Answer/ explanation :
The oxidation number of Fe
In Fe2O3
To solve this problem,
The oxidation number of O is -2
Oxidation number of Fe is x
Note that there are 2moles of Fe and 3moles of O
2 Fe + (-2 * 3) = 0
2 Fe + (-6) = 0
2 Fe - 6 = 0
2 Fe = 6
Fe = 6/2
Fe = +3
Therefore, the oxidation number of Fe is +3
The sign is very important, either - or +
