Nitrogen forms largest number of oxides in which oxidation state of nitrogen varies from +1 to +5 `N_(2)O,NO,N_(2)O_(3),N_(2)O_(4) and N_(2)O_(5)` respectively. The largest number of oxides are formed due to capability of forming stable multiple bonds by nitrogen with oxygen.
Q. Which of the following oxides is known as anhydride of nitric acid?

Options

A. `N_(2)O_(5)`
B. `N_(2)O_(3)`
C. `NO`
D. All of these

Answer

To determine which oxide of nitrogen is known as the anhydride of nitric acid, we will analyze the given options step by step.

### Step 1: Understand the concept of anhydrides
An anhydride is a compound that can react with water to form an acid. In this case, we are looking for the oxide of nitrogen that, when reacted with water, produces nitric acid (HNO3).

**Hint:** Recall that anhydrides of acids are typically oxides that react with water to form the corresponding acid.

### Step 2: Analyze the options
The oxides of nitrogen provided are:
1. N2O5 (Nitrogen pentoxide)
2. N2O3 (Dinitrogen trioxide)
3. NO (Nitric oxide)
4. None of these

**Hint:** Focus on the chemical reactions of each oxide with water to see which one produces nitric acid.

### Step 3: Reaction of N2O5 with water
When nitrogen pentoxide (N2O5) reacts with water, it forms nitric acid (HNO3):
\[ \text{N}_2\text{O}_5 + \text{H}_2\text{O} \rightarrow 2 \text{HNO}_3 \]

**Hint:** This reaction is crucial because it directly shows that N2O5 produces nitric acid.

### Step 4: Reaction of N2O3 with water
When dinitrogen trioxide (N2O3) reacts with water, it forms nitrous acid (HNO2):
\[ \text{N}_2\text{O}_3 + \text{H}_2\text{O} \rightarrow \text{HNO}_2 \]

**Hint:** This indicates that N2O3 is not the anhydride of nitric acid, but rather of nitrous acid.

### Step 5: Reaction of NO with water
Nitric oxide (NO) does not react with water to form either nitric or nitrous acid. Therefore, it cannot be considered an anhydride of any acid.

**Hint:** Consider the nature of NO and its lack of reactivity with water in this context.

### Step 6: Conclusion
From the analysis above, we can conclude that:
- N2O5 is the oxide that is known as the anhydride of nitric acid because it produces HNO3 upon reaction with water.
- N2O3 is the anhydride of nitrous acid, and NO does not form any acid.

Thus, the correct answer is:
**N2O5 (Nitrogen pentoxide)** is the anhydride of nitric acid.

**Final Answer:** N2O5