Question

Give reaction taking place at the two electrodes are made up to of ag.

Answer 1

  Ag/AgCl is a second type electrode in which the metal is in contact wit its low soluble salt and the anion of that salt.  In your case, the metal is Ag in contact with its low soluble salt AgCl + its anion Cl(-) and the reaction is  AgCl + e = Ag + Cl(-).  This reaction is the half cell of Ag/AgCl ref.electrode. Other reactions which are unwanted, are the complexes formed between AgCl and the high concentration of Cl(-) in satd. KCl. which are:  AgCl + Cl(-) = AgCl2(-) and further to AgCl3(2-).  These Complexes will cause the dissolution of AgCl and canceling its action as a reference El.  That is why few drops of Ag(+) ion is added to the El.half cell to form AgCl Saturated in the solution minimizing that effect.