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

May 13, 2014

$\textcolor{b l u e}{2 {\text{Al"(s) + 6"HCl"(aq) -> 3"H"_2(g) + 2"AlCl}}_{3} \left(a q\right)}$

#### 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

$A l + H C l \to {H}_{2} + A l C {l}_{3}$.

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

$2 \left({\text{Al"(s) -> "Al}}^{3 +} \left(a q\right) + \cancel{3 {e}^{-}}\right)$
$3 \left(2 {\text{H"^(+)(aq) + cancel(2e^(-)) -> "H}}_{2} \left(g\right)\right)$
$\text{-----------------------------------------------}$
$2 {\text{Al"(s) + 6"H"^(+)(aq) -> 3"H"_2(g) + 2"Al}}^{3 +} \left(a q\right)$

Aluminum oxidizes as ${\text{Al" -> "Al}}^{3 +}$, while hydrogen reduces as $2 {\text{H"^(+) -> "H}}_{2}^{0}$.

If we add back the spectator ${\text{Cl}}^{-}$, we get:

$\textcolor{b l u e}{2 {\text{Al"(s) + 6"HCl"(aq) -> 3"H"_2(g) + 2"AlCl}}_{3} \left(a q\right)}$