Lab 3 - Solutions and Spectroscopy

Lab 3 Solutions and Spectroscopy

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Unformatted text preview: at can be used in reporting concentration. Usually, four significant figures are used. The second common way to make a solution is to dilute a stock www.webassig encheml1/lab_3/manual.html 2/7 4/15/13 Lab 3 - Solutions and Spectr oscopy solution with additional solvent. The relationship between the concentrations and volumes of the concentrated and diluted solutions is, (2) CiVi = CfVf where Ci and Vi are the concentration and volume of the initial (concentrated) solution and Cf and Vf are the concentration and volume of the final (diluted) solution. The accuracy with which you measure volumes determines the number of significant figures you can use in reporting your concentration. Any error in the concentration of the stock solution (Ci) will be propagated into the concentration of the dilute solution (Cf). For this experiment, assume that you are working at a company that uses copper(II) ion solutions in its processing. The production manager has sent you a small sample of the copper(II) ion solution they use and told you to make more at that specific concentration. Unfortunately, the production manager did not tell you what the concentration was, and she just left for vacation. Your job is to determine the concentration of the solution, and to generate more solution of that same concentration. In Part A of this experiment, you will make several solutions with known concentrations of copper(II) ions, then make absorbance measurements on them, and develop a calibration curve. You will then measure the absorbance of the unknown solution and determine its concentration from that calibration curve. In Part B, you will make a copper(II) ion solution with a concentration identical to the unknown by dissolving solid copper sulfate, CuSO4 · 5 H2O, in water. In Part C, you will make a copper(II) ion solution with a concentration identical to the unknown by diluting a concentrated, stock copper sulfate, CuSO4, solution. You will compare the accuracy with which you can make the solutions by the two methods. Equipment 1 MicroLab Spectrophotometer 1 MicroLab Spectrophotometer Instruction Sheet 6 vials 2 Serological pipets 1 pipet bulb 5 13 × 100 mm test tubes 5 stoppers 1 test tube rack 2 30 mL beakers 2 25 mL volumetric flasks w/ stoppers 1 250 mL beaker for copper waste 2 eye droppers Reagents 25 mL 0.5XX M CuSO4(aq) stock solution 10 mL CuSO4(aq) unknown solution 1 g solid CuSO4 · 5 H2O Safety www.webassig...
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This document was uploaded on 01/22/2014.

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