Which of the following oxides of nitrogen is the anhydride of nitrous acid?

Options

A. `NO`
B. `N_(2)O_(3)`
C. `N_(2)O_(4)`
D. `N_(2)O_(3)`

Answer

To determine which oxide of nitrogen is the anhydride of nitrous acid, we can follow these steps:

### 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 anhydride that will form nitrous acid (HNO2) when it reacts with water.

**Hint:** Recall that anhydrides of acids are typically oxides of the elements that form those acids.

### Step 2: Identify the Relevant Nitrogen Oxides
The question provides several nitrogen oxides as options. We need to consider the common oxides of nitrogen, which include:
- N2O (Nitrous oxide)
- N2O3 (Dinitrogen trioxide)
- N2O4 (Dinitrogen tetroxide)
- N2O5 (Dinitrogen pentoxide)

**Hint:** Make a list of the nitrogen oxides provided in the options to analyze them one by one.

### Step 3: Determine the Reaction with Water
Next, we need to find out which of these oxides can react with water to produce nitrous acid (HNO2).

1. **N2O3 (Dinitrogen trioxide)**:
- N2O3 + H2O → 2 HNO2
- This reaction shows that N2O3 produces nitrous acid when it reacts with water.

2. **N2O5 (Dinitrogen pentoxide)**:
- N2O5 + H2O → 2 HNO3
- This reaction produces nitric acid (HNO3) instead of nitrous acid.

3. **N2O (Nitrous oxide)** and **N2O4 (Dinitrogen tetroxide)** do not produce nitrous acid when reacted with water.

**Hint:** Check the products of each reaction to see if they match the desired acid (HNO2).

### Step 4: Conclusion
From the analysis, we find that the oxide of nitrogen that is the anhydride of nitrous acid (HNO2) is **N2O3 (Dinitrogen trioxide)**.

**Final Answer:** The anhydride of nitrous acid is **N2O3**.