Solving Zinc Carbon Cell Equation: 2MnO2 + 3H2

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Discussion Overview

The discussion revolves around the chemical reactions involved in a zinc carbon cell, specifically focusing on the role of manganese dioxide (MnO2) and hydrogen gas (H2). Participants are exploring the equations related to the reactions at the cathode and the overall cell reaction, seeking clarification on the presence and balancing of hydrogen in these equations.

Discussion Character

  • Exploratory, Technical explanation, Debate/contested

Main Points Raised

  • One participant notes that hydrogen liberated at the cathode can coat the electrode, causing polarization, and mentions manganese (IV) oxide as a depolarizer. They provide an equation but express concern about the oxygen not balancing.
  • Another participant suggests looking up the Leclanché cell reaction for more information.
  • A different participant shares a cathode reaction involving ammonium ions and manganese oxide but points out that hydrogen is not included in the equation, seeking clarity on the reaction between manganese oxide and hydrogen gas.
  • Another participant presents their notes, which include a reaction involving ammonium ions and electrons, but also cites alternative equations that do not mention hydrogen gas, raising questions about its role in the overall reaction.

Areas of Agreement / Disagreement

Participants do not appear to reach a consensus on the equations or the role of hydrogen gas in the reactions. Multiple competing views and equations are presented, indicating ongoing uncertainty and debate.

Contextual Notes

There are limitations in the discussion regarding the balancing of oxygen in the proposed equations and the dependence on specific definitions of the reactions involved. The presence of hydrogen gas in the overall reaction remains unresolved.

garytse86
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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?)

Thanks.
 
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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.
 
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:

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