Saturday, November 30, 2013

Determination of Zinc and Nickel Concentration by (1) Ion-Exchange Chromatography Followed by Chelometric Titration, and by (2) Atomic Absorption Spectroscopy of the Mixture

Determination of surface and plate note preoccupancy by (1) Ion-Ex castrate Chromatography Followed by Chelometric Titration, and by (2) Atomic Absorption Spectroscopy of the Mixture taste 4Dates of Experiment: 10/14/08 done 10/30/08Date of piece: 11/7/08Chem 2262LI. IntroductionIn this taste, the coat and plate contents of isolateds were well-tried using 2 methods. In the first method, nickel and zinc were separated by dint of and by dint of ion-ex miscellanea chromatography and canvas by chelometric titration. In the second method, the inexplicable was analyzed with the atomic preoccupation spectroscopy (AAS) of the mixture. In and ion-exchange column, the ions be separated cal research lable to their tendencies to interact with the fixed phase of the column. In this case, the anion-exchange resin is that fixed phase. atomic number 28 passed through the column unhinde ruby-red and therefore first. surface organize chlorozincate anions that reacted with th e resin. It could not pass through the column until a electroneutral aqueous answer was tally through. The elements were determined quantitatively by titration with ethylenediaminetetraacetic acid (EDTA). This method is value as a intimately estimate and is used wide because of its use of common lab equipment. Only a wizard column was emission for for each one metal in the fill of judgment of conviction. To acquire a nub for the effect that the method has on the outcome, one should split the savor into replicates before the column. However, this may displace the accuracy, reduce the precision, and increase the time of the abstract. In AAS, ions are laid-back-minded due to the wavelength of well-fixed emitted when atomized ions are passed through a flame. each element has a characteristic wavelength of light emitted. The instrument is gradatory using standard firmness of purposes preceding to passing samples through. The results are taken using a standardisatio n wave. This method is valued due to its ef! ficient speed, ease of use, elevated selectivity, accuracy, and precision. A disadvantage is that it requires a special piece of machinery to do the investigate. II. ProcedureIn order to prepare the ion-exchange column, frappe wool was placed preceding(prenominal) the s peakcock of a buret. cardinal to 40 milliliters (mL) of anion-exchange resin were added to the buret. A swear out of atomic number 6 mL of deuce molar HCl was passed through the column. The sample was prepared by adding 16 mL of concentrated HCl to 75 mL of singular solution and diluting that to light speed mL. The 30 mL sample was transferred to the crystalize of the column. Four hundred mL of two molar HCl were operate through the column after the sample at a rate of 5 mL a minute. altogether of the lap was collected in a 500 mL beaker. The beaker was replaced with some(a) other 500 mL beaker in order to beat the succeeding(prenominal) wash of 450 mL of deionized water. The first beaker contained the nickel sample. It was divided into third aliquots, and the liquid was evaporated. Each residue was dissolved in 100 mL of distilled water and mixed together. Approximately 10 mL of pH 10 buffer were added. The entire solution was thin out to 500 mL. Half a gram of murexide indication was added to the dilution. iii 50 mL aliquots were titrated with standardized EDTA until the glossary changed from discolor to yellow. all(a) data was preserve in elude 1. The second beaker contained the zinc sample. It was divided into three aliquots, and approximately five mL of pH 10 buffer were added to each beaker. Two flatten outs of Eriochrome B drop T indicator were added to each sample. Each was titrated against standardized EDTA until the color changed from red to blue. all told data was preserve in turn off 2. For AAS, two large samples were prepared. For nickel analysis, 33 mL of hidden solution were diluted to 50 mL. For zinc analysis, 2 mL of unexplored quantity solu tion were diluted to 50mL. Three standard solutions o! f 20, 40, and 60 separate per million (ppm) of nickel were run through the AAS instrument. All absorbencies were recorded in Table 3. A standardisation slue was do from that data (Figure 1). The solution for nickel analysis was run through the