The reaction which occur in the Galvanic cell is MnO4−+8H++5Fe2+⟶Mn2++5Fe3++4H2OE∘MnO4−,Mn2+,H+∣Pt=1.51V and E∘Fe3+,Fe2+∣Pt=0.77V(Q). The other concentrations are kept at unity except reducing Mn2+to 0.50 M, the emf of the cell is increased by
0.012 V
3.55×10−3V
0.059 V
0.018 V
ΔE=−0.0595log(0.5)=+3.55×10−3V