OBJECTIVE:

To determine the equilibrium constant for the following reaction:

Fe3+(aq) + SCN-(aq) -----> Fe(SCN)2+(aq)

BACKGROUND:

In this experiment, the equilibrium constant, K, for the above reaction is given by the expression:

K = [FeSCN 2+]

[Fe 3+][SCN 1-]

where the concentrations of the substances are those at equilibrium. The equilibrium concentrations of these substances will be determined and used to determine K.

Since the reactants are essentially colorless, whereas the complex ion product is deeply colored, a spectrophotometer will be used to determine the maximum absorbance due to the FeSCN2+at its four different concentrations. Beer's Law states that the absorbance of a colored solution is directly proportional to the concentration of the absorbing species. In this experiment, the FeSCN2+ is the absorbing species. The formula for Beer's Law is A = kc where A is the absorbance of the solution, k is the Beer's Law constant...