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Experiment 1Spectrophotometric Determination of the Stability constantof a Complex IonStudent Name: Adam SadowskiStudent Number: 1000142071Other Member(s) of the Team: Kartik Moza Practical Section Number: 0122Date the Experiment was Performed: 16/01/2013Date the Report was Submitted: 25/01/2013Submitted to Dr. I-San Chan
2PurposeKnowing various stability constants is relevant to our safety and economy when consideringwhich solutions will react with and damage water-supplying drainage pipes; these constants arequantified representations of a reaction’s direction and extent when the concentrations of its ionsor gaseous atoms are not in equilibrium. Complex ions can be the products of mixing metal ions(as the Lewis acids) with ligands (as the Lewis bases). Transition metal cations, such as iron(III), can produce especially stable complex ions when reacted with ligands such as SCN-. In thisexperiment, ferric ions reacted with thiocyanate ions to form complex ions of one form:Fe+3(aq) + SCN-(aq) Fe(SCN)+2(aq)The above is a reversible equation omitting the water, whose concentration is nearly constant, and for which the stability constant is K = [Fe(SCN)+2]/[Fe+3][SCN-] .This constant has been determined in steps: 1) by mixing solutions with an excess of thiocyanateions and utilizing a spectrophotometer to acquire absorbance values for differing concentrationsof complex ion; 2) by mixing solutions without an excess of either reactant to thereby establish