Which of the following liberates methane on treatment with water ?

Options

A. Silicon carbide
B. Calcium carbide
C. Beryllium carbide
D. Magnesium carbide

Answer

To determine which of the given compounds liberates methane when treated with water, we need to analyze each option.

### Step-by-Step Solution:

1. **Identify the Compounds:**
- The options provided are:
1. Silicon carbide (SiC)
2. Calcium carbide (CaC2)
3. Beryllium carbide (Be2C)
4. Magnesium carbide (Mg2C3)

2. **Reactions with Water:**
- **Silicon Carbide (SiC):**
- When silicon carbide is treated with water, it does not liberate methane. Instead, it forms silicon dioxide and other products.
- **Calcium Carbide (CaC2):**
- Calcium carbide reacts with water to produce acetylene (C2H2) and calcium hydroxide (Ca(OH)2). Acetylene can be further hydrogenated to form methane, but it does not directly liberate methane.
- **Beryllium Carbide (Be2C):**
- Beryllium carbide reacts with water to produce beryllium hydroxide and methane gas. This is a direct reaction that liberates methane.
- **Magnesium Carbide (Mg2C3):**
- Magnesium carbide reacts with water to produce magnesium hydroxide and acetylene, similar to calcium carbide. It does not directly liberate methane.

3. **Conclusion:**
- The only compound from the options that liberates methane directly upon treatment with water is **Beryllium Carbide (Be2C)**.

### Final Answer:
The compound that liberates methane on treatment with water is **Beryllium Carbide (Be2C)**.