On heating which of the following releases CO2 most easily?
- Na2CO3
- MgCO3
- CaCO3
- K2CO3
Answer
(2) MgCO3
Solution
As per NCERT, carbonates of alkali metals (except Li2CO3) are thermally stable and do not decompose easily.
⇒ Alkaline earth metal carbonates decompose on heating: MCO3 MO + CO2
⇒ Their thermal stability increases down the group, as the cation becomes larger and polarises the CO32- ion less: MgCO3 < CaCO3
∴ MgCO3 (small, highly polarising Mg2+) releases CO2 most easily.
Answer: (2)