Question

Which of the following is an amphoteric hydroxide?
(A) $Sr{(OH)_2}$
(B) $Ca{(OH)_2}$
(C) $Mg{(OH)_2}$
(D) $Be{(OH)_2}$

Answer 1

In order to find which of the following is amphoteric hydroxide, we must first know what an amphoteric substance is. Amphoteric substances are those substances which can react both as acid and as a base.

Complete answer:
Let us understand about amphoteric substances. Amphoteric substances are those substances which can react both as acid and as a base. Amphoteric species are also known as the amphiprotic molecule which can either accept or donate the protons. These amphoteric substances will react in order to give salt and water. The amphoteric hydroxide can act both as acidic as well as basic hydroxide. Elements which are neither high electronegative nor high electropositive will form an amphoteric hydroxide. The amphoteric hydroxide will act as an acid or as a base depending on the reaction condition. The metal hydroxides with highly charged central metal atoms are amphoteric oxide or amphoteric hydroxides. Some metals such as the aluminium, zinc, tin, lead and beryllium can form amphoteric oxide or hydroxide. These hydroxides will form amphoteric hydroxide based on the surrounding substances pH.
Now let us move onto the given question.
Option (A) $Sr{(OH)_2}$will act as basic hydroxide. Therefore, it is an incorrect answer.
Option (B) $Ca{(OH)_2}$will act as basic hydroxide. Therefore, it is an incorrect answer.
Option (C) $Mg{(OH)_2}$will act as basic hydroxide. Therefore, it is an incorrect answer.
Option (D) $Be{(OH)_2}$will act as both acidic and basic hydroxide. Therefore, it is a correct answer.

Hence the correct answer is option (D).

Note:
We have to remember that the $Be{(OH)_2}$is an amphoteric hydroxide which is used for the following purposes such as
- For the Beryllium-metal alloys
- Copper-beryllium metal alloys.