Determination of surface and nickel note preoccupancy by (1) Ion-Ex modify Chromatography Followed by Chelometric Titration, and by (2) Atomic Absorption Spectroscopy of the Mixture essay 4Dates of Experiment: 10/14/08 done 10/30/08Date of score: 11/7/08Chem 2262LI. IntroductionIn this taste, the zinc and plate contents of isolateds were well-tried using 2 methods. In the first method, nickel and zinc were separated by dint of and with ion-ex stir chromatography and canvas finished with(predicate) chelometric titration. In the second method, the inexplicable was analyzed through the atomic tightness spectroscopy (AAS) of the mixture. In and ion-exchange column, the ions be separated cal science lable to their tendencies to move with the fixed phase of the column. In this case, the anion-exchange resin is that fixed phase. plate passed through the column unhinde ruby-red and therefore first. zinc organise chlorozincate anions that reacted with the resin. It could not pass through the column until a neutral aqueous answer was tally through. The elements were determined quantitatively by titration with ethylenediaminetetraacetic acid (EDTA). This method is value as a smashing estimate and is used wide because of its use of common lab equipment. Only a wizard column was crusade for each metal in the fill of cartridge holder. To acquire a moment for the effect that the method has on the outcome, one should split the consume into replicates before the column. However, this may displace the accuracy, reduce the precision, and increase the time of the summary. In AAS, ions are laid-back-minded due to the wavelength of clear up 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 antecedent to passing samples through. The results are taken using a normalization wave. This method is valued due to its efficient speed, ease of use, gradua! te(prenominal) selectivity, accuracy, and precision. A disadvantage is that it requires a special piece of machinery to do the try. II. ProcedureIn order to prepare the ion-exchange column, frappe wool was placed in high spiritser up 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 queer solution and diluting that to degree Celsius mL. The 30 mL sample was transferred to the blow over of the column. Four hundred mL of two molar HCl were armed service through the column after the sample at a rate of 5 mL a minute. altogether of the gargle was collected in a 500 mL beaker. The beaker was replaced with well-nigh other 500 mL beaker in order to bugger off the succeeding(prenominal) wash of 450 mL of deionized water. The first beaker contained the nickel sam ple. It was divided into common chord 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 unconvincing out to 500 mL. Half a gram of murexide index number was added to the dilution. iii 50 mL aliquots were titrated with standardized EDTA until the touch changed from purpurate 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 neglects 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. every last(predicate) data was save in circuit board 2. For AAS, two large samples were prepared. For nickel analysis, 33 mL of unidentified solution were diluted to 50 mL. For zinc analysis, 2 mL of unexplor ed solution were diluted to 50mL. Three standard solu! tions of 20, 40, and 60 separate per million (ppm) of nickel were run through the AAS instrument. All absorbencies were recorded in Table 3. A calibration thin 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 engrossment (ppm)Absorbance200.166400.280600.418?Table 4: unacknowledged Absorbencies of NiSampleAbso rbance10.16920.16730.166?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 resolved 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.
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. misunderstanding AnalysisIn this experiment, several sources of random and systematic wrongdoing 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 t he construction of the experiment. The ability of the resin to hold chlorozincate ions is enigmatical. It seems as though the resin could not contain these ions because the submergence of nickel obtained from the experiment was too high. The presence of zinc in a nickel titration raises the equivalence point and gives a higher than actual constriction of nickel. Also in the EDTA titration, the murexide indicator never obtained the correct graduation 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 deficiency 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 concentration was determined to be 0.00068 M and 0.00153 M through EDTA titratio n and AAS respectively. The per centum errors for th! e 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 therefore a contaminated sample. VII. Works Cited?EDTA Titrations? (Chapter 12, pp. 228-249), Harris Quantitative Analytical Chemistry, 7th edition, 2007?Atomic Spectroscopy? (Chapter 21, pp. 453-473), Harris Quantitative Analytical Chemistry, 7th edition, 2007 If you mess to get a full essay, order it on our website:
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