The Determination of Keq for FeSCN2+

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The Determination of Keq for FeSCN2+ Purpose: To determine the equilibrium constant Procedure: Part I - Preparing the solution 1)Get 10 test tubes 2)Prep the 5 reference solution test tubes. Mix each solutions using a stirring rod. Standard Volume of .200M Fe(NO3)2 Volume of .00020M KSCN solution Reference Solution #1 8.0mL 2.0mL Reference Solution #2 7.0mL 3.0mL Reference Solution #3 6.0mL 4.0mL Reference Solution #4 5.0mL 5.0mL Reference Solution #5 4.0mL 6.0mL 3)Using he burets transfer the appropriate volumes of each reagent to make the test solutions. Sample .0020M Fe(NO3)2 .0020M KSCN Distilled Water Test Solution #6 5.0mL 1.0mL 4.0mL Test Solution #7 5.0mL 2.0mL 3.0mL Test Solution #8 5.0mL 3.0mL 2.0mL Test Solution #9 5.0mL 4.0mL 1.0mL Test Solution #10 5.0mL 5.0mL 0mL 4) Mix each solution using a stirring rod 5)Measure the temperature of one of the solutions and record. Part II - Spectral Analysis 1)Ensure that the instrument has had time to warm up for 15 min. 2)Set the wavelength to 450 nm. Set the percent transmittance to zero. 3)With distilled water in the cuvet, place the cuvet into the spectrophotometer. Adjust the percent transmittance to 100% 4)our out the water in the cuvet, and fill with 2/3 of the reference solution. Read and record absorbance data. Read from lower concentration to higher concentration. 5)Continue to collect absorbance data for al reference and test solutions 6)Dispose of the contents of the cuvets. Data Tables #1 Reference Solutions for the Calibration Curve Sample [FeSCN2+] Absorbance Reference Solution #1 4x10-5 .2034 Reference Solution #2 6x10-5 .3028 Reference Solution #3 8x10-5 .3915 Reference Solution #4 1.0x10-4 .4908 Reference Solution #5 1.2x10-4 .5768 #2 Test Solutions Temperature - 21.9°C Sample [Fe3+] [SCN-] Absorbance Test Solution #6 1.0x10-3 2.0x10-4 .1002 Test

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