Question

Correct formula of potassium ferrocyanide is?
A.${K_4}{\left[ {Fe{{\left( {CN} \right)}_5}} \right]^ + }$
B.${K_3}\left[ {Fe{{\left( {CN} \right)}_6}} \right]{H_2}O$
C.${K_4}\left[ {Fe{{\left( {CN} \right)}_6}} \right]$
D.None of these

Answer 1

We have to remember that the molecular formula specifies the numbers of atoms present in the molecule of a chemical substance. And the molecular formula is the same as that of the empirical formula. The molecular formula mainly contains the chemical symbols of the corresponding element and it has numeric subscripts to express the number of atoms present in a molecule. Therefore, the molecular formula will show the actual number of atoms present in a molecule.

Complete answer:
The molecular formula of potassium ferricyanide is not equal to ${K_4}{\left[ {Fe{{\left( {CN} \right)}_5}} \right]^ + }$. Hence, option (A) is incorrect.
The molecular formula of potassium ferricyanide is not equal to ${K_3}\left[ {Fe{{\left( {CN} \right)}_6}} \right]{H_2}O$. Hence, option (B) is incorrect.
The molecular formula of potassium ferricyanide is ${K_4}\left[ {Fe{{\left( {CN} \right)}_6}} \right]$. In ferrocyanide, the oxidation number of iron is equal to $+ 2$
Let oxidation number of iron is equal to x. Then,
$\left[ {Fe{{\left( {CN} \right)}_6}} \right] = x + 6\left( { - 1} \right) = - 4$
By simplification, will get the value of x is equal to $+ 2$
Therefore the value of x is equal to $+ 2$. Thus, The molecular formula of potassium ferricyanide is ${K_4}\left[ {Fe{{\left( {CN} \right)}_6}} \right]$. Hence, option (C) is correct.
The molecular formula of potassium ferricyanide is ${K_4}\left[ {Fe{{\left( {CN} \right)}_6}} \right]$. Hence, option (D) is incorrect.

Hence, option (C) is correct.

Note:
As we know, the formula of potassium ferrocyanide is ${K_4}\left[ {Fe{{\left( {CN} \right)}_6}} \right]$. Potassium is a chemical element having the symbol $'K'$ with atomic number $19$. The components present in the compound are potassium, iron, carbon and nitrogen. Potassium ferrocyanide is a chemical compound with molar mass $368.34g/mol$. Potassium ferrocyanide is mainly used for the preparation of wine and citric acid. And it is also used to determine the concentration of potassium permanganate.