Q: 12. Discuss the various reactions that occur in the Solvay process.
Solvay process is used to prepare sodium carbonate.
When carbon dioxide gas is bubbled through a brine solution saturated with ammonia, sodium hydrogen carbonate is formed. This sodium hydrogen carbonate is then converted to sodium carbonate.
Step 1: Brine solution is saturated with ammonia.
This ammoniated brine is filtered to remove any impurity.
Step 2: Carbon dioxide is reacted with this ammoniated brine to result in the formation of insoluble sodium hydrogen carbonate.
Step 3: The solution containing crystals of is filtered to obtain.
Step 4: is heated strongly to convert it into.
Step 5: To recover ammonia, the filtrate (after removing ) is mixed with and heated
The overall reaction-taking place in Solvay process is
Q: 13. Potassium carbonate cannot be prepared by Solvay process. Why?
Solvay process cannot be used to prepare potassium carbonate. This is because unlike sodium bicarbonate, potassium bicarbonate is fairly soluble in water and does not precipitate out.
Q: 14. Why is decomposed at a lower temperature whereas at higher temperature?
As we move down the alkali metal group, the electropositive character increases. This causes an increase in the stability of alkali carbonates. However, lithium carbonate is not so stable to heat. This is because lithium carbonate is covalent. Lithium ion, being very small in size, polarizes a large carbonate ion, leading to the formation of more stable lithium oxide.
Therefore, lithium carbonate decomposes at a low temperature while a stable sodium carbonate decomposes at a high temperature.