Colorimetric Determination for the Composition and Equilibrium Constant For the Formation of a Metal Complex Ion

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Colorimetric Determination for the Composition and Equilibrium Constant For the Formation of a Metal Complex Ion Abstract The object of this experiment was to determine properties for the formation of a metal complex ion, ferrothiocyanate by observing its colorimetric characteristics. The reaction was done for differing amounts of Fe+3 and SCN-, and the absorbance was measured using a spectrophotometer. The absorbance showed that maximum Fe(SCN)+2 ion production was achieved when the mole fraction of SCN was .6, which was close to the expected value of .5. However, when the equilibrium constant was calculated for this reaction, experimental error may have played a role when the achieved value of -660 was significantly different than an expected large positive number. These properties of equilibrium were determined through colorimetric properties. Introduction Colorimetric properties of certain chemical compounds can be used to determine many characteristics of the reaction itself. In this experiment, colorimetric determination was used to find the equilibrium constant for the formation of the Fe(SCN)+2 ion, noted by the equation Fe3+(aq) + SCN- (aq)  Fe(SCN)+2 Many chemical reactions such as this reaction are never fully completed in the sense that all the reactants will completely react to form the products. There exists a state known as equilibrium, in which neither the forward reaction nor the reverse reaction is performing. The equilibrium constant, K, is a measurement of the ratio of the concentrations of the reactants to products at which equilibrium is reached- the reaction will neither proceed in the forward nor reverse direction. In this experiment, the equilibrium constant is K= [Fe(SCN)+2] / [Fe... ... middle of paper ... ...esents itself that the actual experiment can’t be completed. If the equilibrium constant were to be calculated accurately, this could be used to calculate concentrations of various products or reactants. This experiment was completed with minor deviations from the original protocol. A slight mistake was made when solutions were transported from the test tube to the cuvette. The funnel wasn’t rinsed out completely, and this may have led to slight deviations. However, it may not have been enough to make a significant impact upon the results. Overall, this experiment went as planned. The equilibrium constant for this reaction was calculated, as well as finding the mole fraction at which this reaction would produce the most significant reaction. Even though some calculations weren’t as expected, this reaction was completed and made sense from a superficial view.

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