Question

What happens when a piece of aluminum metal is added to dilute hydrochloric acid?

Answer 1

We need to know that when the aluminum and hydrochloric acid is reacted, there is a formation of both aqueous and gaseous products. The aluminium is a metal which has properties like malleability, ductility and it is silvery white in color. Aluminum is a good conductor of electricity and it has an amphoteric character. Because, it is reacted with both acid and bases. When it is reacted with acid, there occurs a displacement reaction.

Complete answer:
As we know that when the acid reacts with hydrochloric acid, there occurs a displacement reaction and there is a formation of salt of aluminum and gaseous hydrogen. The aluminum and HCl are reacted at room temperature. And the aluminum is dissolved in the hydrochloric acid, gets aluminum chloride and hydrogen gas. This reaction is an irreversible reaction. Hence, the products will not react with each other and this reaction is an oxidation – reduction reaction. The step – by – step reaction can be written as,
$A{l^0} - 3e \to A{l^{3 + }}$
The cation present in the HCl gain these electrons and it reduced to molecular hydrogen,
$2{H^ + } + 2{e^ - } \to H$
The whole ionic reaction is,
$2A{l^0} + 6{H^ + } + 6C{l^ - } \to 2A{l^{3 + }} + 6C{l^ - } + 3H$
Hence, the complete reaction can be written as,
$2Al + 6HCl \to 2AlC{l_3} + 3{H_2}$

Note:
When the aluminum metal is reacted with hydrochloric acid, there is a formation of salt of aluminum which is aluminum chloride and hydrogen gas by displacement reaction. And the product will not react further. Because, the reaction is irreversible. And this reaction is known as oxidation – reduction reaction. Which means, here both oxidation and reduction process takes place.