Determining of the equilibrium constant for the formation of FeSCN2+ Introduction The objective of this experiment was to determine the equilibrium concentration and then determine Kc. A dilution calculation was formed to determine the concentration of SCN- and Fe(SCN)2+. Each cuvette was filled to the same volume and can be seen in table 1. Then the absorbances were recorded from each cuvette and can be seen in table
1. A Beer’s law plot was made from the data that was recorded from the optical absorbance. During the second part of the experiment Fe (NO3)3 was added and diluted with HNO3 . All of the cuvettes were mixed with the same solutions in the second part of the experiment, which can be seen in table 2. A dilution calculation was made to determine the initial concentration of Fe3+and SCN-. Then the formula Abs + b/ slope was used to determine the equilibrium concentration which lead to the calculation of each Kc per trial. Chemical reaction
Fe3+ + SCN- FeSCN2+
An acid and a base were mixed together throughout the experiment, which resulted in a bright orange color. It was determined that using the colorimeter at 565nm the would give the optimum wavelength because it was the closest absorbance to 430nm. All of the cuvettes were filled to 3mL so there would not be another dependent variable. Whenever Fe3+ would come in contact with SCN- there would be a color change. Relatively all of the Kc were close to each other as they should be because the only variable that affects a change Kc and the temperature was kept consent throughout the experiment. The average Kc from all five trials is 1.52 x 10 2.