Metal carbides on reaction with `H_2O` form `CH_4` , Carbide can be

Options

A. `CaC_2`
B. `Mg_3C_2`
C. `Be_2C`
D. All of these

Answer

To solve the problem, we need to identify which metal carbide reacts with water (H₂O) to produce methane (CH₄).

### Step-by-Step Solution:

1. **Understanding Metal Carbides**:
Metal carbides are compounds formed between metals and carbon. When they react with water, they can produce various products, including hydrocarbons like methane (CH₄).

2. **Analyzing the Given Options**:
We need to evaluate each given carbide option to see if it produces CH₄ when reacted with water.

3. **Testing 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: This reaction produces calcium hydroxide (Ca(OH)₂) and acetylene (C₂H₂), not methane (CH₄).
- Conclusion: CaC₂ does not produce CH₄.

4. **Testing Magnesium Carbide (Mg₃C₂)**:
- Reaction: \( \text{Mg}_3\text{C}_2 + 6 \text{H}_2\text{O} \rightarrow 3 \text{Mg(OH)}_2 + \text{C}_2\text{H}_6 \)
- Products: This reaction produces magnesium hydroxide (Mg(OH)₂) and ethane (C₂H₆), not methane (CH₄).
- Conclusion: Mg₃C₂ does not produce CH₄.

5. **Testing Beryllium Carbide (Be₂C)**:
- Reaction: \( \text{Be}_2\text{C} + 4 \text{H}_2\text{O} \rightarrow 2 \text{Be(OH)}_2 + \text{CH}_4 \)
- Products: This reaction produces beryllium hydroxide (Be(OH)₂) and methane (CH₄).
- Conclusion: Be₂C does produce CH₄.

6. **Final Conclusion**:
After testing the metal carbides, we find that the only carbide that produces methane (CH₄) when reacted with water is **Beryllium Carbide (Be₂C)**.

### Answer:
The carbide that forms CH₄ on reaction with H₂O is **Be₂C**.