling DI water was added, no precipitate was left undissolved. Next the decanted solution was taken to the fume hood to perform the acidicH2S tests. When a few drops of acidic H2S was added to the decanted solution a very minimal amount of precipitate formed, almost unable to be seen. After waiting for a few minutes to ensure the reaction was complete, parafilm was put onto the top of the test tube with the H2S to ensure no harmful or foul smelling gases were released into the air. This solution was taken out of the fume hood and then centrifuged and decanted to a new test tube, and it was shown that CuS was found in the solution. Next NH4OH was added along with NH4Cl to the decanted solution and a precipitate formed. This precipitate was found to be Fe(OH)3. The NH4Cl was added in order to buffer the solution. A confirmation test was then performed, in order to determine if Ni2+ was in the solution. This confirmation test included putting DMG in the solution made basic by NH4OH. The nickel confirmation test should have turned strawberry red, but it turned cherry red, inferring that Nickel was not in the solution. This caused some error, which will be discussed in the discussion. Thus, in the end, the cations in the solution were Cu2+, Pb2+, and Fe3+. The following is the separation scheme used to determine the unknown cations.4ResultsThe three cations in the solution were Fe3+, Pb2+, and Cu2+. This was found by the separation scheme.Table 1: Reactions that occurred in the lab# Reagents Reaction Observations1 Pb2+, HCl Pb2+(aq) + 2Cl- (aq) PbCl2(s)White precipitate formedDissolved when added to H2O2 Pb2+, KI Pb2+(aq)+2I-(aq)  PbI2(s)In excess: PbI2(aq) + 2I-(aq) 