The cell reaction is written as : E∘Co2+/Co3+=−1.81 V(SOP)∴E∘Co3+/Co2+=+1.81 V (SRP) EA//Al3+∘=+1.66 V(SOP)∴EAl3+/Al∘=−1.66 V(SRP) Here E∘ is given in standard Reduction Potential ∴Co3+/Co will undergo reduction acting as cathode and Al3+/Al will undergo oxidation acting as anode. ∴Ecell ∘Ecell ∘Ecell ∘=Ecathode (Red.) ∘−EAnode (oxide) ∘=1.81−(−1.66)=+3.47 V