instrument for three tests. All absorbencies were recorded in Table 4. Three standard solutions of 1.2, 2.4, and 3.6 ppm of zinc were run through the AAS machine. All absorbencies were recorded in Table 5. A calibration curve for zinc was made from that data (Figure 2). The zinc analysis solution was run through the AAS for three tests. All absorbencies were recorded in Table 6. III. Data?Table 1: Titration of Nickel in 0.0100 M EDTAInitial mLFinal mLTotal mL0.001.1251.1251.502.601.102.603.701.10?Table 2: Titration of Zinc in 0.100 M EDTAInitial mLFinal mLTotal mL0.003.003.003.506.503.008.2011.703.50?Table 3: Standard Solutions of Nickel niggardness (ppm)Absorbance200.166400.280600.418?Table 4: unacknowledged Absorbencies of NiSampleAbsorb ance10.16920.16730.166?Table 5: Standard Solutions of ZincConcentration (ppm)Absorbance1.20.3522.40.4203.60.442?Table 6: terra incognita Absorbencies of ZnSampleAbsorbance10.38020.38630.384?Figure 1?Figure 2IV. Calculations?Concentration of Nickel as determine by EDTA TitrationoExample Calculations for Titration 1oTitration 2: 0.00489 MoTitration 3: 0.00489 M?Concentration of Zinc as hardened by EDTA TitrationoExample Calculations for Titration 1oTitration 2: 0.040 MoTitration 3: 0.047 M?Concentration of Nickel as Determined by AASoExample Calculations for Sample 1oSample 2: 0.00068 MoSample 3: 0.00067 M?Concentration of Zinc as Determined by AASoExample Calculations for Sample 1oSample 2: 0.00393 MoSample 3: 0.00392 M?Mean ConcentrationsoExample Calculations for Ni as Determined by AASoZn Determined by AAS: 0.00391 MoNi Determined by EDTA Titration: 0.
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00511 MoZn Determined by EDTA Titration: 0.0423 M?Standard DeviationoExample Calculations for Ni as Determined by AASoZn Determined by AAS: 0.000026oNi Determined by EDTA Titration: 0.00038oZn Determined by EDTA Titration: 0.004oBoth Ni Methods: 0.003oBoth Zn Methods: 0.038?RSDoExample Calculations for Ni as Determined by AASoZn Determined by AAS: 0.0066oNi Determined by EDTA Titration: 0.075oZn Determined by EDTA Titration: 0.0946?Percent breakoExample Calculations for Ni as Determined by AASoZn Determined by AAS: 223%oNi Determined by EDTA Titration: 69.6%oZn Determined by EDTA Titration: 231%V. mistake AnalysisIn this experiment, several sources of random and systematic shift presented themselves. Most of the error was encountered in the anion-exchange column and EDTA titration phase of the experiment. This was due to several uncertainties in the construction of the experiment. The ability of the resin to hold chlorozincate ions is unknown. It seems as though the resin could not contain these ions because the submergence of nickel obtained from the experiment was too senior high school. The presence of zinc in a nickel titration raises the equivalence point and gives a higher than actual denseness of nickel. Also in the EDTA titration, the murexide indicator never obtained the correct starting time color. Perhaps the equivalence point was reached earlier, but the color change was impossible to note with a purple color already present. Other sources of error throughout the experiment resulted from a insufficiency of proper equipment (i.e. pipettes for dilution measurements). VI. ConclusionDespite the lack of accuracy in the experiment, both methods presented were in truth precise. The expected concentration of nickel in the unknown was 0.00125 M. The concentra tion was determined to be 0.00068 M and 0.00153 M thr! ough EDTA titration and AAS respectively. The per centum errors for the values were 45.6% and 69.6% correspondingly. The expected concentration of zinc in the unknown was 0.00121 M. The concentration of zinc was determined to be 0.00391 M and 0.0423 M through EDTA titration and AAS respectively. The percent errors for the values were 223% and 231% in that order. The extremely high error indicates either poor techniques or a cruddy unknown. Due to the reproducibility (high precision) of the results, one may assume that it was and so a contaminated sample. VII. Works Cited?EDTA Titrations? (Chapter 12, pp. 228-249), Harris Quantitative Analytical Chemistry, seventh edition, 2007?Atomic Spectroscopy? (Chapter 21, pp. 453-473), Harris Quantitative Analytical Chemistry, 7th edition, 2007 If you percentage to get a full essay, order it on our website: OrderCustomPaper.com

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