Synthesis and Component Analysis of an Iron (Iii) Oxalate Complex

Topics: Ligand, Titration, Stoichiometry Pages: 38 (7868 words) Published: January 22, 2013
Experiments 4A-C:
Synthesis and Component Analysis of an Iron (III) Oxalate Complex My Name
TA, Section B##
Work Performed on 10/23, 10/30, & 11/4, 200#
Report due Tuesday, November ##, 200#
1. Abstract
This experiment initially involved the synthesis of an iron (III) oxalate complex with the general formula Kw[Fex(C2O4)y]·zH2O. The variables x, y, and z were determined through the duration of the entire experiment. From 1.2000g of Fe(NH4)2(SO4)2 were synthesized 1.1###g of K3[FeIII(C2O4)3]·3H2O, owing for a percentage yield of 74.###%. A percentage yield of 11#.##% was also calculated, had the final product been K[FeIII(C2O4)2]·2H2O. This value was rejected because experimental errors are never to exceed theoretical values, which are taken on assumption that the experiment is carried out in entirely ideal environmental settings, which are impossible to attain entirely. In 4B, redox titrations were used to calculate the relative composition of oxalate within the iron (III) oxalate salt. The millimoles of oxalate were found to be.64#, .63#, .62#, and .62#, for trials A-D, respectively. The weight percentages for each trial (A-D) were 54.0#%, 53.4#%, 54.1#%, and 53.##%, with an average of 53.## ± .5###%. It was also found that the four trials yielded calculations of 61#, 60#, 61#, and 61# mmol of C2O42- per 100g of complex analyzed. The averaged value, with the inclusion of two standard deviations, reported to be 61# ± 7.## mmol of C2O42- per 100g of complex analyzed. In 4C, Spectrophotometry was used to determine the iron content in the same iron (III) oxalate complex. The average weight percentages of Fe3+ for samples 3-5 of the unknowns were found to be 12.##%, 12.7#%, and 14.##%, with an average weight percentage of 13.09 ± 2.58%. The number of millimoles present in 100g of complex were found to be, for unknown samples 3-5: 215.### mmol Fe3+, 227.### mmol Fe3+, and 259.### mmol Fe3+, with an average of 23#.### ±4#.## mmol Fe3+ in every 100g of complex. This data was used, along with the data from 4A and 4C, to conclude that the empirical formula of the complex was K3[Fe(C2O4)3]·2H2O, and the experiment had a percent yield of 74.##%.

2. Introduction
The goal of the three experiments is to successfully synthesize an iron (III) oxalate compound and then further analyze it for oxalate (4B) and iron (4C) composition. A coordination compound is comprised of at least one complex ion, and a complex ion itself consists of two parts: a [transition] metal ion (which has a positive charge, making it an electron-deficient Lewis acid) and one or more ligands (molecules or anions usually of negative charge, rendering them electron-rich Lewis bases, through some neutral molecules such as H2O and NH3 work as well). In the union of the electron-deficient metal ion and the electron-rich ligand, the two species are said to “coordinate” to each other. The coordination number of the metal specifies the number of electron pairs which are donated to the metal center. Coordination numbers may vary, with 2, 4, and 6 being the most common.

Ligands themselves may vary in the number of available binding sites. Monodentate ligands are those which donate a single pair of electrons to the metal center. Hence, six monodentate ligands – such as H2O- bound to a center metal ion would result in a coordination number of six. “Chelate” and “multidentate” are the terms applied to ligands capable of binding at more than one site. Bidentate ligands (such as the oxalate ion C2O42- used in this experiment) bond at two sites on the center metal ion, and tridentate ligands (such as EDTA or ethylenediaminetetraacetato-) bind at three sites. The entire complex may have an overall charge that is positive, negative, or even neutral. Reduction-oxidation reactions (or redox, for short) are ones in which there is a change in the oxidation numbers of two or more reactant-product pairs. The oxidized component is said to lose electrons (i.e., Fe2+ is oxidized to...
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