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Dousin12
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Homework Statement
To a saturated PbCl_2-solution there is a equally big volume of Pb(NO3)_2 added which has the concentration 0.05M. Is there a precipitation of PbCl2 or not? If Ks is 2,54*10^-4 for PbCl2.
The problem here is that I don't know how to find the concentration of Cl2 or Pb. My chem book said that u can solve 11g of PbCl2 per liter. So should I say that
11g/Molar mass ob PbCl2=0.04 moles <=> 0.04 moles Pb2+ <=> 0.08 Moles Cl-
But because there is 0.05M of Pb(NO3)_2 as well so the moles Pb is 0.04+0.05=0.09moles
But if i say:
[CL^-]^2*[Pb^2+]=[0.08]^2*[0.09] I get 5.76*10^-4 which is bigger than ks. But in the book they say:
[CL^-]^2*[Pb2+]=7.16*10^-5
How do they get that value?