Ncert Exercises & Solutions

Which of the carbonates given below is unstable in air and is kept in CO₂ atmosphere to avoid decomposition?

1. ${BeCO}_{3}$

2. ${MgCO}_{3}$

3. ${CaCO}_{3}$

4. ${BaCO}_{3}$

Hint: BeO is more stable than BeCO₃

{BeCO}_{3}

is unstable to the extent that it is stable only in an atmosphere of CO₂.

{BeCO}_{3}

shows reversible reaction because the stability of oxide formed is more than carbonates.

{BeCO}_{3} ⇌ BeO + {CO}_{2}

{BeCO}_{3}

is unstable due to the strong polarising effect of small Be²⁺ ion on the large polarizable carbonation. Moreover, extra

stability of the oxide is achieved through lattice energy by packing a small cation with a small oxide ion.