The number of mixed anhydride among the following are `N_2O_3` , `NO` , `N_2O_5` , `NO_2` , `N_2O`

Answer

To determine the number of mixed anhydrides among the given compounds \(N_2O_3\), \(NO\), \(N_2O_5\), \(NO_2\), and \(N_2O\), we will analyze each compound to see if it reacts with water to produce a mixture of two acidic anhydrides.

### Step-by-Step Solution:

1. **Identify Mixed Anhydride Definition**:
A mixed anhydride is a compound that reacts with water to produce a mixture of two different acidic anhydrides.

2. **Analyze \(N_2O_3\)**:
- Reaction: \(N_2O_3 + H_2O \rightarrow HNO_3 + N_2O\)
- Products: This reaction produces nitric acid \(HNO_3\) and nitrous oxide \(N_2O\).
- Conclusion: Only one acidic anhydride (HNO3) is formed. Hence, \(N_2O_3\) is **not** a mixed anhydride.

3. **Analyze \(NO\)**:
- Reaction: \(NO + H_2O\) does not react.
- Conclusion: Since there is no reaction, \(NO\) is **not** a mixed anhydride.

4. **Analyze \(N_2O_5\)**:
- Reaction: \(N_2O_5 + H_2O \rightarrow 2 HNO_3\)
- Products: This reaction produces only nitric acid \(HNO_3\).
- Conclusion: Only one acidic anhydride is formed. Hence, \(N_2O_5\) is **not** a mixed anhydride.

5. **Analyze \(NO_2\)**:
- Reaction: \(NO_2 + H_2O \rightarrow HNO_3 + HNO_2\)
- Products: This reaction produces both nitric acid \(HNO_3\) and nitrous acid \(HNO_2\).
- Conclusion: Two different acidic anhydrides are formed. Hence, \(NO_2\) **is** a mixed anhydride.

6. **Analyze \(N_2O\)**:
- Reaction: \(N_2O + H_2O\) does not react.
- Conclusion: Since there is no reaction, \(N_2O\) is **not** a mixed anhydride.

### Final Conclusion:
Among the compounds listed, the only mixed anhydride is \(NO_2\). Therefore, the number of mixed anhydrides among the given compounds is **1**.

### Summary:
- Mixed anhydrides identified: **1** (which is \(NO_2\)).