Name the cell used in hearing aids. Write the cell reaction. Why do they give consistent supply of current at a low potential?

Dear student,

The cell used in hearing aids is Mercury cell . In this cell anode is Zn- Hg amalgam and cathode is the paste of HgO and C .
The cell reactions are : 
   At anode :   Zn (amalgam)  +  2 OH-     ZnO (s)  + H2O   + 2e-
   At cathode :  HgO(s)  + H2O + 2e-     Hg(l)  + 2OH-
Over all reaction :  Zn   +  HgO     ZnO   +  Hg
Since the over all reaction does not involve any ion in solution whose concentration can change, the cell showes a consistance supply of current .


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