Solving Zinc Carbon Cell Equation: 2MnO2 + 3H2

[garytse86]

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.

 

[Borek]

Google leclanche cell reaction.

Chemical calculators at

 

[garytse86]

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.

 

[garytse86]

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?