Hydrolysis of which of the following compound liberates acidic gas?

Options

A. `Li_(2)NH`
B. `Al_(2)S_(3)`
C. `CaC_(2)`
D. `CaNCN`

Explanation

To determine which compound liberates an acidic gas upon hydrolysis, we need to analyze the hydrolysis reactions of the given compounds one by one.

### Step-by-Step Solution:

1. **Identify the Compounds**: The compounds given are:
- Lithium imide (Li2H)
- Aluminum sulfide (Al2S3)
- Calcium carbide (CaC2)
- Calcium cyanamide (CaNCN)

2. **Define Hydrolysis**: Hydrolysis is a chemical reaction involving the breaking of a bond in a molecule using water. In this context, we are looking for the reaction of these compounds with water.

3. **Hydrolysis of Lithium Imide (Li2H)**:
- Reaction:
\[ \text{Li}_2\text{H} + \text{H}_2\text{O} \rightarrow \text{LiOH} + \text{NH}_3 \]
- Products: Lithium hydroxide (LiOH) and ammonia (NH3).
- Conclusion: Ammonia is a basic gas, not acidic.

4. **Hydrolysis of Aluminum Sulfide (Al2S3)**:
- Reaction:
\[ \text{Al}_2\text{S}_3 + 6\text{H}_2\text{O} \rightarrow 2\text{Al(OH)}_3 + 3\text{H}_2\text{S} \]
- Products: Aluminum hydroxide (Al(OH)3) and hydrogen sulfide (H2S).
- Conclusion: Hydrogen sulfide is an acidic gas.

5. **Hydrolysis of Calcium Carbide (CaC2)**:
- Reaction:
\[ \text{CaC}_2 + 2\text{H}_2\text{O} \rightarrow \text{Ca(OH)}_2 + \text{C}_2\text{H}_2 \]
- Products: Calcium hydroxide (Ca(OH)2) and acetylene (C2H2).
- Conclusion: Acetylene is weakly acidic, but not considered a strong acidic gas.

6. **Hydrolysis of Calcium Cyanamide (CaNCN)**:
- Reaction:
\[ \text{CaNCN} + 3\text{H}_2\text{O} \rightarrow \text{CaCO}_3 + \text{NH}_3 \]
- Products: Calcium carbonate (CaCO3) and ammonia (NH3).
- Conclusion: Ammonia is basic, not acidic.

7. **Final Conclusion**: The only compound that liberates an acidic gas upon hydrolysis is Aluminum sulfide (Al2S3), which produces hydrogen sulfide (H2S).

### Answer:
The compound that liberates an acidic gas upon hydrolysis is **Aluminum sulfide (Al2S3)**.