Sodium carbonate is prepared by Solvay process. Which of the following compounds is obtained as a by - product?

Options

A. `NH_(4)Cl`
B. `NH_(3)`
C. `CO_(2)`
D. `CaCl_(2)`

Answer

To determine the by-product obtained during the preparation of sodium carbonate via the Solvay process, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding the Solvay Process**: The Solvay process, also known as the ammonia-soda process, is a method for producing sodium carbonate (Na2CO3) from sodium chloride (NaCl), ammonia (NH3), and carbon dioxide (CO2).

2. **Initial Reaction**: The process begins with the reaction of ammonia, water, and carbon dioxide to form ammonium bicarbonate (NH4HCO3):
\[ NH3 + H2O + CO2 \rightarrow NH4HCO3 \]

3. **Formation of Sodium Bicarbonate**: Ammonium bicarbonate then reacts with sodium chloride to produce sodium bicarbonate (NaHCO3) and ammonium chloride (NH4Cl):
\[ NH4HCO3 + NaCl \rightarrow NaHCO3 + NH4Cl \]

4. **Thermal Decomposition**: Sodium bicarbonate is then subjected to thermal decomposition, which produces sodium carbonate, water, and carbon dioxide:
\[ 2 NaHCO3 \rightarrow Na2CO3 + H2O + CO2 \]

5. **Recycling of By-products**: The carbon dioxide produced can be reused in the process. Additionally, calcium carbonate (CaCO3) is often used to provide the necessary carbon dioxide, which decomposes to yield more CO2:
\[ CaCO3 \rightarrow CaO + CO2 \]

6. **Final By-product**: The reaction involving calcium hydroxide (produced from the decomposition of calcium carbonate) and ammonium chloride yields calcium chloride (CaCl2) as a by-product:
\[ Ca(OH)2 + 2 NH4Cl \rightarrow CaCl2 + 2 NH3 + 2 H2O \]

7. **Conclusion**: The by-product of the Solvay process is calcium chloride (CaCl2).

### Final Answer:
The compound obtained as a by-product in the Solvay process is **Calcium Chloride (CaCl2)**.

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