The standard cell potential (E o cell ) of the zinc-air battery is 1.65V. If at

Question

The standard cell potential (Eocell) of the zinc-air battery is 1.65V. If at 25.0oC the partial pressure of oxygen in the air diffusing its cathode is 0.24 atm, what is the cell potential (Ecell)? Assume the cell reaction is:

2 Zn(s) + O2(g) yields 2 ZnO(s)

The standard reduction potentials of the half-reactions in zinc-air batteries are:

ZnO(s) +H2O(l) + 2e- yields Zn(s) + 2OH-(aq) Eored = -1.25V

O2(g) + 2 H2O(l) + 4e- yields 4 OH-(aq) Eored= 0.401

Should use Nernst Equation and answer should be in volts. Thank you!

Explanation / Answer

nernest equation

Ecell = E0cell -0.0591/n*   x log [ZnO(s)]/[PO2]

Ecell = 1.65 -0.059 x1/4 x log [1]/[0.24]                 (here n=4 electrons transfered)

  Ecell     = 1.640 V

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