Secondary Battery o The reaction in a secondary battery occurs many times. o Once it exhausts it can be recharged and used again. o
o
Mercury cell consists of zinc – mercury amalgam as the anode and a paste of HgO and carbon as the
Fig. Mercury cell o A paste of KOH and ZnO electrolyte used as an electrolyte.
o Theelectrode reactions for the cell are given below: Anode: Zn( Hg) + 2OH –-- > ZnO( s) + H2O + 2e – Cathode: HgO + H2O + 2e –-- > Hg( l) + 2OH – o
o
The overall reaction is represented by Zn( Hg) + HgO( s)-- > ZnO( s) + Hg( l)
The cell potential is approximately 1.35 V that remains constant throughout its lifetime.
Secondary Battery o The reaction in a secondary battery occurs many times. o Once it exhausts it can be recharged and used again. o
They are recharged by passing electric current through it in opposite direction.
o Example of secondary cell is lead and nickel cadmium cell.