The correct answer is (B) lead(II) sulfide.
In this scenario, the compound that precipitates first would depend on the solubility of the respective sulfides.
Generally, metal sulfides have varying solubilities in water, with some being more soluble than others. Based on the solubility rules, we can determine the compound that precipitates first:
(A) Cobalt sulfide (CoS): Cobalt sulfide has low solubility in water, so it has the potential to precipitate.
(B) Lead(II) sulfide (PbS): Lead(II) sulfide has very low solubility in water, making it highly likely to precipitate.
(C) Nickel sulfide (NiS): Nickel sulfide has moderate solubility, so it may not precipitate as readily as lead(II) sulfide.
(D) Zinc sulfide (ZnS): Zinc sulfide has relatively low solubility, so it could potentially precipitate.
(E) Sodium sulfide (Na2S): Sodium sulfide is highly soluble in water and will remain in solution.
Based on their respective solubilities, lead(II) sulfide (B) is likely to precipitate first, followed by cobalt sulfide (A), zinc sulfide (D), and nickel sulfide (C). Sodium sulfide (E) will remain in solution.
Therefore, the correct answer is (B) lead(II) sulfide.