I have a problem(4, page 25): Calculate the product of solubilty of PbCrO4
, if its solubilty in 1M AcOH is 2,9*105
Here's how I dealt with it: Ks=S2
, where S is the aparent solubility, and α the coefficients, defined as the raport of the species it denote and the total concentration (protonated, free, complexated etc) of the species.
I had to take into consideration the following equilibriums:
AcOH + Pb2+
2 AcOH + Pb2+
=6.5, we are also given pKaAcOH
I did the matter balance: S= [Pb2+
] + [PbAcO+
] , and also S= [CrO42-
]. Assuming the ph stays constant(PH=2.38, 1M AcOH solution),
I have obtained αCrO42-
, when it actually is ≈10-14
. Where am I wrong?