In laboratory silicon can be prepared by the reaction

Options

A. Silica with magnesium
B. By heating carbon in electric furnace
C. By heating potassium fluosilicate with potassium
D. None of these

Answer

To determine how silicon can be prepared in the laboratory, we will analyze the given options step by step.

### Step 1: Analyze the first option - Silica with Magnesium
We start with the reaction of silica (SiO₂) with magnesium (Mg). The balanced chemical reaction is:
\[ \text{SiO}_2 + 2\text{Mg} \rightarrow \text{Si} + 2\text{MgO} \]

**Hint:** Check if the reactants can yield silicon and if the reaction can be balanced.

### Step 2: Analyze the second option - Heating Carbon in Electric Furnace
Next, we consider the option of heating carbon in an electric furnace. The reaction is not specified, but generally, heating carbon alone does not produce silicon. Instead, it may produce carbon monoxide or carbon dioxide, depending on the conditions.

**Hint:** Consider what products are formed when carbon is heated alone.

### Step 3: Analyze the third option - Heating Potassium Fluosilicate with Potassium
The third option involves heating potassium fluosilicate (K₂SiF₆) with potassium (K). This reaction is also unlikely to yield silicon directly. Instead, it typically results in the formation of other compounds rather than elemental silicon.

**Hint:** Investigate the expected products when potassium fluosilicate is heated with potassium.

### Step 4: Analyze the fourth option - None of These
The last option suggests that none of the methods listed are suitable for preparing silicon. However, since we have already established that the first option does indeed produce silicon, this option can be disregarded.

**Hint:** Reassess the previous options to confirm if any are valid methods for silicon preparation.

### Conclusion
Based on the analysis, the correct method for preparing silicon in the laboratory is:
**Silica with Magnesium** (Option A).

### Final Answer
The correct answer is **A: Silica with Magnesium**.