The following cell is used for measuring the partial pressure of oxygen at 700oC.
(Pt) Cu2Cu20 / 0.85 ZrO2 - 0.l5 CaO / O2 (Pt)
Knowing that conduction through the solid electrolyte (calcia stabilized zirconia) is attributed to the O-2 ions, derive the equation relating the cell e.m.f. to the partial pressure of oxygen. Use data from the Chemical Thermodynamic Properties.