Calcium carbonate can be prepared by passing carbon dioxide through ….A.. Or by the addition of sodium carbonate to ….B…. Here, A and B refer to

Options

A. slaked lime, calcium chloride
B. calcium chloride, slaked lime
C. qulck lime, calcium chloride
D. calcium chloride, quick lime

Answer

To solve the question regarding the preparation of calcium carbonate (CaCO3) through two different methods, we need to identify what substances A and B refer to in the given reactions.

### Step-by-Step Solution:

1. **Understanding the Reactions**:
- The question states that calcium carbonate can be prepared by passing carbon dioxide (CO2) through a substance (A) or by adding sodium carbonate (Na2CO3) to another substance (B).

2. **Identifying Substance A**:
- The first method involves passing CO2 through a substance to produce CaCO3. A common reaction is:
\[ \text{Ca(OH)}_2 + \text{CO}_2 \rightarrow \text{CaCO}_3 + \text{H}_2\text{O} \]
- Here, Ca(OH)2 is known as **slaked lime** or **calcium hydroxide**. Therefore, we can conclude that:
\[ A = \text{Calcium hydroxide (Ca(OH)2)} \]

3. **Identifying Substance B**:
- The second method involves adding sodium carbonate to another substance. A common reaction is:
\[ \text{CaCl}_2 + \text{Na}_2\text{CO}_3 \rightarrow \text{CaCO}_3 + 2\text{NaCl} \]
- Here, CaCl2 is known as **calcium chloride**. Thus, we can conclude that:
\[ B = \text{Calcium chloride (CaCl2)} \]

4. **Final Conclusion**:
- From the above deductions, we can summarize that:
- A refers to **Calcium hydroxide (slaked lime)**.
- B refers to **Calcium chloride**.

### Answer:
A = Calcium hydroxide (slaked lime), B = Calcium chloride.