Experiment #4 Colorimetric Determination of an Equilibrium Constant in Aqueous Solution PDF

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lab 4...

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Experiment #4: Colorimetric Determination of an Equilibrium Constant in Aqueous Solution Purpose: To explore the idea of equilibrium through the determination of an equilibrium constant for a reaction in a solution. Procedure: Part A: Refer to page 57, 58, and 59. Label six 50.0mL flasks 1-6. Place 10.0mL of 0.20M Fe(NO3)3 solution into each flask, and then place 1,2,3,4, and 5 mL 2.00E-3 NaSCN solution into flasks 2-6. Add enough 0.10 nitric acid to make each flask volume 50.0mL. Invert the flask to mix the solution. Rinse a cuvette with solution 1 and then fill the cuvette. Place it in a spectrometer, set the wavelength to 447nm and adjust to zero absorbance. Rinse the second cuvette with solution 2 and measure the absorbance and transmittance of the solution. Repeat with solutions 3-6. Part B: Label six 18 x 150mm test tubes 1-6. Place 5.0mL of 2.0E-3M Fe(NO3)3 solution into each tube. Add 1,2,3,4, and 5 mL 2.0E-3M NaSCN solution to tubes 2-6 respectively. Add 5,4,3,2, and 1 mL of 0.1M HNO3 to tubes 1-6 respectively, with total volume equaling 10mL. Measure the absorbances and transmittances of each solution at 447nm. Calculate: Use the absorbances and transmittances to create a calibration curve, and determine the equilibrium constant of FeNCS2+ in each test tube. Cleanup: Dispose of solutions in the designated waste container, as they are acidic and mildly oxidizing....