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Absorption Spectroscopy Identify Concentration of Two Cobalt Solution

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Absorption Spectroscopy of Unknowns
Purpose: To identify the concentrations of two cobalt solutions.
Procedure:
Obtain a Stock solution of Cobalt, and make three (3) dilutions for use in a set of standards.
Using an approximately 0.5M Stock Solution prepare three standards approximately (0.2M, .1M,
and 0.05M). In conjunction with a blank at 0M prepare a calibration curve.
1. Obtain several milliliters of distilled/deionized water in a clean small beaker
2. Obtain a three (3) clean, dry 25.00-mL volumetric flasks
3. Using a pipet, take necessary aliquots to prepare the Standard solutions, and dilute all to
25mL
4. Thoroughly mix all three dilutions and set aside.
5. Obtain an unknown
Set up the spectrometer and set to the specified wavelength
1. Obtain a cuvette and perform a blank using distilled water (0M), Calibrate the
spectrometer so that the absorbance of the blank is “0”
2. After emptying the cuvette poor a small aliquot of the lowest concentration solution and
place it in the spectrometer, record its absorbance.
3. Repeat this for each of the other standards and the stock solution. Absorbances for the
concentrations should go up with respect to concentration.
The incident light Io passes through the sample, the more particles present, the higher the
absorption of the energy will be, the transmitted light will be the remaining light that reaches the
detector. The instrument will measure the difference between the incident light and the
transmitted light, which will be a function of concentration.
4. Once the absorbance of the blank, three standards and stock solution have been recorded,
record the absorbance of the unknown solution.
5. Enter data into the class data set

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Since this is group lab no individual calibration curve will be conducted. Though your data can
be validated individually and should look similar to the following calibration curve:
Data:
Section A RAW DATA
In the data table you will find the stock solution concentration of 0.42M. Three dilutions were
made from the stock solution (A, B, and C) the volume of the stock solution used is listed for
each solution. The total volume is 25mL. The Absorbance of the Unknown is also given in this
section as no calculations were required obtain it.
Section B
The Calculated concentrations of each dilution are provided here. These values make up the
calibration curve (X Axis)
Section C
The absorbance of each solution of the calibration curve is provided here. These values make up
the calibration curve (Y Axis)
Section D
The Calibration curve data is given here, all values are calculated in excel rather than plotted on
a physical graph. The slope (m), the intercept (B) and R-squared value (evaluation of how linear
the data set is) With the absorbance of the unknown (Y Value) the X Value of the Unknown
Concentration could be calculated. The equation for a line is Y = mX + B.

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Absorption Spectroscopy of Unknowns Purpose: To identify the concentrations of two cobalt solutions. Procedure: Obtain a Stock solution of Cobalt, and make three (3) dilutions for use in a set of standards. Using an approximately 0.5M Stock Solution prepare three standards approximately (0.2M, .1M, and 0.05M). In conjunction with a blank at 0M prepare a calibration curve. 1. Obtain several milliliters of distilled/deionized water in a clean small beaker 2. Obtain a three (3) clean, dry 25.00-mL volumetric flasks 3. Using a pipet, take necessary aliquots to prepare the Standard solutions, and dilute all to 25mL 4. Thoroughly mix all three dilutions and set aside. 5. Obtain an unknown Set up the spectrometer and set to the specified wavelength 1. Obtain a cuvette and perform a blank using distilled water (0M), Calibrate the spectrometer so that the absorbance of the blank is “0” 2. Af ...
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