The formation constant Kf is a measure of the equilibrium between the complex ion and its constituent ions. In this case, the equilibrium is between FeSCN2+ and Fe3+ and SCN-. The reaction can be represented as:Fe3+ + SCN- FeSCN2+The formation constant Kf is given by:Kf = [FeSCN2+] / [Fe3+] [SCN-] When the concentration of SCN- is reduced by 50%, the equilibrium will shift to maintain the value of Kf constant. This is because Kf is a constant value at a given temperature and does not change with the concentration of the reactants or products.Let's assume the initial concentrations of Fe3+ and SCN- are [Fe3+]_0 and [SCN-]_0, respectively. After reducing the concentration of SCN- by 50%, the new concentration of SCN- will be 0.5 [SCN-]_0.Now, let's denote the change in the concentration of FeSCN2+ as x. At equilibrium, the concentrations will be:[FeSCN2+] = x[Fe3+] = [Fe3+]_0 - x[SCN-] = 0.5 [SCN-]_0 - xSubstituting these values into the Kf expression:Kf = x / [Fe3+]_0 - x 0.5 [SCN-]_0 - x Since Kf remains constant, we can set the original Kf equal to the new Kf:2.0 10^5 = x / [Fe3+]_0 - x 0.5 [SCN-]_0 - x Unfortunately, without knowing the initial concentrations of Fe3+ and SCN-, we cannot solve for the exact value of x. However, it is important to note that the value of Kf will remain constant at 2.0 10^5, even when the concentration of SCN- is reduced by 50%. The equilibrium will shift to form more FeSCN2+ to maintain this constant value.