Saturated hydrocarbon gas is evolved by carbide(s) is/are

Options

A. `CaC_(2)`
B. `Al_(4)C_(3)`
C. `Mg_(2)C_(3)`
D. `Be_(2)C`

Answer

To determine which carbide(s) evolve saturated hydrocarbon gas upon hydrolysis, we will analyze the reactions of different carbides with water.

### Step-by-Step Solution:

1. **Understanding Carbides**:
- Carbides are compounds that contain carbon and a less electronegative element. They can react with water to produce various products, including hydrocarbons.

**Hint**: Remember that carbides can be classified based on their reactivity with water.

2. **Calcium Carbide Reaction**:
- When calcium carbide (CaC₂) reacts with water, it produces calcium hydroxide (Ca(OH)₂) and acetylene (C₂H₂) gas.
- Reaction:
\[ \text{CaC}_2 + 2 \text{H}_2\text{O} \rightarrow \text{Ca(OH)}_2 + \text{C}_2\text{H}_2 \]
- Acetylene is an unsaturated hydrocarbon because it contains a triple bond.

**Hint**: Identify the type of hydrocarbon produced (saturated vs unsaturated) based on the bonds present.

3. **Aluminium Carbide Reaction**:
- When aluminium carbide (Al₄C₃) reacts with water, it produces aluminium hydroxide (Al(OH)₃) and methane (CH₄) gas.
- Reaction:
\[ \text{Al}_4\text{C}_3 + 12 \text{H}_2\text{O} \rightarrow 4 \text{Al(OH)}_3 + 3 \text{CH}_4 \]
- Methane is a saturated hydrocarbon as it contains only single bonds.

**Hint**: Look for the products of the reaction and check if they are saturated hydrocarbons.

4. **Magnesium Carbide Reaction**:
- When magnesium carbide (Mg₂C₃) reacts with water, it forms magnesium hydroxide (Mg(OH)₂) and propane (C₃H₈) gas.
- Reaction:
\[ \text{Mg}_2\text{C}_3 + 6 \text{H}_2\text{O} \rightarrow 2 \text{Mg(OH)}_2 + \text{C}_3\text{H}_8 \]
- Propane is also an unsaturated hydrocarbon.

**Hint**: Again, check the type of hydrocarbon produced.

5. **Beryllium Carbide Reaction**:
- When beryllium carbide (Be₂C) reacts with water, it produces beryllium hydroxide (Be(OH)₂) and methane (CH₄) gas.
- Reaction:
\[ \text{Be}_2\text{C} + 4 \text{H}_2\text{O} \rightarrow 2 \text{Be(OH)}_2 + \text{CH}_4 \]
- Methane is a saturated hydrocarbon.

**Hint**: Compare the products of this reaction with those of aluminium carbide.

6. **Conclusion**:
- From the analysis:
- Calcium carbide produces acetylene (unsaturated).
- Aluminium carbide produces methane (saturated).
- Magnesium carbide produces propane (unsaturated).
- Beryllium carbide produces methane (saturated).
- Therefore, saturated hydrocarbon gases are evolved by **Aluminium Carbide** and **Beryllium Carbide**.

### Final Answer:
Saturated hydrocarbon gas is evolved by **Aluminium Carbide (B)** and **Beryllium Carbide (D)**.