Which of the following pairs of ions would be expected to form a precipitate when their solutions are mixed?

Solubility of $Ca_{3}(PO_{4})_{2}$ is $S \ mol \ dm^{-3}$. Find the solubility product $(K_{sp})$.

The solubility product of $AgI$ at $25\,\text{°C}$ is $1.0 \times 10^{-16}\,\text{mol}^2\,\text{L}^{-2}$. The solubility of $AgI$ in $10^{-4}\,\text{N}$ solution of $KI$ at $25\,\text{°C}$ is approximately (in $\text{mol L}^{-1}$)

What is the minimum volume of water required to dissolve $1 \, g$ of calcium sulphate at $298 \, K$? (For calcium sulphate,$K_{sp}$ is $9.1 \times 10^{-6}$).

The solubility of $Ca(OH)_{2}$ is $s \ mol \ L^{-1}$. The solubility product $(K_{sp})$ under the same condition is:

The solubility of $PbI_2$ at $25\,^{\circ}C$ is $0.7\, g\, L^{-1}$. The solubility product of $PbI_2$ at this temperature is (molar mass of $PbI_2 = 461.2\, g\, mol^{-1}$)