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Write reactions to justify the amphoteric nature of aluminum.

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Hint: Amphoteric compounds are the compounds which can react with both acids as well as bases. Along with aluminum, copper, zinc, tin, lead is also amphoteric in nature. These metals usually form amphoteric oxides or hydroxides.

Complete answer:
We know that species which react with both acids as well bases are amphoteric in nature. To prove the amphoteric nature of aluminium we have to show the reaction of aluminium with acid and base. Reaction of aluminium with an acid is as follows:
$2Al\left( s \right) + 3{H_2}S{O_4}\left( {aq} \right)\xrightarrow{{}}A{l_2}{\left( {S{O_4}} \right)_3}\left( {aq} \right) + 3{H_2}\left( g \right)$
This is how aluminium reacts with an acid. Metals react with acids to liberate hydrogen gas.
Reaction of aluminium with base:
$2Al\left( s \right) + 2NaOH\left( {aq} \right) + 6{H_2}O\left( l \right)\xrightarrow{{}}2N{a^ + }{\left[ {Al\left( {O{H_4}} \right)} \right]^ - }\left( {aq} \right) + 3{H_2}\left( g \right)$
This is how aluminium reacts with base.

Additional information:
Properties of aluminum: Aluminium is a lightweight metal, it is non-toxic, it has good strength. Aluminum is corrosion-resistant. This is because when aluminum is exposed to air it forms a protective layer of aluminum oxide on its surface. This layer prevents this metal from corrosion. It has good conductivity of heat and electricity, it is malleable and ductile. It is used in a variety of products. It can easily withstand the carbonation pressure due to which it is used in making cans (beverage containers). It is used in making aircraft as well because of its lightweight and high strength. It is used in making windows and doors as well.

Note:
The diagonal relationship is said to exist between certain pairs of diagonally adjacent elements in the second and third periods of the periodic table. According to this relationship, diagonal elements will possess the same properties. For example properties of lithium resemble properties of magnesium, beryllium resembles aluminum, boron resembles silicon, and so on.

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