Given the standard electrode potentials. EFe2+/Fe∘=−0.44V and EH+/O2/H2O∘=1.23V
-0.79 V
-1.67 V
1.67 V
+0.79 V
Ecell∘=EH+/O2/H2O∘−EFe2+/Fc∘=1.23−(−0.44)=1.67V