Q.

Given below are half-cell reactions:

MnO4-+8H++5e-⟶Mn2++4H2O ; EMn2+/MnO4-∘=-1.510 V

12O2+2H++2e-⟶H2O ; EO2/H2O∘=+1.223 V

Will the permanganate ion, MnO4- liberate O2 from water in the presence of an acid             [2022]

1 Yes, because Ecell∘=+0.287 V  
2 No, because Ecell∘=-0.287 V  
3 Yes, because Ecell∘=+2.733 V  
4 No, because Ecell∘=-2.733 V  

Ans.

(1)

Ecell∘=Ecathode∘-Eanode∘ =+1.510-1.223=+0.287 V

As Ecell∘ is positive, hence the reaction is feasible.