Question

An element ‘A’ reacts with oxygen to form a protective layer of compound ‘B’. The component ‘B’ is also obtained by the reaction of ‘A’ with rust. The compound ‘B’ is known to react both with acids and bases. What is the element ‘A’?

Answer 1

Aluminum is a metal that can react with oxygen to form a compound known as aluminum oxide. Aluminum is more reactive than iron, which leads to the displacement of iron from iron oxide. Iron oxide is known as rust. Aluminum oxide is amphoteric which means it can react with both acids and bases.

Complete Step By Step Answer:
Iron is a metal with atomic number $26$ that can undergo loss of electrons which is termed as oxidation. Iron metal when reacts with oxygen gas undergoes oxidation and forms a compound known as iron oxide with molecular formula $F{e_2}{O_3}$ and is generally known as rust.
Aluminium is a metal that reacts with oxygen to form a protective layer, the molecular formula of a chemical compound that acts as a protective layer is $A{l_2}{O_3}$ known as aluminium oxide.
$4Al + 3{O_2} \to 2A{l_2}{O_3}$
Aluminium reacts with iron oxide which is generally known as rust to form aluminium oxide.
$2Al + F{e_2}{O_3} \to A{l_2}{O_3} + 2Fe$
Aluminium oxide $\left( {A{l_2}{O_3}} \right)$ is an amphoteric oxide which reacts with both acid and base as follows:
$A{l_2}{O_3} + 6HCl \to 2AlC{l_3} + 3{H_2}O$
$A{l_2}{O_3} + 2NaOH + 3{H_2}O \to 2NaAl{\left( {OH} \right)_4}$
Thus, element ‘A’ is aluminum. Compound ‘B’ is aluminum oxide.

Note:
Amphoteric nature means it consists of both basic and acidic properties. It also reacts with both acid and base. As aluminum is placed above in the reactivity series, it can be able to displace iron metal from rust and form aluminum oxide.