Which of the following carbides reacts with `H_2O` to form propyne ?

Options

A. `Al_4C_3`
B. `CaC_2`
C. `SiC`
D. `Mg_2C_3`

Answer

To determine which carbide reacts with water to form propyne, we will analyze the given options step by step.

### Step 1: Identify the Carbides
We need to consider the following carbides:
1. Al4C3 (Aluminum carbide)
2. CaC2 (Calcium carbide)
3. SiC (Silicon carbide)
4. Mg2C3 (Magnesium carbide)

### Step 2: Reaction of Each Carbide with Water
We will analyze how each carbide reacts with water (H2O) and what products are formed.

#### 1. Aluminum Carbide (Al4C3)
When aluminum carbide reacts with water:
\[ \text{Al}_4\text{C}_3 + 12 \text{H}_2\text{O} \rightarrow 4 \text{Al(OH)}_3 + 3 \text{CH}_4 \]
- Products: Aluminum hydroxide and methane (CH4).

#### 2. Calcium Carbide (CaC2)
When calcium carbide reacts with water:
\[ \text{CaC}_2 + 2 \text{H}_2\text{O} \rightarrow \text{Ca(OH)}_2 + \text{C}_2\text{H}_2 \]
- Products: Calcium hydroxide and acetylene (C2H2).

#### 3. Silicon Carbide (SiC)
When silicon carbide reacts with water:
\[ \text{SiC} + 2 \text{H}_2\text{O} \rightarrow \text{SiO}_2 + \text{CH}_4 \]
- Products: Silicon dioxide and methane (CH4).

#### 4. Magnesium Carbide (Mg2C3)
When magnesium carbide reacts with water:
\[ \text{Mg}_2\text{C}_3 + 6 \text{H}_2\text{O} \rightarrow 2 \text{Mg(OH)}_2 + \text{C}_3\text{H}_4 \]
- Products: Magnesium hydroxide and propyne (C3H4).

### Step 3: Identify the Correct Product
Now we need to identify which of these reactions produces propyne (C3H4):
- From the analysis, only the reaction of magnesium carbide (Mg2C3) with water produces propyne.

### Conclusion
The carbide that reacts with water to form propyne is **Mg2C3 (Magnesium carbide)**.

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