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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 n.net/ebooks/wsug 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,
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
2 Serological pipets
1 pipet bulb
5 13 × 100 mm test tubes
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
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This document was uploaded on 01/22/2014.
- Spring '14