Question

How can I balance this chemical equations? Aluminum and hydrochloric acid react to form aluminum chloride and hydrogen gas.

Answer 1

`color(blue)(2"Al"(s) + 6"HCl"(aq) -> 3"H"_2(g) + 2"AlCl"_3(aq))`

Explanation:

This reaction is between a metal and an acid which typically results in a salt and the release of hydrogen gas. The unbalanced reaction is

`Al + HCl -> H_2 + AlCl_3`.

This is a redox reaction, whose half-reactions are and become:

`2("Al"(s) -> "Al"^(3+)(aq) + cancel(3e^(-)))`
`3(2"H"^(+)(aq) + cancel(2e^(-)) -> "H"_2(g))`
`"-----------------------------------------------"`
`2"Al"(s) + 6"H"^(+)(aq) -> 3"H"_2(g) + 2"Al"^(3+)(aq)`

Aluminum oxidizes as `"Al" -> "Al"^(3+)`, while hydrogen reduces as `2"H"^(+) -> "H"_2^0`.

If we add back the spectator `"Cl"^(-)`, we get:

`color(blue)(2"Al"(s) + 6"HCl"(aq) -> 3"H"_2(g) + 2"AlCl"_3(aq))`

I hope this was helpful.