Question

The brown ring complex \[[Fe{{({{H}_{2}}O)}_{5}}N{{O}^{+}}]S{{O}_{4}}\] has oxidation number of Fe as:
A. +1
B. +2
C. +3
D. +4

Answer 1

Hint:The oxidation number defined as the number of electrons which are gained or lose by the atom or ion. the oxidation number for the free element is always zero. For monoatomic ion the oxidation number is equal to the charge of ion. oxidation number is also known as oxidation state which is mainly used in coordination chemistry.

Complete answer:
So oxidation state or oxidation number is calculated by the number of electrons involved in bonding. There are atoms which form multiple bonds so all those bonds will be considered to be ionic and will be determined by the electrons involved in bonding.
So here let the oxidation number of Fe be ‘x’
The water molecule is a neutral molecule so its oxidation state will be zero.
The molecule NO has a positive charge here so its oxidation state will be considered as +1.
The molecule \[S{{O}_{4}}\] oxidation state will be -2.
So now forming the equation on the basis of above information,
\[x+5(0)+1-2=0\]
\[x+1-2=0\]
\[x=+1\]
So the oxidation number of Fe is =1.

Hence the correct answer for this question is option ‘a’.

Additional Information:
Oxidation number is used to determine the transfer of electrons. This is also used to determine the change that occurs in redox reactions. Larger the charge present on the ion or atom more difficult is to remove the electron.

Note:
The conditions for oxidation number is the following:
1. Bonds should be with heteroatoms.
2. They should always form ionic bonds either by gaining or losing the electrons, irrespective of seeing the actual nature of bonding.