Which of the following is more soluble in ammonia?

The solubility product of $CaCO_3$ is $5 \times 10^{-9}$. Its solubility is equal to .......

The solubility product of $PbCl_2$ at $298 \ K$ is $1 \times 10^{-6}$. Its solubility in $mol/L$ is:

The compound insoluble in water is

Solubility product of a salt $AB$ is $1 \times 10^{-8}$ in a solution in which the concentration of $A^{+}$ ions is $10^{-3} \ M$. The salt will precipitate when the concentration of $B^{-}$ ions is kept

Concentration of $H_2SO_4$ and $Na_2SO_4$ in a solution is $1 \ M$ and $1.8 \times 10^{-2} \ M$,respectively. Molar solubility of $PbSO_4$ in the same solution is $X \times 10^{-Y} \ M$ (expressed in scientific notation). The value of $Y$ is. . . .
[Given: Solubility product of $PbSO_4$ $(K_{sp})=1.6 \times 10^{-8}$. For $H_2SO_4$,$K_{a1}$ is very large and $K_{a2}=1.2 \times 10^{-2}$]