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

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

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.