Question

Aluminium oxide, $A{{l}_{2}}{{O}_{3}}$is:
(A) Basic oxide
(B) Acidic oxide
(C) Amphoteric oxide
(D) Neutral oxide

Answer 1

Hint: Aluminium oxide $(A{{l}_{2}}{{O}_{3}})$ can react with both acids and bases giving rise to salts and water depending upon the medium it is placed.

Complete step by step solution:
Aluminium oxide is an inorganic chemical reagent with the chemical formula $A{{l}_{2}}{{O}_{3}}$. It is also called as alpha-alumina, alumina, alundum or aloxide. Well, aluminium oxide can react with both acids and bases and such compounds which can react with both acids and bases or the compounds which show both acidic or basic character are called amphoteric.
The presence of the other reactant in a reaction actually determines whether$A{{l}_{2}}{{O}_{3}}$ will behave as an acid or a base. It acts as an acid while reacting with base and as a base while reacting with acid thereby neutralizing the other and producing salts and water.
Let us consider an example,
-When aluminium oxide reacts with a strong base or an alkali like $NaOH$, it acts as an acid and forms a conjugate base ${{[Al{{(OH)}_{4}}]}^{-}}$which further forms a salt $Na[Al{{(OH)}_{4}}]$and water similar to an acid-base reaction.
$A{{l}_{2}}{{O}_{3}}+2NaOH+3{{H}_{2}}O\to 2Na[Al{{(OH)}_{4}}]$
-And when aluminium oxide reacts with a strong acid like $HCl$ solution, it acts as a base forming a conjugate acid ${{[Al{{({{H}_{2}}O)}_{6}}]}^{3+}}$ which further forms the salt $[Al{{({{H}_{2}}O)}_{6}}]C{{l}_{3}}$ and water like an acid-base reaction.
$A{{l}_{2}}{{O}_{3}}+6HCl+9{{H}_{2}}O\to 2[Al{{({{H}_{2}}O)}_{6}}]C{{l}_{3}}$
With dry $HCl$, the reaction will be,
$A{{l}_{2}}{{O}_{3}}+6HCl\to 2AlC{{l}_{3}}+3{{H}_{2}}O$.

Hence, the correct option is (C).

Additional information:
-Aluminium oxide is an inorganic chemical reagent which is also known by alumina or aloxide.
-It is found naturally as corundum, rubies, sapphires and emeralds.
-It is an amphoteric substance which can react with both acid and base.
-It is odourless and insoluble in water and occurs as solid and appears as white.
-Due to its hardness, is widely used and suitable to use as an abrasive. Also used as a catalyst, purification of water and as an electrical insulator.

Note: You can get confused with option (D) i.e. neutral oxide it is neither acidic nor basic. But amphoteric oxides are the oxides which can act as either acid or base depending upon the medium placed and aluminium oxide can react with both acid and base.