In the manufacture of sodium carbonate, following reactions are involved:
`(A) overset(Delta)rarr (B) + CO_(2)`
`(B) +H_(2)O rarr (C ) overset(+NH_(4)Cl rarr (D)overset(+H_(2)O)rarr underset("Solution")(E )`
`(E )+CO_(2)rarr (F)`
`(F)+NaCl rarr (G) overset("Heat")rarr Na_(2)CO_(3)+CO_(2)+H_(2)O`
(D) is a gas which is soluble in `H_(2)O`
(A) is

Options

A. `Ca(HCO_(3))_(2)`
B. `CaCO_(3)`
C. `CaC_(2)`
D. `NaHCO_(3)`

Explanation

To solve the question regarding the manufacture of sodium carbonate and to identify compound (A), we can follow these steps:

### Step-by-Step Solution:

1. **Identify the Initial Reaction**:
The process of manufacturing sodium carbonate involves a series of chemical reactions. The first reaction given is:
\[ (A) \overset{\Delta}{\rightarrow} (B) + CO_2 \]
Here, we need to determine what (A) is.

2. **Recognize the Process**:
The manufacturing of sodium carbonate typically uses the Solvay process, which starts with the heating of calcium carbonate (CaCO3). When heated, calcium carbonate decomposes to form calcium oxide (CaO) and carbon dioxide (CO2):
\[ \text{CaCO}_3 \overset{\Delta}{\rightarrow} \text{CaO} + \text{CO}_2 \]
Thus, we can conclude that (A) is calcium carbonate (CaCO3).

3. **Identify (B)**:
From the reaction, we see that (B) is calcium oxide (CaO), which is produced when (A) is heated.

4. **Next Reaction**:
The next reaction involves (B) reacting with water:
\[ (B) + H_2O \rightarrow (C) \]
Calcium oxide reacts with water to form calcium hydroxide (Ca(OH)2):
\[ \text{CaO} + \text{H}_2O \rightarrow \text{Ca(OH)}_2 \]
Therefore, (C) is calcium hydroxide.

5. **Reaction with Ammonium Chloride**:
The next step involves (C) reacting with ammonium chloride (NH4Cl):
\[ (C) + NH_4Cl \rightarrow (D) \]
Calcium hydroxide reacts with ammonium chloride to produce ammonia (NH3) gas, which is (D), and calcium chloride (CaCl2):
\[ \text{Ca(OH)}_2 + 2\text{NH}_4\text{Cl} \rightarrow 2\text{NH}_3 + \text{CaCl}_2 + 2\text{H}_2O \]

6. **Formation of (E)**:
The ammonia gas (D) dissolves in water to form ammonium hydroxide (NH4OH), which is (E):
\[ \text{NH}_3 + \text{H}_2O \rightarrow \text{NH}_4\text{OH} \]

7. **Reaction with Carbon Dioxide**:
The next reaction involves (E) reacting with carbon dioxide:
\[ (E) + CO_2 \rightarrow (F) \]
Ammonium hydroxide reacts with carbon dioxide to form ammonium bicarbonate (NH4HCO3), which is (F).

8. **Final Reaction with Sodium Chloride**:
Finally, (F) reacts with sodium chloride (NaCl):
\[ (F) + NaCl \rightarrow (G) \]
This reaction produces sodium bicarbonate (NaHCO3), which is (G), along with ammonium chloride.

9. **Heating Sodium Bicarbonate**:
When sodium bicarbonate is heated, it decomposes to form sodium carbonate (Na2CO3), carbon dioxide, and water:
\[ 2\text{NaHCO}_3 \overset{\Delta}{\rightarrow} \text{Na}_2\text{CO}_3 + \text{CO}_2 + \text{H}_2\text{O} \]

### Conclusion:
From the above steps, we conclude that (A) is **calcium carbonate (CaCO3)**.