water project final lab report

water project final lab report - Introduction Water quality...

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Introduction Water quality is an important issue, noting that normal tap water has different ionic content, although thought to be pure by many. In this experiment, the intent is on testing the ionic contents and concentrations of tap water obtained from sinks in several different locations throughout Tucson. Four different tap water samples located throughout Tucson will be measured for ionic content. Two samples of tap water will be collected from different areas located on the University of Arizona campus (Well #4) to compare and contrast the ionic content for a similar location. The other two samples will be obtained from the eastside of Tucson (Well #6) and the westside of Tucson (Well #3). This experiment deals with determining the quality of water by using the techniques of complexometric titration, ion exchange chromatography, potentiometry and flame photometry. This experiment is intended to determine the total divalent metal ion concentration using a complexometric titration, to determine the total ionic content using ion exchange chromatography, to determine the [Ca 2+ ] using an ion selective electrode, and to evaluate a series of samples for ionic content. Complexometric titration is a volumetric technique for determining the amount of a particular material present in a sample. It is commonly used to measure the number of metal cations present in a solution, as well as to determine “water hardness”, which is a measure of the amount of divalent metal cations, primarily Ca 2+ and Mg 2+ present in the solution. The higher the concentration of these ions, the harder the water is considered to be. The technique of complexometric titration will allow the determination of total divalent and trivalent metal ion contents, as well as the molarity of Ca 2+ and Mg 2+ . In this case, the trivalent metal ions were assumed to be none and were, therefore, not assessed. This technique involves a common complexing agent, ethylenediaminetetraacetic acid, H 4 EDTA, which will be diluted to 3 different concentrations. For each titration trial, the concentration of divalent metal cations as both molarity and as parts-per-million (ppm) will be determined. The concentration of [M 2+ ] can be determined by the following equation: [M 2+ ] = moles M 2+ /sample volume, where moles M 2+ = moles EDTA used. The parts-per-million (water hardness) can be determined by the following equation: ppm = mass of component/mass of sample x 10 6 , where all divalent ions are assumed to be calcium ions, therefore assumed there were trivalent cations present, and the concentration of divalent cation is converted according to the equation units (Brown, 182). An indicator is used throughout this experiment which forms a complex that has a different color than the free ion, allowing the chemical change to be visibly determined (Brown, 178). This indicator is Eriochrome Black T (ErioT), a triprotic acid. Total ionic content, pH, dissolved acids, organics, and water hardness are common measures of
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This note was uploaded on 04/02/2008 for the course CHEM 104B taught by Professor Staff during the Spring '07 term at Arizona.

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water project final lab report - Introduction Water quality...

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