Question

Question 10.14 Why is Li2CO3 decomposed at a lower temperature whereas Na2CO3 at higher temperature?

Class XI The s-Block Elements Page 305

Answer 1

Lithium being very small in size polarises a large CO3²- ion leading to the formation of more stable Li2O and CO2. All the carbonates of alkali metals (except lithium carbonate) are thermally quite stable.That's Why Li2CO3 is decomposed at a lower temperature whereas Na2CO3 at higher temperature.

Answer 2

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.

Li2CO3    LiO2 +  CO2

Therefore, lithium carbonate decomposes at a low temperature while a stable sodium carbonate decomposes at a high temperature.