Hydration energy is the heat evolved or absorbed when:

Explanation

Hydration energy is defined as 'the energy released when one mole of gaseous ions dissolves in water to give an infinitely dilute solution'. Infinitely dilute solution can be defined as the term in which a solution contains so much solvent that if one adds more solvent to it, there will be no change in the concentration of the solution. Attraction occurs between the water molecules and the ions of the solute, and the solute particles interact only with the solvent, not each other. Hydration energy is always negative, meaning it is exothermic and energy is always released.Option A is incorrect as an excess amount of water is required.