MHT CET Chemistry Question (2026) — Solution

Step-by-step solution

The thermal stability of alkaline earth metal carbonates increases down the group from Be to Ba. This is because as the size of the cation increases, its polarizing power decreases. A smaller cation like Mg^ 2+ polarizes the large carbonate ion (CO_3^ 2- ) more effectively, weakening the C-O bond and facilitating its decomposition into the metal oxide and CO_2. The order of thermal stability is MgCO_3 Therefore, MgCO_3 has the lowest thermal stability among the given options and decomposes most easily. Answer: MgCO _3