[Win,odd Dhamnekar]

Is author's answer correct ?

My answer:

 [itex]K_{sp}  of PbCl_2=1.7e-5[/itex], So the 13.0 M of NaCl is needed, which is impossible to obtain.

[Orcio_87]

Difference comes from given data - 1,7 x 10^-5 and 1,0 x 10^-4 for K = [Pb][Cl]², and also that 20 ppb ≠ 1 x 10^-7 M.

I get that concentration of Cl^- should be bigger than 9,22  M for concentration of Pb+ lower than 2 x 10^-8 M.

[Borek]

20 ppb ≠ 1 x 10^-7 M.

Actually 1×10^-7 M is 20 ppb (perhaps more like 21).

[Orcio_87]

@Borek Sorry, my error.

Now that I found that concentration of Cl^- should be bigger than 13 M for Pb²⁺ smaller than 1 x 10^-7 M (with K = [Pb][Cl]² = 1,7 x 10^-5).

[mjc123]

There seem to be different values out there in the literature. For example, on the wikipedia page for PbCl₂, the quoted solubility and solubility product are inconsistent - 10.8 g/L implies K_sp = 2.85 x 10^-4 M³.