Question

A saturated solution of `PbBr_2` is prepared by dissolving the solid salt in water. The concentration of `Pb_2^+` in solution is found to be 0.0115 M. What is the Ksp for `PbBr_2`?

Answer 1

`K_(sp)=6.1xx10^-6`

Explanation:

We interrogate the solubility equilibrium.........

`PbBr_2(s) rightleftharpoonsPb^(2+) + 2Br^(-)`

Now `K_(sp)=[Pb^(2+)][Br^-]`.........And if we say that the solubility of `PbBr_2-=S`, then by stoichiometry........

`K_(sp)=[S][2S]^2=4S^3` (because `S=[Pb^(2+)]`, and `[Br^-]=2S`

`=4xx(0.0115)^3=6.1xx10^-6`.........

Can you define what is meant by a `"saturated solution......?"`