Question

Why the hydration energy of Calcium is smaller than Aluminium

Answer 1

Mg 2+ has the larger hydration energy, because hydration energy increases with the charge on the cation and decreases as the size of the cation increases. Therefore answer is Na + .

Hope it's helpful.

Answer 2

Answer:

Now Al3+ and Mg2+ are nearly same in size. But the charge density on Al3+ is more than Mg2+ due to +3 charge on Al compared to +2 charge on Mg. Hence, hydration energy of Al3+ is more than Mg2+.