Which oxide of nitrogen condenses to a bluish liquid at `-30^@C`, but on warming it changes into reddish brown gas ?

Options

A. `N_2O_3`
B. `N_2O_5`
C. `N_2O_4`
D. `NO`

Answer

To solve the question, we need to identify the nitrogen oxide that condenses to a bluish liquid at -30°C and transforms into a reddish-brown gas upon warming.

### Step-by-Step Solution:

1. **Identify Nitrogen Oxides**:
- The common oxides of nitrogen include NO (Nitric oxide), NO2 (Nitrogen dioxide), N2O (Dinitrogen oxide), N2O3 (Dinitrogen trioxide), and N2O5 (Dinitrogen pentoxide).

2. **Check the Physical States of Each Oxide**:
- **NO**: Colorless gas at room temperature; does not condense to a bluish liquid.
- **NO2**: Reddish-brown gas at room temperature; does not condense to a bluish liquid.
- **N2O**: Colorless gas; does not condense to a bluish liquid.
- **N2O3**: This oxide is known to condense into a bluish liquid at -30°C.
- **N2O5**: Colorless solid at room temperature; does not condense to a bluish liquid.

3. **Behavior of N2O3**:
- When cooled below its condensation point, N2O3 forms a bluish liquid.
- Upon warming, N2O3 decomposes and releases NO2, which is a reddish-brown gas.

4. **Conclusion**:
- The oxide of nitrogen that meets the criteria of condensing to a bluish liquid at -30°C and transforming into a reddish-brown gas upon warming is **N2O3 (Dinitrogen trioxide)**.

### Final Answer:
The oxide of nitrogen that condenses to a bluish liquid at -30°C and changes into a reddish-brown gas upon warming is **N2O3 (Dinitrogen trioxide)**.

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