Question

Hydration energy of the ion Al3+is three times greater than Ca2+. Why? ​

Answer 1

Explanation:

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+.

Answer 2

The hydration energy of the ion $Al^{+3}$ is three times greater than $Ca^{+2}$ due to the small size and higher charge.

• As the size of an atom decreases and its effective charge increase its hydration energy also increases because small cations are attracted by water molecules more easily than a large one.
• So, the hydration energy of the ion $Al^{+3}$ is three times greater than $Ca^{+2}$ due to its small size and higher charge.