A solution contains one or more of the following ions: Hg22+, Ba2+, and Fe2+. When potassium chloride is added to the solution, a precipitate forms. The precipitate is filtered off and potassium sulfate is added to the remaining solution, producing no precipitate. When potassium carbonate is added to the remaining solution, a precipitate occurs. Which ions were present in the original solution? Write net ionic equations for the formation of each of the precipitates observed.
The addition of KCl with Hg22+ will form a precipitate of Hg2Cl2 ,
This leaves you with Ba2+ and Fe2+ ions.
The Ba2+ ion should precipitate with the sulfate. Since it doesn't, there is no net ionic equation.
Thus the last ion is Fe2+ which form a precipitate with carbonate ion.
So the first net ionic equation:
Hg2 2+ (aq) + 2Cl- (aq)...