Balance the equation by oxidation number method:

$bold space bold Fe subscript bold 2 bold O subscript bold 3 bold space bold plus bold space bold C bold space bold space bold rightwards arrow bold space bold space bold space bold space bold Fe bold space bold plus bold space bold CO$

Solution

(i) The skeleton equation along with O.N. of equation is
+3 -2 0 0 + 2 -2
Fe₂O₃ + C $bold space bold rightwards arrow$ Fe + C O
Fe = +3 (C = 0) (Fe = 0) (C = +2)
Total O.N. Fe = 6
(ii) Noting the change in O.N. of above atoms,
Increase C = 0 to 2 i.e. 2
Decrease Fe = 3 to 0 i.e. 3
(iii) Equalise the increase/decrease in O.N. by multiplying C by 3
Fe₂O₃ + 3C $bold space bold rightwards arrow$ Fe + CO
(iv) On counting and balancing the atoms on both sides, we get the balanced equation.
Fe₂O₃ + 3C $space bold rightwards arrow$ 2Fe + 3CO