What is the molar solubility of $Fe(OH)_2$ $(K_{sp} = 8.0 \times 10^{-16})$ at $pH$ $13.0$ ?

The best explanation for the solubility of $MnS$ in dil. $HCl$ is that

Solubility of $B(OH)_2$ in water at $25\,^{\circ}C$ is $10^{-7} \ M$. The value nearest to $K_{sp}$ is

Calculate solubility $(mol \ dm^{-3})$ of a sparingly soluble electrolyte $AB$ at $298 \ K$ if its solubility product is $1.6 \times 10^{-5}$?

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.

Assign $A$,$B$,$C$,$D$ from the given type of reaction.
$K_2[Cd(CN)_4] + H_2S \longrightarrow CdS \downarrow + 2KCN + 2HCN$