Question

The sum of oxidation number of nitrogen in \[N{{H}_{4}}N{{O}_{3}}\] is:
(a)+1
(b)+2
(c)+4
(d)none of these

Answer 1

Hint: Ammonium nitrite can ionise into two ions. Both contain one nitrogen atom. Each nitrogen atom has its individual oxidation state depending upon the total oxidation state.

Complete step-by-step answer:
Ammonium nitrate ionises as \[NH_{4}^{+}\] and \[NO_{3}^{-}\].
In ammonium, we know the oxidation state of hydrogen is always +1. There are 4 hydrogen in ammonium and the total oxidation state of ammonium is +1. Let us consider the oxidation state of nitrogen in ammonium nitrate as x.
X+4=+1
X=-3
The oxidation state of nitrogen in ammonium is -3.
In case of nitrate ion, oxygen has an oxidation state of -2. There are 3 oxygen atoms. So, the total oxidation state of oxygen in a nitrate molecule is -6. Total oxidation state of nitrate ion is -1. Therefore, oxidation state of nitrogen in nitrate ion is
X-6=-1
X=+5
Now let us calculate the sum of oxidation state of nitrogen in ammonium nitrate
Sum =5-3= +2
Sum of the two oxidation states of nitrogen in ammonium nitrate is +2.
The correct option is (b).

Additional Information: Oxidation states of an element represent the number of electrons that an atom is able to gain, lose, or share when it is chemically bonding with an atom of another element. It is also described as the transfer of electrons. Oxidation state is used to determine the changes in redox reactions and is similar to valence electrons, but is different from formal charge. The arrangement of atoms and the likelihood of the molecule existing is called a formal charge.

Note: Ammonium and ammonia are different. Ammonium is the ion of ammonia and is written as \[NH_{4}^{+}\]. Ammonia is a gas and ammonium is found in solution. Ammonium is basic in solution and gives a pH of 8.