Application of Common Ion Effect | Purification of NaCl

Common Ion Effect:

The process in which the ionization of weak electrolyte decreases (suppresses) by the addition of strong electrolyte is called Common Ion Effect.

Application of Common Ion Effect:

Purification of NaCl:
 NaCl    ⥨        Na+    +     Cl-        ( Weak Electrolyte)

 HCl        ⥨       H+      +    Cl-         ( Strong Electrolyte)

   We can use common ion effect for the purification of NaCl. For this purpose hot saturated solution of NaCl will be prepared,which establish the following equilibrium.

NaCl       ⥨     Na+    +     Cl-        ( Weak Electrolyte)

Now the HCl gas which is more ionizable is passed through this solution.It gives the following equilibrium.

 HCl       ⥨        H+      +    Cl-         ( Strong Electrolyte)
The concentration of the chloride ions (Cl-) will be considerably increased so the first equilibrium will be shift to the left.Solid NaCl will be settle down whereas impurities will be left behind.

Categories: chemistry

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