Question

The correct order of increasing thermal stability of $K_{2}C{O}_3,MgC{O}_{3}CaC{O}_3$ and $BeC{O}_3$ is:

• A. $BeC{O}_3<MgC{O}_3<CaC{O}_3<K_{2}C{O}_3$
• B. $MgC{O}_3<BeC{O}_3<CaC{O}_3<K_{2}C{O}_3$
• C. $K_{2}C{O}_3<MgC{O}_3<CaC{O}_3<BeC{O}_3$
• D. $BeC{O}_3<MgC{O}_3<K_{2}C{O}_3<.CaC{O}_3$

Answer 1

The correct option is A $BeC{O}_3<MgC{O}_3<CaC{O}_3<K_{2}C{O}_3$

• In all cases, for a particular set of e.g. Group 1 or Group 2 compounds, the thermal stability increases down the group as the ionic radius of the cation increases, and its polarising power decreases.
• Group 1 compounds tend to be more thermally stable than group 2 compounds because the cation has a smaller charge and a larger ionic radius, and so a lower polarising power. particularly when adjacent metals on the same period are compared.

Hence, the order of increasing thermal stability is $BeC{O}_3<MgC{O}_3<CaC{O}_3<K_{2}C{O}_3$