Question

Which of the following compounds has the highest thermal stability?

• A. \( \text{Li}_2\text{CO}_3 \)
• B. \( \text{Na}_2\text{CO}_3 \)
• C. \( \text{K}_2\text{CO}_3 \)
• D. \( \text{Rb}_2\text{CO}_3 \)

Hint:

In general, smaller cations result in higher lattice energy, leading to greater thermal stability in ionic compounds like carbonates and nitrates.

Answer 1

The Correct Option is A

Thermal stability of metal carbonates generally increases as we move up the group of alkali metals. This is because the lattice energy (or bond strength) of the carbonate increases as the size of the cation decreases. Among the given options, \( \text{Li}_2\text{CO}_3 \) (Lithium carbonate) has the highest thermal stability due to the small size of the \( \text{Li}^+ \) ion, which results in a strong ionic bond and greater stability at higher temperatures. Thus, the correct answer is Option (A): \( \text{Li}_2\text{CO}_3 \).