The compound not soluble in acetic acid is

When $H_2S$ gas is passed through a mixture containing $Mn^{2+}$,$Ni^{2+}$,$Cu^{2+}$,and $Hg^{2+}$ ions in an acidic aqueous solution,which of the following will precipitate?

For which sparingly soluble salt is the relationship between $K_{sp}$ and $S$ (solubility) given by $S = (K_{sp} / 4)^{1/3}$?

Which of the following sulphides has the lowest solubility product?

In an aqueous solution,$SCN^-$,$Br^-$,$I^-$,and $Cl^-$ are present. Which will get precipitated first when $AgNO_3$ is added to the solution? Given that:
$K_{sp}(AgCl) = 1.2 \times 10^{-10}$,
$K_{sp}(AgI) = 1.7 \times 10^{-16}$,
$K_{sp}(AgSCN) = 7.1 \times 10^{-7}$,
$K_{sp}(AgBr) = 3.5 \times 10^{-13}$

Solid $Ba(NO_3)_2$ is gradually dissolved in $1.0 \times 10^{-4} \, M \, Na_2CO_3$ solution. At which concentration of $Ba^{2+}$ will the precipitation begin? $(K_{sp} \, BaCO_3 = 5.1 \times 10^{-9})$