Question

The correct sequence of thermal stability of the following carbonates is:

• A. ${\mathrm{BaCO}}_3<{\mathrm{CaCO}}_3<{\mathrm{SrCO}}_3<{\mathrm{MgCO}}_3$
• B. ${\mathrm{MgCO}}_3<{\mathrm{CaCO}}_3<{\mathrm{SrCO}}_3<{\mathrm{BaCO}}_3$
• C. ${\mathrm{BaCO}}_3<{\mathrm{SrCO}}_3<{\mathrm{CaCO}}_3<{\mathrm{MgCO}}_3$
• D. ${\mathrm{MgCO}}_3<{\mathrm{SrCO}}_3<{\mathrm{CaCO}}_3<{\mathrm{BaCO}}_3$

Answer 1

The correct option is B

${\mathrm{MgCO}}_3<{\mathrm{CaCO}}_3<{\mathrm{SrCO}}_3<{\mathrm{BaCO}}_3$

Thermal stability:

• Thermal stability is defined as the ability of a fluid to resist breaking down under heat stress.
• The thermal stability of carbonates rises as one moves down the alkaline earth metal group.
• All of the carbonates in this category decompose thermally to metal oxide and carbon dioxide gas (${\mathrm{CO}}_2$).
• The carbonates take more warmth to break down as they move down the group.
• The carbonates grow more thermally stable as they progress along with the group.
• The difference in the stability of metal cation and oxide anion rises as the atomic number increases.
• As a result, because compact packing is not feasible, the stability of the breakdown product metal oxide reduces.
• As a result, the carbonate's stability improves.
• Thus, the order of thermal stability among the aforementioned carbonates is:

${\mathrm{MgCO}}_3<{\mathrm{CaCO}}_3<{\mathrm{SrCO}}_3<{\mathrm{BaCO}}_3$

So, option (B) is the correct answer.