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Chemistry Forums for Students => High School Chemistry Forum => Topic started by: xshadow on February 17, 2017, 06:53:51 PM

Title: saturated solution
Post by: xshadow on February 17, 2017, 06:53:51 PM
I don't  understand its meaning....

A saturated solution is a solution with  also a precipitate??
Or only a solution without precipitate and with  Q = ks ??

For example if I know that I have a saturated solutuion of PbSO4 5*10-4 M , can i say that
[Pb2+] is 5*10^-4 ??
(that is equal to say that in a saturated solution all the salt(s) ,here PbSO4 5*10-4M, is dissociated...


Thanks!!!!!!
Title: Re: saturated solution
Post by: AWK on February 17, 2017, 07:13:52 PM
Practically, we can expect that solution is saturated when for prolonged time some solid phase exists in an equilibrium with solution of this solid.
Title: Re: saturated solution
Post by: xshadow on February 17, 2017, 07:33:17 PM
Quote from: AWK on February 17, 2017, 07:13:52 PM
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 [Pb2+]=[SO42-]=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*10-4M |Pb

Now the nernst for EPb= E(PbSO4/Pb+SO42-) + 0,059/2 * log 1/[SO42-]

But can I say that [SO42-] = 5*10-4 , because I have a saturated solution of PbSO4  5*10-4M??

Thanks!!
Title: Re: saturated solution
Post by: AWK on February 17, 2017, 09:03:20 PM
Quote
But can I say that [SO42-] = 5*10-4 , because I have a saturated solution of PbSO4  5*10-4M??
It depends on stoichiometry of compounds. Let's take Ag2SO4. Saturated solution is 0.0144 M and concentration of sulfate is the same but concentration of Ag+ is 2 times greater.