The following compounds are heated (i) `KNO_(3)` (ii) `Cu(NO_(3))_(2)` (iii) `Pb(NO_(3))_(2)` (iv) `NH_(4)NO_(3)` . Which of the following statement/s is/are correct ?

Options

A. (ii) and (iii) liberate `NO_(2)`
B. (iv) liberates `N_(2)O`
C. (i), (ii) and (iii) liberate `O_(2)`
D. All statements are correct

Answer

To solve the question regarding the heating of the compounds \( KNO_3 \), \( Cu(NO_3)_2 \), \( Pb(NO_3)_2 \), and \( NH_4NO_3 \), we will analyze the decomposition reactions of each compound and determine which statements about the gases evolved are correct.

### Step-by-Step Solution:

1. **Heating of Potassium Nitrate (\( KNO_3 \))**:
- When \( KNO_3 \) is heated, it decomposes to form potassium nitrite (\( KNO_2 \)) and oxygen gas (\( O_2 \)).
- **Reaction**:
\[ 2 KNO_3 \rightarrow 2 KNO_2 + O_2 \]
- **Gas evolved**: Oxygen gas (\( O_2 \)).

2. **Heating of Copper(II) Nitrate (\( Cu(NO_3)_2 \))**:
- Upon heating, \( Cu(NO_3)_2 \) decomposes to produce copper(II) oxide (\( CuO \)), nitrogen dioxide (\( NO_2 \)), and oxygen gas (\( O_2 \)).
- **Reaction**:
\[ 2 Cu(NO_3)_2 \rightarrow 2 CuO + 4 NO_2 + O_2 \]
- **Gases evolved**: Nitrogen dioxide (\( NO_2 \)) and oxygen gas (\( O_2 \)).

3. **Heating of Lead(II) Nitrate (\( Pb(NO_3)_2 \))**:
- When heated, \( Pb(NO_3)_2 \) decomposes to form lead(II) oxide (\( PbO \)), nitrogen dioxide (\( NO_2 \)), and oxygen gas (\( O_2 \)).
- **Reaction**:
\[ 2 Pb(NO_3)_2 \rightarrow 2 PbO + 4 NO_2 + O_2 \]
- **Gases evolved**: Nitrogen dioxide (\( NO_2 \)) and oxygen gas (\( O_2 \)).

4. **Heating of Ammonium Nitrate (\( NH_4NO_3 \))**:
- Upon heating, \( NH_4NO_3 \) decomposes to produce nitrous oxide (\( N_2O \)) and water (\( H_2O \)).
- **Reaction**:
\[ 2 NH_4NO_3 \rightarrow N_2O + 2 H_2O + O_2 \]
- **Gas evolved**: Nitrous oxide (\( N_2O \)).

### Summary of Gases Evolved:
- \( KNO_3 \): Oxygen gas (\( O_2 \))
- \( Cu(NO_3)_2 \): Nitrogen dioxide (\( NO_2 \)) and oxygen gas (\( O_2 \))
- \( Pb(NO_3)_2 \): Nitrogen dioxide (\( NO_2 \)) and oxygen gas (\( O_2 \))
- \( NH_4NO_3 \): Nitrous oxide (\( N_2O \))

### Evaluating the Statements:
1. **Statement 1**: "Second and third liberate nitrogen dioxide gas."
- Correct (both \( Cu(NO_3)_2 \) and \( Pb(NO_3)_2 \) liberate \( NO_2 \)).

2. **Statement 2**: "Fourth liberates \( N_2O \) gas."
- Correct (ammonium nitrate liberates \( N_2O \)).

3. **Statement 3**: "First, second, and third liberate oxygen gas."
- Correct (all three compounds liberate \( O_2 \)).

### Conclusion:
All statements regarding the gases evolved from the heating of the given compounds are correct.

### Final Answer:
**All statements are correct.**

---