Question

What is the difference in oxidation number of nitrogen when nitric acid is converted into nitrous oxide ?

• A. \(+1\)
• B. \(+2\)
• C. \(+4\)
• D. \(+3\)

Hint:

Find the oxidation number of nitrogen in each compound, then subtract.

Answer 1

The Correct Option is C

Step 1: Understanding the Concept:
Oxidation number of an element in a compound is found by assuming the sum of all oxidation numbers equals the net charge. Hydrogen is +1 and oxygen is -2.

Step 2: Nitrogen in nitric acid:
In \(\text{HNO}_3\): \(+1 + x + 3(-2) = 0\), so \(x = +5\).

Step 3: Nitrogen in nitrous oxide:
In \(\text{N}_2\text{O}\): \(2x + (-2) = 0\), so \(x = +1\).

Step 4: Detailed Explanation:
The change in oxidation number is \(+5 \to +1\), a decrease of \(5 - 1 = 4\). The magnitude of the difference is 4, meaning each nitrogen gains 4 electrons (it is reduced).

Step 5: Why the other options are wrong.
The value +1 (A) is the oxidation number of N in \(\text{N}_2\text{O}\) itself, not the difference. A difference of +2 (B) or +3 (D) would need a final oxidation number of +3 or +2, as in \(\text{N}_2\text{O}_3\) or NO, not \(\text{N}_2\text{O}\).

Final Answer:
The difference is \(4\), option (C). \[ \boxed{+4} \]