Question

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

Answer 1

Hint:Oxidation state is defined as the total number of electrons lost or gained in order to form a bond with another atom. It is a number which is assigned to every element of a compound. The sum of the net oxidation state of a neutral molecule is zero.

Complete answer:
We know that the oxidation state of a neutral compound is zero. We have been given the complex ${K_4}[Fe{(CN)_6}]$ where potassium is in cationic form and rest in anionic form. Here we have cyanide ion as a ligand whose charge is $ - 1$ and potassium is having $ + 2$ charge. We have to find the oxidation state of iron in this complex.
There is no charge on the complex and the complex is neutral.
Now we consider the charge on Fe is x
Considering all we get,
Oxidation number of potassium $ + x$ $ + $ $6 \times $ oxidation number of cyanide $ = $ charge on the complex
$ \Rightarrow 4 \times 1 + x + 6 \times - 1 = 0$
$ \Rightarrow 4 + x - 6 = 0$
$ \Rightarrow x - 2 = 0$
$ \Rightarrow x = 2$
Therefore the oxidation state of Fe in ${K_4}[Fe{(CN)_6}]$ is $ + 2$

Hence the correct answer is option A

Additional information:
Potassium ferrocyanide finds application in industries. It is used as an animal feed. It is also used as a fertiliser for plants. Prior to the early era it was the primary source for alkali metal cyanides. It was made by decomposition of potassium ferrocyanide.

Note:
${K_4}[Fe{(CN)_6}]$ is also known by the name potassium ferrocyanide. Upon treatment with chlorine gas, potassium ferrocyanide gets converted to potassium ferricyanide. This is used to remove potassium ferrocyanide from a solution. It is industrially prepared from hydrogen cyanide ferrous chloride and calcium hydroxide.