Question

Which of the following compound has the highest thermal stability ?

• A. $NaCl$
• B. $CsCl$
• C. $KCl$
• D. $RbCl$

Answer 1

The correct option is A $NaCl$

The correct order of the lattice energies of alkali metal halides is $LiCl>NaCl>KCl>RbCl>CsCl$. This order is also valid for the thermal stabilities.
Hence, among the given alkali metal halides, $NaCl$ is highest thermal stability.