On what factors do hydration energy & solubility depend ?
Does the hydration energy increase with increase in solubility ?
Hydration enthalpy may be define as, energy change when one mole of ionic compound get dissolved in water. when an ionic compound is dissolved in water, ions from compound form a kind of temporary bond with water molecule. Solubility of a compound is depends on the co-relation between lattice enthalpy and hydration enthalpy. If the hydration enthalpy is equal to or greater than the lattice enthalpy, then the salt is water soluble.
Factors on which Hydration enthalpy depends :
1)size of cations and anions : As the atomic numbers increases, ionic size also increases, leading to a decrease in absolute values of enthalpy of hydration.
2) Charge on cations : As the charge on cation is more hydration enthalpy is more.For example hydration enthalpy for Mg2+ will be higher than hydration enthalpy of Na+.