Question

Among the following compounds, how many are amphoteric in nature?

• A. $\mathrm{Be}{\left(\mathrm{OH}\right)}_2$
• B. $\mathrm{BeO}$
• C. $\mathrm{Ba}{\left(\mathrm{OH}\right)}_2$
• D. $\mathrm{Sr}{\left(\mathrm{OH}\right)}_2$

Answer 1

Answer: (A), (B)

$\mathrm{BeO}$

Explanation of correct options:

1. Amphoteric compounds are those compounds which can act as both acid and base
2. In other words, Amphoteric compounds can either donate its ${\mathrm{OH}}^{-}$ ion to Bronsted acid and also can accept lone pairs from Lewis base.

(A) $\mathbf{Be}{\left(\mathrm{OH}\right)}_{\mathbf{2}}$

Hydroxides of beryllium are amphoteric in nature, as it can react both as acid and base.

$$\begin{gathered} \mathrm{Be}{\left(\mathrm{OH}\right)}_2+2\mathrm{NaOH}\to {\mathrm{Na}}_2{\mathrm{BeO}}_2+2{\mathrm{H}}_2\mathrm{O} \\ \mathrm{Be}{\left(\mathrm{OH}\right)}_2+2\mathrm{HCl}\to {\mathrm{BeCl}}_2+2{\mathrm{H}}_2\mathrm{O} \end{gathered}$$

(B) $\mathbf{BeO}$

Oxides of beryllium are amphoteric in nature as it can react both as acid and base.

$$\begin{gathered} \mathrm{BeO}+2\mathrm{NaOH}\to {\mathrm{Na}}_2{\mathrm{BeO}}_2+{\mathrm{H}}_2\mathrm{O} \\ \mathrm{BeO}+2\mathrm{HCl}\to {\mathrm{BeCl}}_2+{\mathrm{H}}_2\mathrm{O} \end{gathered}$$

Explanation of incorrect options:

(C) $\mathbf{Ba}{\left(\mathrm{OH}\right)}_{\mathbf{2}}$

Hydroxides of barium are not amphoteric in nature, it can form alkaline solution in water, hence it cannot react both as acid and base.

(D) $\mathbf{Sr}{\left(\mathrm{OH}\right)}_{\mathbf{2}}$

Hydroxides of strontium are not amphoteric in nature as it cannot react both as acid and base.

Hence options A and B are correct, as the oxides and hydroxides of beryllium are amphoteric in nature.