The solubility product of $Mg(OH)_2$ is $9 \times 10^{-12}$. If the concentration of $Mg^{+2}$ is $0.01 \ M$,then the concentration of $OH^{-}$ is = .....

Sodium sulfate is soluble in water,whereas barium sulfate is sparingly soluble. Why?

An acidified solution of $0.05 \ M \ Zn^{2+}$ is saturated with $0.1 \ M \ H_2S$. What is the minimum molar concentration $(M)$ of $H^{+}$ required to prevent the precipitation of $ZnS$? Use $K_{sp}(ZnS) = 1.25 \times 10^{-22}$ and overall dissociation constant of $H_2S$,$K_{NET} = K_1 K_2 = 1 \times 10^{-21}$.

Observe the following solutions:
$(i)$ $1 \ L$ of $10^{-6} \ M \ AgNO_3$
$(ii)$ $1 \ L$ of $10^{-7} \ M \ AgNO_3$
$(iii)$ $1 \ L$ of $10^{-9} \ M \ AgNO_3$
$(iv)$ $1 \ L$ of $10^{-3} \ M \ AgNO_3$
$(v)$ $1 \ L$ of $10^{-5} \ M \ NaCl$
Which of the above two solutions when mixed will give a white precipitate,$AgCl$?
$(Given \ K_{sp} \ of \ AgCl = 1 \times 10^{-10})$

At $T(K)$ in a saturated solution of $MgCO_3$ and $Ag_2CO_3$, if the concentration of $Mg^{2+}$ ion is $3.2 \times 10^{-5} \ M$, then the concentration of $Ag^{+}$ ion in the solution will be [Given: $K_{sp}(MgCO_3) = 1.6 \times 10^{-6}$ and $K_{sp}(Ag_2CO_3) = 8.0 \times 10^{-12}$ at $T(K)$]

Solubility products of $CuI$ and $Ag_{2}CrO_{4}$ have almost the same value $(\sim 4 \times 10^{-12})$. The ratio of solubilities of the two salts $(CuI : Ag_{2}CrO_{4})$ is closest to $....$