Cobalt forms a colored complex when a solution of cobalt(II) ions is mixed with a solution of ammonium thiocyanate. The color of the tetraisothiocyanatocobaltate(II) ion solution is a deep blue. A student determined 605 nm to be its analytical wavelength. To obtain a standard curve for his unknown analysis, the student prepared a series of six standard solutions by adding a quantity of 0.0500 M Co(NO3)2 to a 50 mL volumetric flask that contained 10 mL of 1.0 M ammonium thiocyanate and 10 mL of DI water. Distilled water was added to make the total volume of each solution 50.00 mL. The percent transmittance of each solution was read, using a blank that contained all of the same components as the sample solutions except for the cobalt(II) solution.
How would I find the concentration of [Co(SCN)4]2- , for stock solutions of 1.0,2.0,5.0,7.0,9.0, and 10.0 mL solutions?