chem 203 10:15:10 - The Seperation and Identification of a...

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The Seperation and Identification of a Series of Cations Raj Hirpara Chem 203, Section BB8 15 October 2010 Abstract : Qualitative analysis of the reactions between multiple cations and anions through experimental procedures
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Introduction: The goal of this lab is to qualitatively describe multiple cation reactions with different anions. This lab is concerned with determining what species is present within our sample and being able to determine the outcome of the reaction and why it is occurring. The cations we used within the lab consisted of Pb 2+ , Ba 2+ , Bi 3+ , Fe 3+ , Mn 2+ , Ag + , Cu 2+ , Ni 2+ , Zn 2+ , and Al 3+ . Each cation will be mixed with multiple anions so that the unique chemical properties can be determine for each cation, which will be used for the unknown cation lab for next week. The different properties that will be observed and recorded are things such as: precipitation, color changes, and gas evolution. Some other noticeable behavior of chemicals that will be encountered during this lab will be: amphoteric behavior of acids and bases, behavior of aqueous ammonia, behavior of sulfide ions, and behavior in carbonate and phosphate solutions. Amphoteric behavior will occur within some of the metal hydroxides used within the experiment. This means that the substance will dissolve with a hydroxide and that it will dissolve within an acid. Changing the solutions ph can also play a factor when trying to isolate different precipitates. Another possible characteristic include each species unique reaction to aqueous ammonia. As a weak base, species normally react with the free hydroxide to form hydroxide precipitates or they react to form a colored amine complex. Both of the ending results of ammonia reactions can help distinguish species and can help with separating them. Sulfide ions can also help with distinguishing and separating because it reacts and forms precipitates with many metal ions. Another useful thing about using sulfide is that we can control the pH of the solution, which can help take out certain ions and leave other ones in the solution. The concentration of the sulfide directly affects the precipitate made due to K sp values. Another way to identify and characterize solution reactions is through the use of carbonate and phosphate. Many metal ions can combine with carbonate and phosphate to form precipitates. Materials/methods: This lab utilizes well plate trays to complete and observes all the known reactions at the same time. Each cation was placed into the wells and the anions were added drop by drop to each cation. This was done repeatedly for the first seven reactions until all the reactions were observed and recorded. They could be done without having the need to rinse out the wells. However, for the reactions using 15M NH 3 , H 2 S/OH - , and H 2 S/H + were done in the fume hood in order to keep all the noxious chemicals out of the air to provide a safe and clean lab environment. The other cations had been rinsed out while
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