Question

ii) Explain common ion effect with an example. -​

Answer 1

The reduction of the degree of dissociation of a salt by the addition of a common-ion is called the common ion effect.
E.g.: In a saturated solution of silver chloride, we have the equilibrium:
AgCl
(aq)
​
⇌Ag
+
+Cl
−

When sodium chloride is added to the solution the concentration of Cl
−
ions will increases. The equilibrium shown above will be shifted to the left to form more of solid AgCl. Thus, the solubility of AgCl will decrease.

Answer 2

Explanation:

An example of the common ion effect can be observed when gaseous hydrogen chloride is passed through a sodium chloride solution, leading to the precipitation of the NaCl due to the excess of chloride ions in the solution (brought on by the dissociation of hc1