Determining of the equilibrium constant for the formation of FeSCN2+

General Chemistry II
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+

Data presentations and analysis
Table 1. Absorbances vs. concentrations of Beer’s law plot
Volume of 0.10 Fe3+ 0.10
Volume of 0.0020 M SCN-
Volume of water Concentration of SCN-
Concentration of Fe(SCN)2+
Optical absorbance
2.00E+00
3.00E-01
7.00E-01
2.00E-04
2.00E-04
6.00E-02
2.00E+00
5.00E-01
5.00E-01
3.30E-04
3.30E-04
1.52E-01
2.00E+00
7.00E-01
3.00E-01
4.70E-04
4.70E-04
2.37E-01
2.00E+00
1.00E+00
0.00E+00
6.70E-04
6.70E-04
3.47E-01
0.00E+00
0.00E+00
3.00E+00
0
0
0.00E+00

Figure 1. Optical absorbance Beer’s law plot

Table 2. Part b. trials and concentrations
Volume of 0.006 M Fe+3 (mL)
Volume of 0.0020 M SCN- (mL)
Volume of water (mL)
Initial Concentration of Fe+3 (M)
Initial Concentration of SCN- (M)
Equilibrium Concentration of Fe(SCN)2+ (M)
Optical absorbance
1.70E+00
7.00E-01
6.00E-01
3.40E-03
4.67E-04
8.97E-05
2.80E-02
2.00E+00
4.00E-01
6.00E-01
4.00E-03
2.67E-04
1.21E-04