Question

Mgco3 is more soluble than baco3 in water explain

Answer 1

Decrease in solubility occurs as we go down the group due to decrease in hydration energy as hydration energy is directly proportional with solubility..

BeCO3 > MgCO3 > CaCO3> SrCO3 > BaCO3

so MgCO3 is more soluble than BaCO3

Answer 2

There are more than one perspective of this answer.

The easiest is, down the group in periodic table, increase in radius of ion takes place. When MgCO₃ or BaCO₃ is added to water, it dissociates to form anion(CO₃⁻) and cation(Mg²⁺/Ba²⁺). Now the cationic part associates with the O₂⁻ of dissociated water molecule.

Now due to lesser size Mg²⁺ easily associates with O₂⁻ but Ba²⁺ doesn't because it has much larger radius than O₂⁻. Thus MgCO₃ has a higher solubility in water than BaCO₃.(Same theory goes for CaCO₃ also).

Now another theory considers the energy of hydration, increase in which leads to greater solubility in water. Down any group it decreases, thus BaCO₃ has lesser solubility than MgCO₃ in water.