Correction

3) Determining KFe (Gly)2+
A/ab = c  (.283 from solution 8)/ ((4545.45 mol-1 cm-1)*(1.1cm)) = 5.66x10-5 M
Therefore, x = 5.66x10-5 M = [Fe(SCN)2+]eq
Fe3+ SCN- FeSCN2+
I .0016 M .00032 M 0
C -X -X X
E (.0016 M – X) (.00032 M – X) (5.66X10-5 M)

Using equation 19.11: [SCN-]eq = CSCN – (A/ab) = (.00032 M – 5.66X10-5M) = 2.634x10-4 M
Using equation 19.12: [Fe3+]eq = [Fe(SCN)2+]eq / ( KFe(SCN)2+ * [SCN-]eq ) which equals
(5.66x10-5 M) /( (100)* (2.634x10-4 M) ) = .00214 M
Using equation 19.13: [Fe(Gly)2+]eq = Cm – [Fe(SCN)2+]eq – [Fe3+]eq which equals
(.0016 M) – (5.66x10-5 M) – (.00214 M) = 5.966x10-4 M
Using equation 19.14: [Gly-]eq = Cgly – [Fe(Gly)2+]eq = (.00032 M) – (5.966x10-4 M) = -2.766x10-4 M
Using equation 19.15: KFe(Gly)2+ = [Fe(Gly)2+]eq / ([Fe3+]eq * [Gly-]eq) which equals
(5.966x10-4 M) / ( (.00214 M)*(-2.766x10-4 M) = -1007.90

I still end up with a negative value, which resulted from equation 19.14, where at equilibrium, we had a bigger value for [Fe(Gly)2+]eq, compared to the Cgly (initial concentration of glycine). This could have resulted due to the fact that we had miscalculated the amount of glycine we measured into the solution, and we could have also misread the absorbance for the solution, which could have set the following equations that depended on the [FeSCN2+] to be wrong.


Sorry about this again. I really hope you understand. 

-Laayla M.T.