Topic: How to calculate the voltage of an alkaline battery? (Read 1939 times)

ForumUserGF · « **on:** May 17, 2018, 12:39:58 AM »

I just cannot get a voltage of 1.5V as the result. Here is what I have so far:

U = E0(cathode) – E0(anode)
 = 1,23 V - (-1,2 V)
 = 2,43 V

But this cannot be correct...

sjb · « **Reply #1 on:** May 17, 2018, 04:06:55 AM »

Well, the maths is right, but without seeing where this has come from, I'm not sure how to comment.

ForumUserGF · « **Reply #2 on:** May 17, 2018, 11:12:55 AM »

Well, the maths is right, but without seeing where this has come from, I'm not sure how to comment.

Well,

Oxydation: Zn + 4OH^-

[Zn(OH)₄]^2- + 2e^-Reduction: 2MnO₂ + H₂O + 2e^-

Mn₂O₃ + 2OH^-

And now you take E0(Mn²⁺/MnO₂) = 1,23V and E0(Zn/Zn(OH)₄^2-) = -1,199V. However, the result is wrong.

sjb · « **Reply #3 on:** May 17, 2018, 12:45:29 PM »

If the reduction is MnO₂

Mn₂O₃ why are you using E° for a different half reaction?