Absorption Spectroscopy

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Absorption Spectroscopy

And Beer’s Law

Odaro Osayimwen

October 14, 2012


1. Produce a 100.0mL of a .200M solution of the salt given by the Instructor: Calculate the weight needed. Weight the necessary amount of the salt on an analytical balance. Place weighted salt in a beaker and add about 50 mL of water, and stir until salt dissolves. Pour solution into a volumetric flask and dilute with until solution gets to the 100mL mark and mix well.

2. Obtain 2 spectrophotometer cells from instructor and fill the empty one with distilled water. Place it in the spectrophotometer and set the wavelength to 390nm (use this for reference), set the instruction to 100%T and calibrate. Take out the spectrophotometer cell and empty it. Now fill the spectrophotometer cell with a sample of the .200M solution and set the solution to 400nm and calibrate set the instruction to 100%T. Do this again but change the wave length to 10nm above the 390 to 600 range. Find the relative maximum from the graph.

3. Use a pipet to place 6mL, 4mL, 2mL, and 1mL of the .200 M solution into 4 clean test tubes. Dilute solution each test tube with enough water to reach the 8mL. Set the spectrophotometer wavelength to the max wavelength gotten from the graph. Rinse and fill the sample cell with one of the diluted solutions (from the test tubes). Place in the spectrophotometer and get the % T. Do this to all 4 test tubes, and the unknown solution given by the instructor.


Assigned salt Cobalt chloride (CoCl2*6H2O)

Mass of salt plus container 5.2671 +/-.0001 g

Mass of container .5179 +/-.0001 g

Concentration of standards

Solution Water

Standard 1 (6mL)

Initial .17 +/- .01 mL .11 +/- .01 mL

Final 6.01 +/- .01 mL 3.04 +/- .01 mL

Standard 2 (4mL)

Initial .98 +/- .01 mL...