Evaporation of $1 \ L$ of a saturated solution of $CaCO_3$ leaves a residue of $7.0 \ g$. What is the solubility product $(K_{sp})$ for $CaCO_3$?

$A$ solution is saturated with $SrCO_3$ and $SrF_2$. The $[CO_3^{2-}]$ is found to be $1.2 \times 10^{-3} \ M$. The concentration of $F^{-}$ in the solution would be:
Given: $K_{sp}(SrCO_3) = 7.0 \times 10^{-10}$, $K_{sp}(SrF_2) = 7.9 \times 10^{-10}$

Which of the following reagents can be used to separate $AgCl$ and $AgI$?

Solid $Ba(NO_3)_2$ is gradually dissolved in $1 \times 10^{-4} \ M \ Na_2CO_3$ solution. At what concentration of $Ba^{+2}$ will the precipitation of $BaCO_3$ start? (Given: $K_{sp}$ of $BaCO_3 = 5.1 \times 10^{-9}$)

Solid $Ba(NO_3)_2$ is gradually dissolved in a $1.0 \times 10^{-4} \ M$ $Na_2CO_3$ solution. At what concentration of $Ba^{2+}$ will a precipitate begin to form? ($K_{sp}$ for $BaCO_3 = 5.1 \times 10^{-9}$)

If the solubility product of $BaSO_4$ is $1.5 \times 10^{-9}$ in water,its solubility in moles per litre is