Assertion :The conversion of fresh precipitate to colloidal state is called peptization. Reason: It is caused by addition of common ions.
The conversion of freshly precipitated substance in to colloidal solution by shaking with the suitable electrolyte is called peptization, thus it is clear from definition that peptization is caused by addition of suitable electrolyte of specific ions, not by any common ions.
Thus both Assertion and Reason are correct but Reason is not the correct explanation for Assertion, Option B is correct.