`CO_(2)` gas along with solid `(Y)` is obtained when sodium salt `(X)` is heated. `(X)` is again obtained when `CO_(2)` has is passed into `(Y)`. `X` & `Y` are-

Options

A. `Na_(2)CO_(3), Na_(2)O`
B. `Na_(2)CO_(3), NaOH`
C. `NaHCO_(3),Na_(2)CO_(3)`
D. `Na_(2)CO_(3), NaHCO_(3)`

Explanation

To solve the problem, we need to identify the sodium salt (X) and the solid (Y) based on the given reactions involving CO₂ gas.

### Step-by-Step Solution:

1. **Identify the Sodium Salt (X)**:
- We are told that when sodium salt (X) is heated, it produces a solid (Y) and CO₂ gas.
- The possible candidates for sodium salts from the options are: Na₂CO₃, NaOH, NaHCO₃, and Na₂O.

2. **Heating Sodium Bicarbonate (NaHCO₃)**:
- When sodium bicarbonate (NaHCO₃) is heated, it decomposes to form sodium carbonate (Na₂CO₃), water (H₂O), and carbon dioxide (CO₂).
- The reaction can be written as:
\[ 2 \, \text{NaHCO}_3 \, \text{(s)} \rightarrow \text{Na}_2\text{CO}_3 \, \text{(s)} + \text{H}_2\text{O} \, \text{(g)} + \text{CO}_2 \, \text{(g)} \]
- Thus, when heated, NaHCO₃ produces Na₂CO₃ (solid Y) and CO₂ gas.

3. **Identify the Solid (Y)**:
- From the above reaction, we can conclude that solid (Y) is sodium carbonate (Na₂CO₃).

4. **Reversing the Reaction**:
- The question states that when CO₂ gas is passed into solid (Y), we obtain sodium salt (X) again.
- When CO₂ is bubbled through Na₂CO₃ (solid Y), it reacts with water to form sodium bicarbonate (NaHCO₃):
\[ \text{Na}_2\text{CO}_3 \, \text{(s)} + \text{CO}_2 \, \text{(g)} + \text{H}_2\text{O} \, \text{(l)} \rightarrow 2 \, \text{NaHCO}_3 \, \text{(s)} \]
- This confirms that when CO₂ is passed into Na₂CO₃, we regenerate NaHCO₃ (sodium bicarbonate), which is our sodium salt (X).

5. **Final Conclusion**:
- Therefore, we conclude that:
- Sodium salt (X) = NaHCO₃
- Solid (Y) = Na₂CO₃

### Final Answer:
- \( X = \text{NaHCO}_3 \) (sodium bicarbonate)
- \( Y = \text{Na}_2\text{CO}_3 \) (sodium carbonate)