Question

The oxidation state of $Fe$ in ${K_4}\left[ {Fe{{\left( {CN} \right)}_6}} \right]$ is:
A.$+ 2$
B.$+ 3$
C.$+ 4$
D.$+ 6$

Answer 1

:Hint: This question gives knowledge about oxidation number. Oxidation number is the charge present on an atom when it forms ionic bonds with different heteroatoms. Oxidation number is also termed as oxidation state.

Complete answer:
The oxidation state is not considered as the actual charge of an atom. Oxidation state plays a very crucial role in reduction and oxidation reactions. In oxidation reactions, the increase in oxidation state takes place whereas in reduction reactions, the decrease in oxidation state takes place. Oxidation reactions are also explained on the basis of loss of electrons or hydrogen whereas reduction reactions are explained on the basis of gain of electrons or hydrogen.
Let the oxidation state of iron be $x$.
Consider ${K_4}\left[ {Fe{{\left( {CN} \right)}_6}} \right]$ to determine the oxidation state of iron. In this molecule, the oxidation state of cyanide ion is $- 1$ and potassium is $+ 1$ . The overall charge on this compound is $0$. On summing up all the charges along with their molecularity we observe that the oxidation number of iron is $+ 2$.
Therefore, the oxidation state of iron in the complex ${K_4}\left[ {Fe{{\left( {CN} \right)}_6}} \right]$ is $+ 2$.

Hence, option $A$ is the correct option.

Note:
Always remember that the oxidation number is the charge present on an atom when it forms ionic bonds with different heteroatoms. Oxidation number is also termed as oxidation state. Electronegative elements generally have negative oxidation states.