Chemical Reaction and Precipitate Problem

Question

Which substance, Na2S, NaOH, K2SO4, or KI (all 1.0M) will form a black precipitate when allowed to react with 1.0M aqueous Pb (NO3) 2?

Answer 1

Na₂S would form a black precipitate with Pb(NO₃)₂.  The others will also form a precipitate with Pb(NO₃)₂, but PbS (lead sulfide) is the one that is black.

 

Na₂S(aq) + Pb(NO₃)₂ (aq) ===> 2NaNO₃(aq) + PbS(s)