Which of the following is insoluble in water?

Assign $A, B, C, D$ from the given type of reaction.
$ZnS(s) + 2HCl(aq) \longrightarrow ZnCl_2(aq) + H_2S(g)$

On adding $0.1 \ M$ solution each of $[Ag^+]$,$[Ba^{2+}]$,and $[Ca^{2+}]$ to a $Na_2SO_4$ solution,which species precipitates first? Given: $K_{sp}(BaSO_4) = 10^{-11}$,$K_{sp}(CaSO_4) = 10^{-6}$,$K_{sp}(Ag_2SO_4) = 10^{-5}$.

The solubility of $AgCl$ in its solution is $1.25 \times 10^{-5} \ mol \ dm^{-3}$. What is the solubility product of $AgCl$?

The compound insoluble in water is

Calculate the minimum concentration of sulphate ion required to precipitate $BaSO_4$ in a solution containing $10^{-4} \ mol/L$ of $Ba^{2+}$. $(K_{sp} \ BaSO_4 = 4 \times 10^{-10})$