Practically, we can expect that solution is saturated when for prolonged time some solid phase exists in an equilibrium with solution of this solid.

So if I know ONLY that I have a saturated solutuion of PbSO4 5*10-4M can I say that [Pb

^{2+}]=[SO4

^{2-}]=5*10

^{-4} ??

Because I have this exercise:

Calculate the potential "E" of the cell:

Zn|ZnSO4 (5*10[sup-4[/sup]M ||PbSO4 (saturated) (5*10

^{-4}M |Pb

Now the nernst for E

_{Pb}= E(PbSO4/Pb+SO42-) + 0,059/2 * log 1/[SO

_{4}^{2-}]

But can I say that [SO

_{4}^{2-}] = 5*10

^{-4} , because I have a saturated solution of PbSO4 5*10

^{-4}M??

Thanks!!