I have to consider that all Hg2+ reacted with S2-
Hg2+ + S2- ----> H2S
B 0,01 X 0
R -0,01 -0,01 +0,01
E 0 X-0,01 0,01
So I need 0,01 mol of S2-?
And I don't quite understand the part about the 99%, is it something like this:
KspBi2S3=[0,01x0,01]2+x[S2-]3
And I have to add the concentrations of S2- required to precipitate all mercury with the concentration that precipitates 99% of bismuth?