CuCo Formal Lab Report

CuCo Formal Lab Report - Quantitative Analysis of a...

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Unformatted text preview: Quantitative Analysis of a Solution Containing Cobalt and Copper ABSTRACT The premise of this experiment was to become familiar with the techniques of ion exchange chromatography, complex titration, and atomic absorption spectroscopy. Under this premise, the purpose of this experiment was to determine quantities of cobalt and copper ions in a solution of unknown concentrations by using the above techniques. It was determined that 0.0996 mol/L of cobalt ions and 0.241 mol/L of copper ions were present in the original solution by using complex titration and atomic absorption spectroscopy, respectively. INTRODUCTION In order to quantitatively analyze a solution of unknown amounts of cobalt and copper ions, three techniques were used as previously mentioned. The first, ion exchange chromatography, allowed for the separation of the cobalt and copper ions. Ion exchange chromatography requires a column filled with ion exchange resins, which are insoluble and consist of cations and anions. When a solution containing ions are placed into the column, the cations and anions in the resins are exchanged with the ions in the solution. To be more detailed, the resins are composed of a framework of strong chemical bonds attached to positively or negatively charged functional groups that have an oppositely charged ion. These oppositely charged ions in the functional groups are replaced by the ions in the unknown solution, on a one to one ratio. This technique is suitable for this experiment as it is designed to separate ions and the components of the unknown solution being separated in this experiment are cobalt and copper ions. The second, complex titration, specifically the back titration of a solution containing the previously separated cobalt ions and a polydentate ligand known as EDTA with a standard solution of cobalt ions, allows for the determination of the moles of cobalt ion present in the original solution. Back titration is used over direct titration if either the reaction is too slow in one direction or if the reaction in a certain direction blocks the indicator, which shows when the endpoint occurs. The titrant used in the experiment contains a ligand, or a complexing agent. Ligands contain electron donating groups that form covalent bonds with metal ions in a solution to form coordination complexes. A polydentate ligand forms two more more bonds per ligand, and the one most often used to titrate metal ions is ethylenediaminetetraacetic acid, also known as EDTA. EDTA in excess of what is required to react with the cobalt ions of the unknown solution is added to the unknown solution of cobalt ions. When this solution is titrated with a standard solution of Co 2+ , the cobalt ions in the standard solution will react with the excess EDTA until the endpoint is reached. The moles of the cobalt ions in the unknown sample can therefore be calculated from the moles of EDTA and the moles of standard cobalt solution added. This technique is especially fitting for the quantitative analysis of cobalt because cobalt solution added....
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This note was uploaded on 09/19/2009 for the course CHEM 4B taught by Professor Moretto during the Spring '09 term at Berkeley.

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CuCo Formal Lab Report - Quantitative Analysis of a...

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