Question

What are amphoteric oxides? Give two examples of amphoteric oxides.

Answer 1

Hint: Oxides are the chemical compounds that form by the combination of oxygen and any other elements. In oxides, the oxidation state of oxygen is ${ -2 }$ or we can say the valency of oxygen in oxides is ${ 2 }$ whereas the valency or oxidation state of other elements may vary.

Complete step-by-step answer:
-Acids are compounds that lose protons or accept a pair of electrons in solution. Bases are compounds which gain protons or lose a pair of electrons.
-Amphoteric oxide is an oxide that reacts with both acids and bases. In other words, it possesses both acidic and basic properties.
For example both zinc and aluminium are metals but their oxides, ${ ZnO }$ and ${ Al }_{ 2 }{ O }_{ 3 }$ are amphoteric oxides as they react with both acids and bases.
The following reactions will take place:
${ Al }_{ 2 }{ O }_{ 3 }{ +6HCl\rightarrow 2{ AlCl }_{ 3 }{ +3H }_{ 2 } }$
${ Al }_{ 2 }{ O }_{ 3 }{ +6NaOH+{ 3H }_{ 2 }{ O\rightarrow 2Na }_{ 3 } }{ Al(OH) }_{ 6 }$
${ ZnO+2HCl\rightarrow { ZnCl }_{ 2 }{ +H }_{ 2 }{ O } }$
${ ZnO+2NaOH+H }_{ 2 }{ O\rightarrow Na }_{ 2 }{ [Zn(OH) }_{ 4 }{ ] }$

Additional Information:
-Normally metals form oxides that are basic in nature and non-metals form oxides that are acidic in nature. It is a property of the element and does not depend upon any external factors.
-Amphoteric nature: It is related to having the characteristics of an acid and a base and capable of reacting chemically either as an acid or a base.
Example- Water is amphoteric - it is able to act as either an acid or a base.
At a pH of ${ 7 }$ (neutral), the concentration of hydroxide ions is equal to that of hydrogen ions. If the equilibrium is disturbed, the solution becomes acidic (higher concentration of hydrogen ions) or basic (higher concentration of hydroxide ions). Water can act as either an acid or a base in reactions.

Note: The possibility to make a mistake is that only metals or nonmetals can act as amphoteric oxides but both metals and non-metals can act as amphoteric oxides.