Determine the concentration of the free nickel (II) ion in a solution in which the equilibrium concentration of free ethylenediamine is 0.400 molar, and that of the nickel complex above is 0.0100 molar? The formation constant for the tries (ethylenediammine) nickel (II)complex ion, [Ni(en)3]2+, is 4.1 x1017.