126. Balance the equation by oxidation number method:

(i) The skeleton equation along with O.N. of equation is 
     +3  -2      0               0     + 2     -2
     Fe₂O₃     + C        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    Fe + CO

(iv) On counting and balancing the atoms on both sides, we get the balanced equation. 

                   Fe₂O₃ + 3C  2Fe + 3CO