Determining Equilibrium Constant: Spectrometric Analysis of FSCN2+

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The lab used spectrometric analysis to determine the molar absorptivity and the equilibrium concentration of FSCN2+. With these data, the equilibrium constant for the reaction between the Fe(III) ion and thiocyanic acid was calculated. Introduction: The purpose of this was lab to use Beer’s Law to measure the equilibrium concentrations of FSCN2+ and to use that measurement to determine the equilibrium constant for the reaction. In a reversible reaction, the concentrations of reactants and products oscillate continually until equilibrium is reached. Ongoing research is being conducting regarding equilibrium reactions. One area focuses on drugs targeting biological equilibrium reactions1. Barring external disturbances, once a system reaches equilibrium, it stays at equilibrium. The general form of a reversible reaction is written below: Initially, the concentration of the reagents decreases. As the concentration decreases, the rate of the forward reaction slows down. Meanwhile, the rate of the reverse reaction continually increases. Eventually, the rate of the forward reaction will equal the rate of the reverse reaction, and even though the reaction is still occurring, the change in concentration is insignificant. The equilibrium expression for the general reaction (1) is shown below:Keq is a value that is only dependent on temperature. If A, B, C, and D are mixed at unknown concentrations, the reagents will continuously react until equation (2) is true. The equation for the reaction between iron(III) and thiocyanic acid is shown below:The equilibrium constant of a reaction can …show more content…

Each trial is reacted and measured in the spectrometer before the next trial is reacted. Next, for Part B, “Equilibrium Measurements,” Fe3+ is reacted with thiocyanic acid and nitric acid according to the data in Table 2 across five trials. The initial concentrations of iron(III) ion and thiocyanic acid are noted in Table

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