Question

The precipitation occurs if the ionic concentration is
(A) Less than solubility product
(B) More than solubility product
(C) Equal to solubility product
(D) None of these

Answer 1

Hint: The solubility product of a sparingly soluble salt forming a saturated solution in water is calculated as the product of the concentrations of the ions, raised to a power equal to the number of the ions occurring in the equation representing the dissociation of the electrolyte. The solubility product is given by ${{K}_{sp}}$.

Complete Step by Step Solution:
When a solute is added to the solvent, it will get dissolved until the solution gets saturated. After that, the salt will not dissolve. This means that adding more solute will increase the ionic concentration more than the solubility product of the salt. Now, the undissolved salt will remain as a precipitate in the solution. The rate of precipitation will rise as the solution gets more concentrated, whereas the rate of dissolution will fall.
Correct Option: (B) More than solubility product.

Note: When the ionic product is equal to the solubility product, ions start forming. Precipitates start forming when an ionic product exceeds the solubility product. If we increase the concentration of any one of the ions, it should react with the ion of its opposite charge, and some salt will precipitate until the solubility product and ionic product are equal. Similar to this, if one of the ions' concentrations falls, more salt will dissolve in order to raise them both until the solubility product equals the ionic product once again.