What is the solubility product $(K_{sp})$ of calcium phosphate in pure water? $[S = \text{molar solubility}]$

The compound insoluble in acetic acid is

Assign $A$,$B$,$C$,$D$ from the given type of reaction.
$CaSO_3 \downarrow + SO_2 + H_2O \longrightarrow Ca(HSO_3)_2$

The sulphide ion concentration $[S^{2-}]$ in a saturated $H_2S$ solution is $1 \times 10^{-22} \ M$. Which of the following sulphides should be quantitatively precipitated by $H_2S$ in the presence of dilute $HCl$?

Product	Sulphide Solubility $(K_{sp})$
$I$	$1.74 \times 10^{-16}$
$II$	$1.2 \times 10^{-22}$
$III$	$8.2 \times 10^{-46}$
$IV$	$5.0 \times 10^{-34}$

The solubility product of a salt having general formula $MX_2$ in water is $4 \times 10^{-12}$. The concentration of $M^{2+}$ ions in the aqueous solution of the salt is

$K_{sp}$ for $BaSO_4$ at $25 \, ^oC$ is $1.1 \times 10^{-10}$. To make the new solubility equal to $1.1 \times 10^{-8} \, M$,it is necessary to use a solution of $Na_2SO_4$ of the following concentration $....... \ M$