Assertion: The carbonate of lithium decomposes easily on heating.
Reason: Lithium being very small in size polarises large carbonate ion leading to the formation of more stable `Li_(2)O and CO_(2)`.

Options

A. If both assertion and reason are true and reason is the correct explanation of assertion
B. If both assertion and reason are true but reason is not the correct explanation of assertion
C. If assertion is true but reason is false.
D. If both assertion and reason are false.

Answer

To solve the question regarding the decomposition of lithium carbonate (Li2CO3) upon heating, we will analyze both the assertion and the reason provided.

### Step-by-Step Solution:

1. **Understanding the Assertion**:
- The assertion states that lithium carbonate decomposes easily on heating.
- When heated, lithium carbonate decomposes to form lithium oxide (Li2O) and carbon dioxide (CO2).
- This reaction can be represented as:
\[ \text{Li}_2\text{CO}_3 \rightarrow \text{Li}_2\text{O} + \text{CO}_2 \]

2. **Understanding the Reason**:
- The reason given is that lithium, being very small in size, polarizes the large carbonate ion (CO3^2-).
- Polarization occurs when a small cation (like Li+) distorts the electron cloud of a larger anion (like CO3^2-), making the bond weaker and less stable.
- This leads to the formation of more stable products, Li2O and CO2, upon heating.

3. **Analyzing the Stability**:
- Lithium oxide (Li2O) is a more stable compound compared to lithium carbonate. This is due to the high lattice energy of Li2O, which arises from the small size of both lithium ions (Li+) and oxide ions (O^2-).
- The high lattice energy indicates strong ionic bonds, making Li2O more stable than Li2CO3.

4. **Conclusion**:
- Since both the assertion (that lithium carbonate decomposes easily) and the reason (that the small size of lithium leads to polarization of the carbonate ion) are true, and the reason correctly explains the assertion, we conclude that both statements are correct.

### Final Answer:
- Both the assertion and reason are true, and the reason correctly explains the assertion.