The solubility product of a soluble salt `A_(x)B_(y)` is given by : `K_(sp)=[A^(y+)]^(z)[B^(x-)]^(y)`. As soon as prodcut of concentration of `A^(y+)` and `B_(x-)`. Becomes more than its `K_(sp)`, the salt starts precipitation. It may practically be noticed that AgCI is more soluble in water and its solubility decreases dramatically in 0.1m NaCI or 0.1 m `AgNO_(3)` solution. It can be concluded that in presence of a common ion the solubility of salt decreases.
The pH of a saturated solution of Mg`(OH)_(2)` is :