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Zinc Carbon Cell

  1. May 29, 2005 #1
    The hydrogen liberated at the cathode would coat the electrode so polarises the cell. And manganse (IV) oxide is used as a depolariser. I got an equation in my notes:

    2MnO2 + 3H2 --> 2MHO(OH) + 2H2O.

    But evidently the oxygen doesn't balance.

    I tried looking on the internet but still no equation. Can someone help?
    (also the overall equation does not contain hydrogen at all, can someone explain that?)

  2. jcsd
  3. May 29, 2005 #2


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    Staff: Mentor

  4. May 29, 2005 #3
    I found this:

    Cathode: 2 NH4+ (aq) + 2 MnO2 (s) + 2e- --> Mn2O3 (s) + 2 NH3 (aq) + H2O (l)

    But hydrogen is not in the equation. I want to know exactly the reaction between manganese oxide and hydrogen gas.
  5. May 29, 2005 #4
    From my notes i got:

    2NH4+ + 2e- --> 2NH3 + H2

    However another source gives different equations:
    Cathode: 2 MnO2(s) + 2 NH4+(aq) + 2 e- ---> Mn2O3(s) + NH3(aq) + H2O

    2 MnO2(s) + 2 NH4+(aq) + Zn(s)  Mn2O3(s) + NH3(aq) + H2O + Zn2+(aq)

    so there nothing about hydrogen gas?
    Last edited: May 29, 2005
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