Question

Amploteric hydroxides react with both alkalies and acids. Which of the following Group 2 metal hydroxides is soluble in sodium hydroxide?
(a) $Be(OH{)}_2$ (b) $Mg(OH{)}_2$ (c) $Ca(OH{)}_2$ (d) $Ba(OH{)}_2$

Answer 1

Answer: (a) $Be(OH{)}_2$

The solubility of hydroxides of alkaline earth metals increases from Be to Ba, in water $Be(OH{)}_2$ and $Mg(OH{)}_2$ are almost insoluble.
Due to high hydration enthalpy and high lattice energy

$Be(OH{)}_2$ is not soluble in water $Be(OH{)}_2$ is an amploteric hydroxide. With acids, $Be(OH{)}_2$ is neutralised giving salts.

$Be(OH{)}_2+2HCl⟶BeC{l}_2+2H_{2}O$
$Be(OH{)}_2$ reacts with NaOH also forming beryliate.
$Be(OH{)}_2+2NaOH⟶N{a}_{2}Be{O}_2+2H_{2}O$