Which of the following compounds release reddish brown gas on heating?

Options

A. `N_(2)O_(4)`
B. `Ba(N_(3))_(2)`
C. `NH_(4)NO_(2)`
D. `KNO_(3)`

Answer

To determine which of the given compounds releases a reddish-brown gas upon heating, we will analyze each compound step by step.

### Step 1: Analyze the first compound, N2O4
- **Heating N2O4**: When dinitrogen tetroxide (N2O4) is heated, it decomposes into nitrogen dioxide (NO2).
- **Gas Released**: Nitrogen dioxide is known to be a reddish-brown gas.

**Conclusion for N2O4**: This compound releases a reddish-brown gas upon heating.

### Step 2: Analyze the second compound, Ba(N3)2
- **Heating Ba(N3)2**: When barium azide (Ba(N3)2) is heated, it decomposes into barium metal and nitrogen gas.
- **Gas Released**: Nitrogen gas (N2) is colorless.

**Conclusion for Ba(N3)2**: This compound does not release a reddish-brown gas; it releases a colorless gas.

### Step 3: Analyze the third compound, NH4NO2
- **Heating NH4NO2**: Ammonium nitrite (NH4NO2) decomposes upon heating to form water (H2O) and nitrogen gas.
- **Gas Released**: Nitrogen gas (N2) is colorless.

**Conclusion for NH4NO2**: This compound does not release a reddish-brown gas; it releases a colorless gas.

### Step 4: Analyze the fourth compound, KNO3
- **Heating KNO3**: Potassium nitrate (KNO3) decomposes upon heating to form potassium nitrite (KNO2) and oxygen gas.
- **Gas Released**: Oxygen gas (O2) is colorless.

**Conclusion for KNO3**: This compound does not release a reddish-brown gas; it releases a colorless gas.

### Final Conclusion
Among the given compounds, only N2O4 releases a reddish-brown gas (NO2) upon heating. Therefore, the correct answer is:

**Answer**: Option A: N2O4

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