In the given chemical reaction, `2P+H_(2)O+CO_(2) to Q overset(H_(2)O+CO_(2))to 2R overset(NaCl)toS+NH_(4)Cl`
Identify S.

Options

A. `Na_(2)CO_(3)`
B. `NaOH`
C. `NaHCO_(3)`
D. `NH_(3)`

Explanation

To identify the substance S in the given chemical reaction, we can break down the process step by step.

### Step 1: Analyze the Given Reaction
The reaction provided is:
\[ 2P + H_2O + CO_2 \rightarrow Q \]
\[ H_2O + CO_2 \rightarrow 2R \]
\[ 2R + NaCl \rightarrow S + NH_4Cl \]

### Step 2: Identify the Components
From the context, it appears that the reaction involves the Solvay process, which is used to produce sodium carbonate (washing soda).

### Step 3: Determine the Role of Each Component
1. **2P**: In the context of the Solvay process, P is likely ammonia (NH₃), which is a key reactant.
2. **Q**: This could be ammonium carbonate (NH₄)₂CO₃, which is formed from ammonia, water, and carbon dioxide.
3. **R**: The reaction of ammonium carbonate with water and carbon dioxide likely yields ammonium bicarbonate (NH₄HCO₃).

### Step 4: Analyze the Final Reaction
The final reaction is:
\[ 2R + NaCl \rightarrow S + NH_4Cl \]
Substituting R with ammonium bicarbonate:
\[ 2(NH₄HCO₃) + NaCl \rightarrow S + NH₄Cl \]

### Step 5: Determine S
When ammonium bicarbonate reacts with sodium chloride (NaCl), it produces:
- Ammonium chloride (NH₄Cl)
- Sodium bicarbonate (NaHCO₃)

Thus, S is sodium bicarbonate (NaHCO₃).

### Conclusion
Therefore, the substance S identified in the reaction is:
\[ \text{S} = \text{NaHCO}_3 \text{ (sodium bicarbonate)} \]