Oxidation number of the nitrogen atom in HNO3 is : A. – 1 B. + 1 C. 0 D. + 4 E. + 5
The Correct Answer and Explanation is:
The correct answer is E. +5.
Explanation:
In order to determine the oxidation number of nitrogen in HNO3 (nitric acid), we need to follow the rules for assigning oxidation numbers:
- Hydrogen (H) typically has an oxidation number of +1 in most of its compounds (except when it’s in hydrides with metals).
- Oxygen (O) typically has an oxidation number of -2 in most of its compounds, except in peroxides or superoxides.
- The sum of the oxidation numbers of all atoms in a neutral molecule is zero.
Now let’s break down HNO3:
- Hydrogen (H) has an oxidation number of +1.
- Oxygen (O) has an oxidation number of -2. Since there are three oxygen atoms in HNO3, the total contribution from oxygen atoms is 3 × -2 = -6.
- Let the oxidation number of nitrogen (N) be xxx.
So, the sum of the oxidation numbers for the atoms in HNO3 should equal zero, as the compound is neutral:(+1)+(x)+3(−2)=0(+1) + (x) + 3(-2) = 0(+1)+(x)+3(−2)=0
Simplifying:1+x−6=01 + x – 6 = 01+x−6=0x−5=0x – 5 = 0x−5=0x=+5x = +5x=+5
Thus, the oxidation number of nitrogen in HNO3 is +5.
This makes sense because nitrogen is in a high oxidation state in nitric acid, which is a strong acid and an oxidizing agent. The +5 oxidation state corresponds to the nitrogen in its most common form in nitrates (NO3−) and other related compounds.
