Question

Solid Na2S is divided into 3 solutions with 0.10M Mn2+ 0.10 M Pb2+ and 0.10 M Fe2+ each.

Ksp:
MnS = 3.0 x 10 -14
PbS = 3.4 x 10 -28
FeS = 6.0 x 10-19.

Which will precipitate first?

Answer 1

The wording of this problem leaves much to be desired. As worded it makes absolutely no sense what-so-ever. I know what you mean but that's not what you are saying. IF you mean that you will be adding very very small granules of Na2S to each, one at a time, and you want to know which will ppt with the lowest amount of Na2S, then the answer is the one with the smallest Ksp. That will be PbS.

Answer 2

Thanks.