Which of the following salts release reddish brown gas when heated in a dry test tube ?

Options

A. `LiNO_(3)`
B. `KNO_(3)`
C. `Pb(NO_(3))_(2)`
D. `AgNO_(3)`

Answer

To solve the question of which salts release reddish-brown gas when heated in a dry test tube, we can analyze each salt provided.

### Step-by-step Solution:

1. **Identify the Salts**: The salts mentioned are lithium nitrate (LiNO3), potassium nitrate (KNO3), lead(II) nitrate (Pb(NO3)2), and silver nitrate (AgNO3).

2. **Heating Lithium Nitrate (LiNO3)**:
- When lithium nitrate is heated, it decomposes into lithium oxide (Li2O), oxygen gas (O2), and nitrogen dioxide (NO2).
- **Observation**: Nitrogen dioxide is a reddish-brown gas.
- **Conclusion**: LiNO3 releases reddish-brown gas.

3. **Heating Potassium Nitrate (KNO3)**:
- Potassium nitrate decomposes upon heating to form potassium nitrite (KNO2) and oxygen gas (O2).
- **Observation**: No reddish-brown gas is produced.
- **Conclusion**: KNO3 does not release reddish-brown gas.

4. **Heating Lead(II) Nitrate (Pb(NO3)2)**:
- Lead(II) nitrate decomposes when heated to form lead oxide (PbO), oxygen gas (O2), and nitrogen dioxide (NO2).
- **Observation**: Nitrogen dioxide is produced, which is reddish-brown.
- **Conclusion**: Pb(NO3)2 releases reddish-brown gas.

5. **Heating Silver Nitrate (AgNO3)**:
- Silver nitrate decomposes upon heating to yield silver metal (Ag), oxygen gas (O2), and nitrogen dioxide (NO2).
- **Observation**: Nitrogen dioxide is produced, which is reddish-brown.
- **Conclusion**: AgNO3 releases reddish-brown gas.

6. **Final Conclusion**:
- The salts that release reddish-brown gas when heated are lithium nitrate (LiNO3), lead(II) nitrate (Pb(NO3)2), and silver nitrate (AgNO3).
- Therefore, the correct options are A (LiNO3), C (Pb(NO3)2), and D (AgNO3).