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Q.Give construction and working of Dry cell.

Himachal HpboseHPBOSE Plus Two Board 2023Subjective· 2mImportance★★★★★
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The dry cell is a compact Leclanché-type primary cell: Zn container (anode), graphite rod (cathode) surrounded by MnO₂/carbon/NH₄Cl paste (electrolyte).

Construction:

  • The outer casing is a cylindrical zinc container, which itself acts as the anode.
  • In the centre is a graphite (carbon) rod, surrounded by a compact paste/powder of manganese dioxide (MnO2MnO_2) and carbon powder — this rod acts as the cathode.
  • The space between the zinc container and the central rod is filled with a moist paste of ammonium chloride (NH4ClNH_4Cl) and zinc chloride (ZnCl2ZnCl_2), which serves as the electrolyte.
  • The whole assembly is sealed at the top, with the carbon rod projecting out as the positive terminal and the zinc case as the negative terminal.

Working (electrode reactions):

At the anode (zinc container), oxidation occurs:

Zn(s)→Zn2++2e−Zn(s) \rightarrow Zn^{2+} + 2e^-

At the cathode, manganese dioxide is reduced (ammonium ions are also involved in the overall process):

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