how wud u prepare 1L of a 1.30M aqueous solution of barium sulfide
explain
Theoretically I would do it this way.
You want how many mols? That's M x L = mols.
Then mols = grams/molar mass. You have molar mass and mols, solve for grams.
Place that many grams in a 1L volumetric flask, add some water, swirl until dissolved, then make to the mark with distilled water and mix thoroughly.
NOTE: Having said all of that, this won't work because BaS is so insoluble. You simply will not dissolve that much BaS in 1 L of water. You could add some HCl to it to make it dissolve and that will do it; however, that will evolve most if not all of the sulfide ion as H2S and you will have 1.30M BaCl2 and not BaS. My best guess is that this is a made up problem to see how it's done and the author of the problem didn't know enough chemistry to realize that BaS is not soluble.