chem lab 2 - Synthesis and Analysis of a Coordination...

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Synthesis and Analysis of a Coordination Compound May 21, 2008 Vincent Likewise Partner: Shantele McGee TA: James Eilertsen Chem 223 Section 041
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ABSTRACT: The purpose of this lab is to produce the highest possible yield of product in the highest feasible state of purity and to determine its molecular formula from percent composition. In order to do this first, synthesize a green crystal; second, calculate the percent oxalate of the crystal; third is calculate the percent potassium and percent iron through means of iron exchange; and finally, through the calculations, determine the chemical formula of the crystal. The result of the first part was a semi-transparent green crystalline structure. The results of Part 2 was calculated percent oxalate of 55.97% and 56.79%, with the mass of the C 2 O 4 2- being 0.07088 g and 0.07209 g. The percent difference of the two trials was 1.46%. In part 3 it was found that the percent potassium for each trial was 24.70% and 21.49% with a percent iron of 22.25% and 20.01%. The actual masses in grams were 0.04063 g and 0.03535 g for the potassium and 0.03661 g and 0.03239 g for the iron. The percent difference between the two trials was 13.00% for potassium and 11.53% for iron. When a secondary method was used to calculate the second equivalence point, the results were 0.05179 g and 0.04668 g with percent iron being 31.48% and 28.83% with a percent difference of 41.46% and 44.12% from the original calculation method. From this, the chemical formula of the coordination compound is K 9 [Fe 6 (C 2 O 4 ) 7 ] H 2 O – potassium heptaoxalate hexaferrate (III). THEORY: Coordination compounds are compounds that have a central metal atom bonded to a group of molecules called ligands. Occasionally, the metal will be a complex anion, which means it, and its ligand have a combined negative charge. This results in a salt attaching to the complex.
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For the experiment, it is necessary to calculate the percent oxalate in the crystal. To do this, first add a specified amount of two different acids. The purpose of the acids are to separate the coordination compound. This results in having an acidic solution where the oxalate and iron are separated in the aqueous solution and from there you can titrate to determine the number of moles of MnO 4 - which then allows the number of moles of oxalate (C 2 O 4 2- ) and percent composition to be calculated. In the third part, a resin plug is used as a means of ion exchange. The resin consists of large molecules which contain ionizable groups. In this experiment, the resin was a yellowish solid, but porous, material. What occurs when a solution is poured through the resin is that the ions of the chemical are exchanged with the resin. This causes the cation to exchange with an H 3 O + ion from the resin which is created when the resin is introduced to water. Since the cation of the solution of the green crystal is
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This note was uploaded on 03/11/2009 for the course CSS 335 taught by Professor Wolf during the Spring '09 term at Oregon State.

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chem lab 2 - Synthesis and Analysis of a Coordination...

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