Question

What happens when aluminium reacts with hydrochloric acid?

Answer 1

Hydrogen gas is being produced.

Explanation:

Aluminium metal will react with dilute hydrochloric acid to produce aqueous aluminium chloride, `"AlCl"_3`, and hydrogen gas, `"H"_2`.

The balanced chemical equation that describes this single replacement reaction looks like this

`2"Al"_ ((s)) + 6"HCl"_ ((aq)) -> 2"AlCl"_ (3(aq)) + 3"H"_ (2(g)) uarr`

Keep in mind that this reaction will not take place as soon as you add the piece of aluminium to the hydrochloric acid solution.

That happens because the piece of aluminium is protected by a layer of aluminium oxide, `"Al"_2"O"_3`, the same layer that protects aluminium from reacting with water.

The hydrochloric acid will take some time to eat through this protective layer, but once that happens, the reaction will proceed quite vigorously, i.e. hydrogen gas will start to bubble out of solution.