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 carbides evolve saturated hydrocarbon gas upon hydrolysis, we will analyze each option step by step.

### Step 1: Understand what carbides are
Carbides are compounds composed of carbon and a less electronegative element. They can react with water to produce hydrocarbons.

### Step 2: Analyze each carbide option

**Option A: Calcium Carbide (CaC2)**
- Reaction with water:
\[ \text{CaC}_2 + 2 \text{H}_2\text{O} \rightarrow \text{Ca(OH)}_2 + \text{HC} \equiv \text{CH} \]
- Product: Acetylene (HC≡CH) is produced, which is an unsaturated hydrocarbon due to the triple bond.

**Conclusion for A**: Not a saturated hydrocarbon.

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**Option B: Aluminum Carbide (Al4C3)**
- Reaction with water:
\[ \text{Al}_4\text{C}_3 + 12 \text{H}_2\text{O} \rightarrow 4 \text{Al(OH)}_3 + 3 \text{CH}_4 \]
- Product: Methane (CH4) is produced, which is a saturated hydrocarbon (no double or triple bonds).

**Conclusion for B**: This is a saturated hydrocarbon.

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**Option C: Magnesium Carbide (Mg2C3)**
- Reaction with water:
\[ \text{Mg}_2\text{C}_3 + 6 \text{H}_2\text{O} \rightarrow 2 \text{Mg(OH)}_2 + 3 \text{HC} \equiv \text{CCH}_3 \]
- Product: Propine (HC≡CCH3) is produced, which is an unsaturated hydrocarbon due to the triple bond.

**Conclusion for C**: Not a saturated hydrocarbon.

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**Option D: Beryllium Carbide (Be2C)**
- Reaction with water:
\[ \text{Be}_2\text{C} + 4 \text{H}_2\text{O} \rightarrow 2 \text{Be(OH)}_2 + \text{CH}_4 \]
- Product: Methane (CH4) is produced, which is a saturated hydrocarbon.

**Conclusion for D**: This is a saturated hydrocarbon.

### Final Answer:
The carbides that evolve saturated hydrocarbon gas upon hydrolysis are:
- **B. Al4C3**
- **D. Be2C**