Which of the following is a sparingly soluble salt?

Assign $A, B, C, D$ from the given type of reaction.
$CaC_2O_4 \downarrow + CH_3COOH \longrightarrow$ No reaction

Solubility of $BaF_2$ in a solution of $Ba(NO_3)_2$ will be represented by the concentration term:

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

The solubility of a salt $M_2X_3$ is $y \ mol \ m^{-3}$. Its solubility product is:

$H_{2}S$ 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.$]$