Which of the following is a sparingly soluble salt?

The solubility of $CaF_2$ in a solution of $0.1 \ M \ Ca(NO_3)_2$ is.

Why is only $As^{3+}$ precipitated as $As_2S_3$ when $H_2S$ is passed through an acidic solution containing $As^{3+}$ and $Zn^{2+}$,while $Zn^{2+}$ is not precipitated as $ZnS$?

On the addition of a solution containing $CrO_4^{2-}$ ions to a solution containing $Ba^{2+}$,$Sr^{2+}$,and $Ca^{2+}$ ions,the precipitate obtained first will be of

$MX$ is a salt formed by neutralization of a strong base,$MOH$,and a weak acid,$HX$. If the dissociation constant of $HX$ is $K_a$ and the solubility product of $MX$ is $K_{sp}$,then the solubility of $MX$ in an aqueous acidic solution is given by:

What is the maximum concentration of equimolar solutions of ferrous sulphate and sodium sulphide so that when mixed in equal volumes,there is no precipitation of iron sulphide? (For iron sulphide,$K_{sp} = 6.3 \times 10^{-18}$).