Which of the carbide will give methane when reacts with water-

Options

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

Answer

To determine which carbide will produce methane when reacted with water, we will analyze the reactions of different carbides with water step by step.

### Step 1: Identify the Carbides
The carbides we will consider are:
1. Beryllium carbide (BeC2)
2. Calcium carbide (CaC2)
3. Beryllium dicarbide (Be2C)
4. Magnesium carbide (Mg2C3)

### Step 2: Reaction of Beryllium Carbide (BeC2) with Water
When BeC2 reacts with water, the reaction is as follows:
\[ \text{BeC}_2 + 4 \text{H}_2\text{O} \rightarrow \text{Be(OH)}_2 + \text{CH}_4 + \text{CO} \]

**Products**: Beryllium hydroxide, methane (CH4), and carbon monoxide (CO).

### Step 3: Reaction of Calcium Carbide (CaC2) with Water
When CaC2 reacts with water, the reaction is:
\[ \text{CaC}_2 + 2 \text{H}_2\text{O} \rightarrow \text{Ca(OH)}_2 + \text{C}_2\text{H}_2 \]

**Products**: Calcium hydroxide and ethyne (C2H2), not methane.

### Step 4: Reaction of Beryllium Dicarbide (Be2C) with Water
When Be2C reacts with water, the reaction is:
\[ \text{Be}_2\text{C} + 4 \text{H}_2\text{O} \rightarrow 2 \text{Be(OH)}_2 + \text{CH}_4 \]

**Products**: Beryllium hydroxide and methane (CH4).

### Step 5: Reaction of Magnesium Carbide (Mg2C3) with Water
When Mg2C3 reacts with water, the reaction is:
\[ \text{Mg}_2\text{C}_3 + 6 \text{H}_2\text{O} \rightarrow 2 \text{Mg(OH)}_2 + \text{C}_3\text{H}_6 \]

**Products**: Magnesium hydroxide and propylene (C3H6), not methane.

### Conclusion
From the above reactions, we can conclude that:
- Beryllium carbide (BeC2) and Beryllium dicarbide (Be2C) produce methane when reacted with water.
- Calcium carbide (CaC2) and Magnesium carbide (Mg2C3) do not produce methane.

### Final Answer
The carbides that will give methane when reacted with water are:
- **Beryllium carbide (BeC2)**
- **Beryllium dicarbide (Be2C)**