LEAD ACID ACCUMULATORS

LEAD ACID ACCUMULATOR:

GASTON PLANTE

*IT IS ONE OF THE SECONDARY CELLS.

*ANODE - PbO2 ( LEAD OXIDE )
  CATHODE - SPONGY LEAD (Pb)
  ELECTROLYTE - Dil.H2SO4
  EMF - 2.2 V
  SPECIFIC GRAVITY OF THE ELECTROLYTE - 1.28

*THESE ARE PLACED IN A CONTAINER MADE UP OF HARD RUBBER OR GLASS OR CELLULOID.

*THE ELECTRODES ARE SEPARATED BY INSULATING MATERIALS AND ASSEMBLED TO GIVE LOW INTERNAL RESISTANCE SO THAT HIGH CURRENT IS DELIVERED.

WORKING

*AS THE CELL IS CONNECTED IN A CIRCUIT EXTERNALLY OXIDATION REACTION TAKES PLACE AT THE CATHODE.

*SPONGY LEAD REACTS WITH Dil.H2SO4 AND PRODUCES PbSO4 AND TWO ELECTRONS.
        Pb (SPONGY) + Dil.H2SO4 -----> PbSO4 + 2 electrons

*ELECTRONS FLOW FROM CATHODE TO ANODE EXTERNALLY ( REDUCTION REACTION TAKES PLACE AT THE ANODE )

*PbO2 REACTS WITH Dil.H2SO4 AND PRODUCES PbSO4 i.e.,
       PbO2 + Dil.H2SO4 ------> Pb(SO4)2 +2H2O

*TWO ELECTRONS  AND Pb IONS ARE NEUTRALISED IN THIS PROCESS.

*NOW THE CURRENT FLOW FROM ANODE TO CATHODE.

*AS THE CELL IS DISCHARGED BY DRAWING CURRENT FROM IT, THE EMF FALLS TO ABOUT 2 VOLTS.

*DURING CHARGING PROCESS CHEMICAL REACTIONS ARE REVERSED.


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