Which of the following is insoluble in water?

The solubility of salt $BA_2$ is $4 \times 10^{-4} \ mol \ dm^{-3}$. What is the solubility product of the salt?

Solid $Ba(NO_3)_2$ is gradually added to a $1.0 \times 10^{-4} \, M \, Na_2CO_3$ solution. At what concentration of $Ba^{2+}$ will precipitation start? (Given $K_{sp}$ for $BaCO_3 = 5.1 \times 10^{-9}$)

Assign $A$,$B$,$C$,$D$ from the given type of reaction.
$Ba(AcO)_2 + K_2CrO_4 \longrightarrow BaCrO_4 \downarrow + 2AcOK$

The solubility of silver chromate in $0.01 \, M$ $K_2CrO_4$ is $2 \times 10^{-8} \, mol \, dm^{-3}$. The solubility product of silver chromate will be

At $25^{\circ}C$,the solubility product $(K_{sp})$ of $Zn(OH)_2$ is $10^{-14}$. If $NH_4OH$ is $50\%$ dissociated,what will be the concentration of zinc in a $0.1 \ M$ $NH_4OH$ solution?