Nitrogen gas is liberated by thermal decomposition of:

Options

A. `NH_(4)NO_(2)`
B. `NaN_(3)`
C. `(NH_(4))_(2)Cr_(2)O_(7)`
D. all

Explanation

To solve the question about which compounds liberate nitrogen gas upon thermal decomposition, we will analyze each option step by step.

### Step 1: Analyze Ammonium Nitrite
- **Chemical Formula**: NH4NO2
- **Thermal Decomposition Reaction**:
\[ 2 \, NH_4NO_2 \rightarrow 2 \, N_2 + 4 \, H_2O \]
- **Conclusion**: Ammonium nitrite decomposes to liberate nitrogen gas.

### Step 2: Analyze Sodium Azide
- **Chemical Formula**: NaN3
- **Thermal Decomposition Reaction**:
\[ 2 \, NaN_3 \rightarrow 2 \, Na + 3 \, N_2 \]
- **Conclusion**: Sodium azide decomposes to liberate nitrogen gas.

### Step 3: Analyze Ammonium Dichromate
- **Chemical Formula**: (NH4)2Cr2O7
- **Thermal Decomposition Reaction**:
\[ (NH_4)_2Cr_2O_7 \rightarrow Cr_2O_3 + 4 \, H_2O + N_2 \]
- **Conclusion**: Ammonium dichromate decomposes to liberate nitrogen gas.

### Step 4: Evaluate All Options
- **Option A**: Ammonium nitrite - Nitrogen gas is liberated.
- **Option B**: Sodium azide - Nitrogen gas is liberated.
- **Option C**: Ammonium dichromate - Nitrogen gas is liberated.
- **Option D**: All of the above - This is true since all the previous options liberate nitrogen gas.

### Final Answer
The correct answer is **Option D: All of them**.

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