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

The values of $K_{sp}$ of $CaCO_{3}$ and $CaC_{2}O_{4}$ are $4.7 \times 10^{-9}$ and $1.3 \times 10^{-9}$ respectively at $25 \, ^oC$. If the mixture of these two is washed with water,what is the concentration of $Ca^{2+}$ ions in water $\dots \times 10^{-5} \, M$?

According to the reaction $PbCl_2 \rightleftharpoons Pb^{2+} + 2Cl^-$,the solubility product constant $(K_{sp})$ of $PbCl_2$ is

If the solubility product of $AB_2$ is $3.20 \times 10^{-11} \ mol^3 L^{-3}$,then the solubility of $AB_2$ in pure water is......... $\times 10^{-4} \ mol \ L^{-1}$. [Assuming that neither kind of ion reacts with water]

If $K_{sp}$ is the solubility product of $Al(OH)_3$,its solubility is expressed by the formula:

For the following Assertion and Reason,the correct option is
Assertion $(A) :$ When $Cu^{2+}$ and sulphide ions are mixed,they react together extremely quickly to give a solid.
Reason $(R) :$ The equilibrium constant of $Cu^{2+}_{(aq)} + S^{2-}_{(aq)} \rightleftharpoons CuS_{(s)}$ is high because the solubility product is low.