Question

Name an element from Group 2 which forms an amphoteric oxide and a water-soluble sulphate.

Answer 1

Beryllium forms oxides of the formula BeO. All other alkaline earth metal oxides are basic in nature while BeO is amphoteric in nature i.e., it reacts with both acids and bases.

BeO is amphoteric based on following reactions:

$BeO+2NaOH\to N{a}_{2}Be{O}_2+H_{2}O$

$BeO+2HCl\to BeC{l}_2+H_{2}O$

Sulphate of beryllium is a white solid which crystallises as hydrated salt $\left(BeS{O}_4.4H_{2}O\right).$

$BeS{O}_4$ is is fairly soluble in water due to the highest hydration energy of the metal ion in the group.

Hydration energy is more than lattice energy and so it is readily soluble. Down the group, hydration energy decreases and hence solubility decreases for sulphates.