`CO_2` turns lime water milky, due to the formation of

Options

A. `Ca(HCO_3)_2`
B. `CaCO_3`
C. `Ca(OH)_2`
D. `CaO`

Explanation

To solve the question "CO₂ turns lime water milky, due to the formation of...", we can follow these steps:

### Step-by-Step Solution:

1. **Understanding Lime Water**:
- Lime water is an aqueous solution of calcium hydroxide (Ca(OH)₂). It is commonly used in various chemical tests.

2. **Reaction of CO₂ with Lime Water**:
- When carbon dioxide (CO₂) is bubbled through lime water, it reacts with calcium hydroxide.

3. **Chemical Reaction**:
- The reaction can be represented as:
\[ \text{Ca(OH)}_2 (aq) + \text{CO}_2 (g) \rightarrow \text{CaCO}_3 (s) + \text{H}_2\text{O} (l) \]
- In this reaction, calcium hydroxide reacts with carbon dioxide to form calcium carbonate (CaCO₃) and water (H₂O).

4. **Formation of Calcium Carbonate**:
- Calcium carbonate (CaCO₃) is a white precipitate that is insoluble in water. This precipitate is responsible for the milky appearance of the lime water.

5. **Conclusion**:
- Therefore, the reason CO₂ turns lime water milky is due to the formation of calcium carbonate (CaCO₃).

### Final Answer:
CO₂ turns lime water milky due to the formation of calcium carbonate (CaCO₃).

---