We will use several different initial concentrations of the reactants to determine whether the equilibrium constant has the same numerical value when the … Adding Two or More Equations. Any help would be appreciated. Test solutions of SCN − of unknown molar concentration. Value of K, the Equilibrium Constant . Using the absorbance … This question hasn't been answered yet Ask an expert. 13 Calculations: Part B - Equilibrium concentration of Fe(SCN)2+ - For Solutions 8 – 12, [Fe(SCN)2+] is determined from the calibration curve. In this experiment, the chemical reaction Fe 3+ (aq) + SCN – (aq) ß à FeSCN 2+ (aq) was studied to determine the equilibrium constant, K c. To determine this value, the absorptivity of several solutions were recorded using a colorimeter. You will prepare four equilibrium systems containing different concentrations of these three ions. The reaction is represented by the following equation: Fe 3+ + SCN – <—-> FeSCN 2+. Purpose. Most chemical reactions are reversible, and at certain conditions the rate of forward reaction and reverse reaction can be the same. In Part A of this experiment, you will prepare FeSCN 2+ solutions of known concentrations, measure their absorbances at 470 nm, and produce a calibration curve. . Thanks. Looking at Table 5, it is noticed that when [SCN-] 0 is increased, [SCN-]eq increased, [Fe3+]eq decreased and [FeSCN2+]]eq increased, confirming that the equilibrium constant should not change. It is also unaffected by a change in pressure or whether or not you are using a catalyst. 2. The absorbance in then put into Beer-Lambert’s law, A = εbc, to find concentration and ultimately the equilibrium constant. Top. In each beaker, there is an extreme excess of Fe3+ which forces the equilibrium far enough to the right that the [SCN–] can be assumed to be near zero and the [Fe3+] as remained essentially unchanged. These values are used to determine the equilibrium concentrations and equi- librium constant for the reaction. Calculating Equilibrium Constant Values Learning Objectives. What is the accepted value of the equilibrium constant of Fe(SCN)2+ (ten bucks says you won't find it)? There are some circumstances in which, given some initial amounts and the K eq, you will have to determine the concentrations of all species when equilibrium is achieved. The actual concentration of the FeSCN 2+ complex present at equilibrium in a solution may be obtained by comparing its color with standard solution, in which the concentration of FeSCN 2+ is known. Remember that your pathlength (b) is 1 cm for the Spec-20. Frank and Oswalt report a molar absorptivity (ε) for FeSCN2+ of 4700L/(mol*cm). K 1, K 2, etc. Using this value, I used the equation for the K constant of an equilibrium: $$\mathrm{K} = \frac{[\ce{FeSCN^2+}]}{[\ce{Fe^3+}][\ce{SCN^-}]}$$ $$\mathrm{K} = \frac{\pu{6.39e-5}}{0.002^2}$$ $$\mathrm{K} = 15.975$$ This did not turn out to be the correct answer, but I'm not sure why. The equilibrium constant expression Kc for Reaction is kc=FeSCN2+[H+]Fe3++[HSCN] Procedure *Preparation of the Beer’s law plot Prepare five solutions of FeSCN2+(aq) of known concentrations between 1x10-5M and 1x10-4M by diluting various volumes of 4.62x10-4 HSCN. Remember that your pathlength (b) is 1 cm for the Spec-20. Experimentally, the average constant K Introduction. 2. constant, ε, for FeSCN+2 by measuring its absorbance at different known concentrations of FeSCN2+. To determine the value of K eq, you must prepare a series of solutions, each of which contains known initial concentrations of Fe3+ (aq) and SCN − (aq) ions. 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