Question

Fe (aq)SCN-(aq) FeSCN (aq) thiocyanate iron(II) thiocyanoiron(il) Introduction When the reactants shown above, are combined, chemical equilibrium is reached rapidly. Once equilibrium is established, the equilibrium constant can be calculated if the concentration of all the ions are known: [FeSCNP.he [SCN-... and (Feng Your task is to prepare three different equilibrium systems that contain different concentrations of these ions. Keep in mind that although the concentrations will be different, the value of the equilibrium constant Ke will be indeed constant The FeSCN ion has a characteristic red color. The concentration of this ion can be ermined by using a spectrometer. Since the solution is red, t will absorb blue light Therefore, we set the wavelength of light to a blue setting (447 nm) on the spectrometer. Since only FeSCN2+ absorbs blue light, the absorbance of the equilibrium proportional to [FeSCN2%g. By mea suring the solution, Ass, you can determine [FeSCNP Jea. The standard solution of FeSCN2 has a known concentration. According to Beer's Law Absorbance, A ebc, where A is the absorbance, e is the molar absorptivity, b is the path length (in cm) and c is the molar concentration of the sample. Because and b are constants for this experiment, the FeSCN2 lee and absorbance are directly proportional. Therefore, the concentration of FeSCN2 for any of the equilibria can be found by Once the [FeSCN2%q is determined, you can calculate the concentrations of the other two ions at equilibrium from mass balance. Note that the coefficients in the equation above are 1. Therefore, the concentration of the other two ions is given by the following equations: Fe3 (aq) SCN-(aq) FeSCN2 (aq) Initial 0.00 M Change [FeSCN2 Joq (from ratio above) Equilibrium Conc'ns

Answer 1

Initial Concentration of Fe3+ and SCN- are to be provided for the calculation of equilibrium concentration.

ICE tables will help you determine these values. Initial amounts, changes in amounts, and final equilibrium amounts are shown. These values must be in moles/L.

• initial amounts of reactants (amounts before the reaction begins): determined using the dilution equation

  • To find the initial concentration of SCN^–, use the dilution equation: (M₁V₁)/V₂ = M₂, where

    V₂ = 10 mL.

  • To find the initial concentration of Fe³⁺, use the dilution equation: (M₁V₁)/V₂ = M₂, where V₂ = 10 mL.

• initial amount of product (the amount before the reaction begins): zero

• equilibrium concentration of product ([FeSCN²⁺]_eq): determined spectroscopically

[FeSCN²⁺] at equilibrium is determined using Beer's Law; x is the amount of FeSCN²⁺ created (determined experimentally).