explain the working of mercury cell
The half-reaction at the cathode is:
HgO + H2O + 2e- → Hg + 2OH -
The anode is made of zinc (Zn) and separated from the cathode with a layer of paper or other porous material soaked with electrolyte; this is known as a salt bridge. Two half-reactions occur at the anode. The first consists of an electrochemical reaction step:
Zn + 4OH- → Zn(OH)4-2 + 2e-followed by the chemical reaction step:
Zn(OH)4-2 → ZnO + 2OH- + H2Oyielding an overall anode half-reaction of:
Zn + 2OH- → ZnO + H2O + 2e-The overall reaction for the battery is:
Zn + HgO → ZnO + Hg