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The S-Block Elements

Question
CBSEENCH11007091
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Why is Li2CO3 decomposed at a lower temperature while Na2CO3 at higher temperature?

Solution
Li2CO3 is a salt of a weak base (LiOH) and a weak acid (CO2). Since weak base can not attract CO2 strongly, therefore Li2CO3 decomposes at a lower temperature. also, the strong polarising action of small Li+ ion distorts the electron cloud on the nearby oxygen atom of the large CO32- ion. Thus, the C-O bonds get weakened and Li-O bonds become stronger which ultimately leads to the decomposition of lithium carbonate to oxide and carbon dioxide.
Li subscript 2 CO subscript 3 space space rightwards arrow space space space Li subscript 2 straight O space plus space CO subscript 2
On the other hand, Na2CO3 is a salt of a strong base (NaOH) and a weak acid (H2CO3). Since NaOH is much stronger base than LiOH and hence can attract CO2 more strongly. Therefore Na2CO3 decomposes at much higher temperature because it is more stable than Li2CO3.

Some More Questions From The s-Block Elements Chapter

Why are alkali metals not found in nature?

Lithium shows similarities to magnesium in the chemical behaviour. What is the cause of this similarity?

What is the nature of lithium compounds?

Group 1 elements are called alkali metals. Why?

Why caesium can be used in photoelectric cell while lithium can not be?

In aqueous solution, Li+ ion has lowest mobility. Why?

Lithium has highest ionisation energy in group 1 elements, yet it is strongest reducing agent. Comment.

The softness of group 1 elements increases down the group with increasing atomic number. Give reason. 

Which is the most reactive alkali metal and why?

Why alkali metals do not form M2+ ions?

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