Question

\(\mathrm{Na}_{2} \mathrm{CO}_{3}\) can be manufactured by Solvay process but \(\mathrm{K}_{2} \mathrm{CO}_{3}\) cannot be prepared because (1) \(\mathrm{K}_{2} \mathrm{CO}_{3}\) is more soluble (2) \(\mathrm{K}_{2} \mathrm{CO}_{3}\) is less soluble (3) \(\mathrm{KHCO}_{3}\) is more soluble than \(\mathrm{NaHCO}_{3}\) (4) \(\mathrm{KHCO}_{3}\) is less soluble than \(\mathrm{NaHCO}_{3}\)

Short answer

Option (3) \(\mathrm{KHCO}_{3}\) is more soluble than \(\mathrm{NaHCO}_{3}\).

Step-by-step solution

Understand the Solvay Process

In the Solvay process, sodium carbonate (Na2CO3) is produced by reacting sodium chloride (NaCl) with ammonia (NH3) and carbon dioxide (CO2) in water. Sodium bicarbonate (NaHCO3) precipitates out and can be filtered and heated to produce Na2CO3.

Solubility of Bicarbonates

The solubility of the bicarbonates plays a crucial role in the Solvay process. Sodium bicarbonate (NaHCO3) is sparingly soluble, which allows it to precipitate out of the solution and be easily collected.

Compare Solubility of Potassium Bicarbonate

Potassium bicarbonate (KHCO3) is significantly more soluble in water compared to sodium bicarbonate (NaHCO3). This means that KHCO3 does not precipitate out as easily, making it unsuitable for the Solvay process.

Conclusion

Since KHCO3 is more soluble than NaHCO3, it cannot be easily precipitated and thus makes the Solvay process ineffective for producing K2CO3. Therefore, option (3) is the correct answer.

Key concepts

Sodium Carbonate Production

Sodium carbonate, commonly known as soda ash, is a crucial chemical in various applications like glass manufacturing, detergents, and water softening.
The primary industrial method to produce sodium carbonate is the Solvay process.
This process involves a series of chemical reactions starting with sodium chloride (NaCl), ammonia (NH3), and carbon dioxide (CO2).
The key steps are:

• Brine purification: Removes impurities from NaCl.
• Ammonia recovery: NH3 is reacted with CO2 and water.
• Formation of sodium bicarbonate: NaCl brine reacts with NH3 and CO2 to form NaHCO3, which precipitates out.
• Calcination: Heating NaHCO3 converts it to Na2CO3.

Efficient precipitation of sodium bicarbonate is crucial for the success of this process.

Solubility of Bicarbonates

Solubility describes how well a substance dissolves in a solvent, usually water.
In the Solvay process, the solubility of sodium bicarbonate (NaHCO3) is a critical factor.
NaHCO3 is sparingly soluble, meaning it does not dissolve well in water.
This low solubility allows NaHCO3 to precipitate out of the solution and be easily separated.
On the other hand, Potassium bicarbonate (KHCO3) is much more soluble.
This high solubility prevents KHCO3 from precipitating, making it unsuitable for the Solvay process.
This difference in solubility between NaHCO3 and KHCO3 is why sodium carbonate can be effectively produced using the Solvay process, while potassium carbonate cannot.

Chemical Manufacturing Processes

Chemical manufacturing processes involve transforming raw materials into valuable products.
The Solvay process is an excellent example of such a process.

• Initial raw materials (NaCl, NH3, CO2) are inexpensive and widely available.
• Recycling is a significant feature, like the recovery of ammonia.
• Each chemical reaction is carefully controlled to maximize yield and minimize waste.

Understanding the solubility of reactants and products, like in the case of bicarbonates, is fundamental to designing efficient manufacturing processes.
Similarly, reaction conditions such as temperature, pressure, and concentration play vital roles.
The overall goal is to optimize these parameters to achieve economic and environmental sustainability.