50.0 mL of a 0.00200 M Cd^2+ solution is titrated with 0.00400 M EDTA in the

presence of 0.0750 M NH3 buffered at pH = 9.00. Determine pCd^2+ when 28.5 mL of EDTA solution have been added.
Cd^2+ + Y^4- ? CdY^2- Kf= 3.16 x 10^16
Cd^2+ + NH3 ? CdNH3^2+ ß1 = 3.24 x 10^2
Cd^2+ + 2 NH3 ? Cd(NH3)2^2+ ß2 = 2.95 x 10^4
Cd^2+ + 3 NH3 ? Cd(NH3)3^2+ ß3 = 5.89 x 10^5
Cd^2+ + 4 NH3 ? Cd(NH3)4^2+ ß4 = 3.63 x 10^6
(alpha)aCd^2+ = 1.80 x 10^-3
(alpha)aY^4- = 0.041
Chemistry