Common Ion Effect in the Ionization of Acids and Bases

What is common ion effect? Write an example.

What is the correct relationship between the solubilities of $\mathrm{AgCl}$ in ${\mathrm{H}}_2\mathrm{O}, 0.01 \mathrm{M} {\mathrm{CaCl}}_2, 0.01 \mathrm{M} \mathrm{NaCl} \& 0.05 \mathrm{M} {\mathrm{AgNO}}_3$ if the values are ${\mathrm{S}}_1, {\mathrm{S}}_2, {\mathrm{S}}_3 \& {\mathrm{S}}_4$, respectively?

(Neglect any complexation)

An aqueous solution of ${\mathrm{H}}_2\mathrm{S}$ gas in water attains the following equilibrium.
${\mathrm{H}}_2{\mathrm{S}}_{\left(\mathrm{g}\right)}\rightleftharpoons {\mathrm{H}}_{\left(\mathrm{aq}\right)}^{+}+{\mathrm{HS}}_{\left(\mathrm{aq}\right)}^{-}$
If few $\mathrm{mL}$ of dilute $\mathrm{HCl}$ is added to the above solution, what will happen without change in temperature?

What is the molar solubility of $\mathrm{Ni}{\left(\mathrm{OH}\right)}_2$ in $1.0 \mathrm{M} \mathrm{NaOH}$?

(Given: Ionic product of $\mathrm{Ni}(\mathrm{OH}{)}_2=1.9\times {10}^{-15}$)

Arrange in increasing order of solubility of AgBr in solutions given here

(i) 0.1 M $\mathrm{N}{\mathrm{H}}_3$ (ii) 0.1 M $\mathrm{A}\mathrm{g}\mathrm{N}{\mathrm{O}}_3$ (iii) 0.2 M NaBr (iv) pure water

Which of the following activities will increase the $\left[{\mathrm{OH}}^{-}\right]$ of ${\mathrm{NH}}_4\mathrm{OH}$ solution?

The solubility product of $\text{Mg}{\left(\text{OH}\right)}_2$ is ${\text{10}}^{-14}$. The solubility of $\text{Mg}{\left(\text{OH}\right)}_2$ in buffer solution of pH = 8 is