(i) `SiO_(2) + NaOH to ?`
(ii) `SiO_(2) + HF to ? `
The products of (ii) & (i) respectively are

Options

A. `H_(2) SiF_(6) , SiO_(4)^(4-)`
B. `SiF_(4) , Na_(2) SiO_(3)`
C. `Na_(2) SiO_(3) , SiF_(4)`
D. `Na_(2) SiO_(4) , H_(2) SiF_(6)`

Answer

To solve the question, we need to analyze the reactions of silicon dioxide (SiO₂) with sodium hydroxide (NaOH) and hydrofluoric acid (HF) step by step.

### Step-by-Step Solution:

**(i) Reaction of SiO₂ with NaOH:**

1. **Identify Reactants:**
- Silicon Dioxide (SiO₂)
- Sodium Hydroxide (NaOH)

2. **Determine the Nature of the Reaction:**
- SiO₂ is a weak acid, and NaOH is a strong base. When they react, they form a silicate.

3. **Write the Balanced Chemical Equation:**
- The reaction can be represented as:
\[ \text{SiO}_2 + 2 \text{NaOH} \rightarrow \text{Na}_2\text{SiO}_3 + \text{H}_2\text{O} \]
- Here, sodium silicate (Na₂SiO₃) and water (H₂O) are produced.

4. **Identify the Product:**
- The product of this reaction is Sodium Silicate (Na₂SiO₃).

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**(ii) Reaction of SiO₂ with HF:**

1. **Identify Reactants:**
- Silicon Dioxide (SiO₂)
- Hydrofluoric Acid (HF)

2. **Determine the Nature of the Reaction:**
- HF is a strong acid, and it reacts with SiO₂ to form silicon tetrafluoride.

3. **Write the Balanced Chemical Equation:**
- The reaction can be represented as:
\[ \text{SiO}_2 + 4 \text{HF} \rightarrow \text{SiF}_4 + 2 \text{H}_2\text{O} \]
- Here, silicon tetrafluoride (SiF₄) and water (H₂O) are produced.

4. **Identify the Product:**
- The product of this reaction is Silicon Tetrafluoride (SiF₄).

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### Final Products:
- From (i): Sodium Silicate (Na₂SiO₃)
- From (ii): Silicon Tetrafluoride (SiF₄)

### Summary of Products:
- The products of the reactions are:
- (i) SiO₂ + NaOH → Na₂SiO₃
- (ii) SiO₂ + HF → SiF₄

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