Silicon dioxide is formed by the reaction of

Options

A. `SiCl_(4) + H_(2)O`
B. `SiO_(2) + HF`
C. `SiO_(2) + NaOH`
D. `SiCl_(4)+ NaOH`

Explanation

To determine how silicon dioxide (SiO2) is formed, we need to analyze the given options and identify the correct reaction.

### Step-by-Step Solution:

1. **Identify the Reactants**: The options provided are:
- A) SiCl4 + H2O
- B) SiO2 + HF
- C) SiO2 + NaOH
- D) SiCl4 + NaOH

2. **Analyze Each Option**:
- **Option A: SiCl4 + H2O**
- Silicon tetrachloride (SiCl4) reacts with water (H2O). This reaction is known to produce silicic acid (Si(OH)4) initially, which upon further heating can dehydrate to form silicon dioxide (SiO2).
- **Option B: SiO2 + HF**
- This reaction does not produce silicon dioxide; instead, HF reacts with SiO2 to form silicon tetrafluoride (SiF4).
- **Option C: SiO2 + NaOH**
- This reaction does not produce silicon dioxide; instead, it forms silicate salts.
- **Option D: SiCl4 + NaOH**
- This reaction can produce sodium silicate, but it does not directly yield silicon dioxide.

3. **Conclusion**: The correct reaction that leads to the formation of silicon dioxide is the reaction of silicon tetrachloride with water. Therefore, the answer is:
- **SiCl4 + H2O → SiO2 + HCl (upon heating)**

### Final Answer:
Silicon dioxide is formed by the reaction of **SiCl4 + H2O**.

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