Question

Oxidation number of Fe in $Fe{C}_2{O}_4$ is?

Answer 1

Hint: In a neutral molecule, algebraic sum of oxidation number of all atoms in a compound must be zero. The oxidation number of oxygen is mostly -2. In this molecule, the oxidation number of carbon is +3.

Complete step by step answer:
Oxidation number is a number assigned to an element that represents the number of electrons lost or gained by an atom of that element of compound.
Following are some rules to determine oxidation number.
- In elements, each atom bears an oxidation number of zero in the free or uncombined state.
- Oxidation number of oxygen is mostly -2 but in peroxides and superoxide exceptions are there and when oxygen is bonded to fluorine it has an oxidation number like +1, +2.
- In a neutral molecule, the algebraic sum of the oxidation number of all atoms in a compound must be zero and in polyatomic ion, the algebraic sum of the oxidation number of atom of ion is equal to charge on the ion.

In a given molecule, let us consider the oxidation number of Fe as x.
As we know, the oxidation number of oxygen is -2 and as there are four oxygen atoms, the oxidation number of four oxygen atoms is -8.

-as we know carbon can have variable valency and $Fe{C}_2{O}_4$ has no charge so sum of oxidation number of all atoms must be zero, so sum of oxidation number of both carbon atoms is +6 so each carbon atom has oxidation number as +3.
$\Rightarrow$ x + 2(3) + 4 (-2) = 0
$\Rightarrow$ x + 6 - 8 = 0
$\Rightarrow$ x - 2 = 0
$\Rightarrow$ x = +2
The oxidation number of Fe in $Fe{C}_2{O}_4$ is +2.

Note: In all its compounds, fluorine has oxidation number as -1. In a neutral molecule, the algebraic sum of the oxidation number of all atoms in a compound must be zero.