Investigating The Copper Content Of Brass Using Iodometry Essay
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The purpose of this experiment was to determine the copper content of brass using iodometry. This was accomplished by creating a thiosulfate solution and standardizing it by titrating using a known amount of KIO3. The second part of the experiment involved preparing a brass sample and allowing copper to react with excess iodide to form I2. The resulting I2 was then titrated with the thiosulfate standard. Both the molar concentration of thiosulfate and the weight % copper was calculated using stoichiometry.
Introduction & Background
In this experiment, the analyte is the amount of copper in an unknown brass sample. The typical range of copper in brass is 59% to 95%. Iodometry is used to determine the amount of copper in brass. There are two main reactions in this process. The first reaction involve copper reacting with excess iodide to form iodine as shown in this equation: 2Cu2+ + 4I 2CuI + I2. The resulting iodine is then titrated with thiosulfate: I2 + 2S2O32- 2I- +S4O62-. The end point is reached when all I2 have reacted. With a known amount of thiosulfate used, the amount of copper in brass can be determined using stoichiometry. The titration process need to proceeds in a neutral or slightly acidic solutions. In basic alkaline solution, the thiosulfate ion is oxidized to tetrathionate in addition to sulfate. In an acidic environment, the thiosulfuric acid that formed in the process can go through an internal redox reaction to form…