Mn+7→Mn+2;Fe+2→Fe2+3Mn+7+5e−→Mn+2(1)×2;2Fe+2→Fe2+3+2e−(2)×52Mn+7+10e−→2Mn+2;10Fe2+2→5Fe2+3+10e−.
Therefore coefficient of KMnO4 is 2, that of MnSO4 is 2, that of FeSO4 is 10 and that of Fe2(SO4) is 5.
Therefore 2KMnO4+10FeSO4→2MnSO4+5Fe2(SO4)3
Coefficient of K2SO4 should be 1.
2KMnO4+10FeSO4→K2SO4+2MnSO4+5Fe2(SO4)3
To balance SO2−4 so that left hand side must have 8H2SO4, thus H2O also becomes 8H2O.
2KMnO4+10FeSO4+8H2SO4→K2SO4+2Mn(SO4)+5Fe2(SO4)3+8H2O