Question

Which of the following is least thermally stable?
(correct answer +1, wrong answer -0.25)

• A. $MgC{O}_3$
• B. $CaC{O}_3$
• C. $SrC{O}_3$
• D. $BaC{O}_3$

Answer 1

The correct option is A $MgC{O}_3$

Thermal stability of group 2 carbonates increases with the increase in size of the cation. As large size anion is stablised by large size cation.
Increasing order of cation size is: $Mg<Ca<Sr<Ba$
So, the most stable out of these carbonates is $BaC{O}_3$.