The precipitation occurs if the ionic product is

The solubility product of sparingly soluble salt $AX_{2}$ is $3.2 \times 10^{-11}$. Its solubility (in $mol / L$) is

$A$ solution which is $10^{-3} \ M$ each in $Mn^{2+}, Fe^{2+}, Zn^{2+},$ and $Hg^{2+}$ is treated with $10^{-16} \ M$ sulphide ion. If $K_{sp}$ of $MnS, FeS, ZnS,$ and $HgS$ are $10^{-15}, 10^{-23}, 10^{-20},$ and $10^{-54}$ respectively,which one will precipitate first?

$A$ precipitate is formed when:

$H_{2}S$ is passed into $1 \ L$ of a solution containing $0.1 \ mole$ of $Zn^{2+}$ and $0.01 \ mole$ of $Cu^{2+}$ until the sulphide ion concentration reaches $8.1 \times 10^{-19} \ M$. Which one of the following statements is true? $[K_{sp}$ of $ZnS$ and $CuS$ are $3 \times 10^{-22}$ and $8 \times 10^{-36}$ respectively.$]$

Solubility product of $CaC_2O_4$ at a given temperature in pure water is $4 \times 10^{-9} \ (mol \ L^{-1})^2$. Solubility of $CaC_2O_4$ at the same temperature is