Question

Metal carbonates decompose on heating to give metal oxide and carbon dioxide. Which of the metal Carbonates is most stable thermally?
(a) $MgC{O}_3$ (b) $CaC{O}_3$ (c) $SrC{O}_3$ (d) $BaC{O}_3$

Answer 1

(d) $BaC{O}_3$ is thermally most stable because of the small size of resulting oxide ion. With the increase in atomic number, teh size of the metal ion, the stability fo the metal ion decreased and , hence that of carbonate increases (maximum in case of $BaC{O}_3)$ Therefore, the increasing size of cation destabilizes the oxides and hence does not favour the decomposition of heavier alkaline earth metal carbonates like BaCO_3\)