Question

Which of the carbonates given below is unstable in air and is kept in $CO_2$ atmosphere to avoid decomposition ?

• A. $BeCO_3$
• B. $MgCO_3$
• C. $CaCO_3$
• D. $BaCO_3$

Answer 1

Answer: (A)

$BeCO_3$

Answer 2

Beryllium carbonate is unstable due to the smaller size of cation and larger size of anion (as smaller cation stabilizes smaller anion through crystal lattice energy) and can be kept only in the atmosphere of $CO _{2}$. The thermal stability increases with increasing cationic size. Hence, $BeCO _{3}$ is unstable in air.