Assign oxidation numbers to each atom in nitrous acid. please explain
A) H = +1, N = +5, O = -1
B) H = +1, N = +5, O = -2
C) H = +1, N = +3, O = -1
D) H = +1, N = +3, O = 0
E) H = +1, N = +3, O = -2
The correct answer and explanation is :
The correct answer is:
E) H = +1, N = +3, O = -2
Explanation:
To determine the oxidation numbers of each atom in nitrous acid (HNO₂), we follow these steps:
Step 1: Assign known oxidation numbers
- Hydrogen (H) generally has an oxidation number of +1 when bonded to nonmetals.
- Oxygen (O) typically has an oxidation number of -2, except in peroxides or when bonded to fluorine.
- Nitrogen (N) will have an unknown oxidation number (x) in this case.
Step 2: Write the equation for the sum of oxidation numbers
Since the molecule HNO₂ is neutral (has no overall charge), the sum of oxidation numbers of all atoms must equal 0:
[
\text{Oxidation Number of H} + \text{Oxidation Number of N} + 2 \times \text{Oxidation Number of O} = 0
]
Substituting the known values:
[
(+1) + (x) + 2(-2) = 0
]
Step 3: Solve for x (oxidation number of nitrogen)
[
1 + x – 4 = 0
]
[
x – 3 = 0
]
[
x = +3
]
Thus, the oxidation numbers in HNO₂ are:
- H = +1
- N = +3
- O = -2
Why the other choices are incorrect?
- A and B: N is not +5 because that oxidation state corresponds to nitric acid (HNO₃), not nitrous acid.
- C: Oxygen is not -1 (this occurs in peroxides, such as H₂O₂).
- D: Oxygen cannot have an oxidation number of 0 in a compound.
Thus, the correct choice is E) H = +1, N = +3, O = -2.