Question

What are the products formed when \(\text{Li}_2\text{CO}_3\) undergoes decomposition?

• A. \(\text{Li}_2\text{O} + \text{CO}_2\)
• B. \(\text{LiO} + \text{CO}_2\)
• C. \(\text{LiC} + \text{CO}_2\)
• D. \(\text{Li}_2\text{O}_2 + \text{CO}\)

Hint:

Among alkali metals, only lithium carbonate decomposes easily on heating due to high polarizing power.

Answer 1

The Correct Option is A

Step 1: Understanding the Concept:
Most group 1 metal carbonates are thermally stable. However, lithium carbonate (\(\text{Li}_2\text{CO}_3\)) is exceptional because of the small size of the \(\text{Li}^+\) ion, which polarizes the large carbonate (\(\text{CO}_3^{2-}\)) ion, leading to its decomposition upon heating.
Step 2: Key Formula or Approach:
Thermal decomposition of alkali metal carbonates generally follows the reaction: \[ \text{M}_2\text{CO}_3 \xrightarrow{\Delta} \text{M}_2\text{O} + \text{CO}_2 \] Step 3: Detailed Explanation:
Lithium belongs to group 1, and its carbonate is less stable compared to those of sodium or potassium. When \(\text{Li}_2\text{CO}_3\) is heated, it breaks down into lithium oxide and carbon dioxide gas.
Reaction: \[ \text{Li}_2\text{CO}_3(\text{s}) \xrightarrow{\Delta} \text{Li}_2\text{O}(\text{s}) + \text{CO}_2(\text{g}) \] Other alkali metal carbonates do not decompose at ordinary heating temperatures because the large cations stabilize the large carbonate anion.
Step 4: Final Answer:
The products are lithium oxide and carbon dioxide.