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 .