Question

Aluminum hydroxide, ${\rm{Al}}{\left( {{\rm{OH}}} \right)_{\rm{3}}}$ is insoluble in water, but dissolves readily in both acidic and basic solutions. Such behaviour is characteristic of:
A. Amphoteric behaviour
B. A buffer
C. Hydrophilic behaviour
D. None

Answer 1

Hint:
Hydroxide of aluminum, ${\rm{Al}}{\left( {{\rm{OH}}} \right)_{\rm{3}}}$ can accept electrons as well as donate in basic and acidic conditions respectively.

Complete step by step solution
We know that dissolution involves interaction between solute and solvent, in this case ${\rm{Al}}{\left( {{\rm{OH}}} \right)_{\rm{3}}}$ and water but it is insoluble in water. However, when it is added to an acid or base it gets dissolved easily. We can take its addition to dilute ${\rm{HCl}}$ and ${\rm{NaOH}}$ for example for which we can write the following chemical equations:
$
{\rm{Al}}{\left( {{\rm{OH}}} \right)_{\rm{3}}} + {\rm{HCl}} \to {\rm{AlC}}{{\rm{l}}_{\rm{3}}} + {{\rm{H}}_{\rm{2}}}{\rm{O}}\\
{\rm{Al}}{\left( {{\rm{OH}}} \right)_{\rm{3}}} + {\rm{NaOH}} \to {\rm{NaAl}}{\left( {{\rm{OH}}} \right)_{\rm{4}}}
$

We can say that it can act as an acid by accepting electrons as well as a base by donating electrons. This definition of acids and bases was given by Lewis and it encompasses those substances also that do not have proton or hydroxyl group but can still act as acid or base.
When a substance can act as both, acid as well as base, the behaviour is known as amphoteric behaviour. It is also shown by \[{\rm{A}}{{\rm{l}}_2}{{\rm{O}}_{\rm{3}}}\] which is an amphoteric oxide and behave in the same manner.

Now, for the other given terms, a buffer is a solution which is resistant to change in ${\rm{pH}}$ when we add a small amount of acid or base to this. For another term, we can understand hydrophilic behaviour as its name suggests hydro means water so hydrophilic means water-loving. We encounter this with hydrophobic which means water-hating in soap’s cleansing action.
Hence, we can safely conclude that the correct option is A.

Note:
In addition to ${\rm{Al}}{\left( {{\rm{OH}}} \right)_{\rm{3}}}$ or \[{\rm{A}}{{\rm{l}}_2}{{\rm{O}}_{\rm{3}}}\], we have many other species that show amphoteric behaviour such as oxides of zinc and lead.