The chelate ZnQ22- exhibits a maximum absorption at 480 nm. When the chelating agent is present in at least a fivefold excess, the chelate's absorbance is dependent only upon the molar concentration of Zn(II) and obeys Beer's law over a large range. Neither Zn2+ nor Q2- absorbs at 480 nm. A solution that is 2.30×10-4 M in Zn2+ and 8.60×10-3 M in Q2- has an absorbance of 0.690 in a 1.00-cm cell at 480 nm. Under the same conditions, a solution that is 2.30×10-4 M in Zn2+ and 5.00×10-4 M in Q2- has an absorbance of 0.540. Calculate the formation constant for: Zn2+ + 2 Q2- ? ZnQ2