Which has more hydration energy? MgSO4 or BaSO4
△Hhyd = k1r+ + k2r−
observe that SO42− is a very big anion ⇒ r+ << r−
Thus,hydration enthalpy α 1cation size
∴ MgSO4 has more hydration energy.
In cases where r+ << r− lattice energy will not decreases rapidly with increases in cation size.But hydration energy will decrease rapdily with increasing cation size.
For solubility, hydration enthalpy > lattice energy.
∴ MgSO4 is more soluble than BaSO4