Which of the following is more soluble in ammonia?

The expression for solubility product of mercurous iodide $(Hg_2I_2)$ is

Why only $As^{3+}$ gets precipitated as $As_2S_3$ and not $Zn^{2+}$ as $ZnS$ when $H_2S$ is passed through an acidic solution containing $As^{3+}$ and $Zn^{2+}$?

The solubility product of lead bromide is $8 \times 10^{-5}$. If the salt is $80\%$ dissociated in a saturated solution,find the solubility of the salt.

The solubility product of $BaSO_4$ is $1.3 \times 10^{-9}$. The solubility of this salt in pure water will be

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 $BaCO_3 = 5.1 \times 10^{-9}$)