AgCl + 2 NH3 --> Ag[(NH3)2]^+ + Cl^-
K for the rxn shown is Kf*Ksp
Kf*Ksp for AgCl is about 2.9E-3
Kf*Ksp for AgBr is about 8E-6
Kr*Ksp for AgI is about 2.4E-9
As we proceed from AgCl to AgI the Ksp and Krxn shifts smaller and smaller to the solubility of the AgBr is about 1000 less and that of AgI is about 1 million times smaller. Actually, AgBr is slightly soluble in dilute (6M NH3) but AgI is virtually insoluble.
K for AgCl at about 1E-3 is not that small; compare with H3PO4 with k1 - about that number. But AgI complex is so small that compares with Ka of HCN.
Why does AgCl dissolve in NH3 but AgBr and AgI don't?
KSP of AgCl = 1.8 x 10-10
KSP of AgBr = 5.0×10–13
KSP of AgI = 1.5 x 10-16
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