[Chaste]

Equilibria involved :
FeG⁺ + G^-  FeG₂ K₂ = 3.2 x 10³
G^- + H₂O  HG + OH^- K_b = 6.0 x 10^-5
G_- is the amino acid glycine.
Suppose that 0.050 mole of FeG₂ is dissolved in 1 litre of water.

Qns: Using activity coefficient, find FeG⁺ if the pH is fixed at 8.5 and the ionic strength is 0.10M. For FeG⁺, use gamma = 0.79. and for G_- use gamma = 0.782

My attempt at the question:

MBE 1 = 0.05 = [FeG⁺] + [FeG₂]
MBE 2 = [FeG⁺] = [HG] + [G^-]

the ionic strength being 0.1,

0.1 = 0.5 x [FeG⁺] + [G^-] + [H₃O⁺] + [OH_-]   ----- 1

and I'm stuck. I suppose I need to solve simultaneous equations. how do I make use of the pH and activity coefficients to resolve this question?

[Pradeep]

Can use debye-hukal law to relate the concentration and ionic strength.

[Chaste]

hi there, thanks for the contribution. The question has been there for a while and it has been solved.