What are the products of the following reaction? #2Al(s) + 6H^+ (aq) ->#

1 Answer
Jul 2, 2016

Answer:

Aluminium cations and hydrogen gas.

Explanation:

You were given the reactants in the net ionic equation that describes the reaction between aluminium metal, #"Al"#, and hydrochloric acid, #"HCl"#.

Hydrochloric acid is a strong acid, which means that it dissociates completely in aqueous solution to form hydrogen ions, #"H"^(+)#, which you'll very often see referred to hydronium cations, #"H"_3"O"^(+)#, and chloride anions, #"Cl"^(-)#.

#"HCl"_ ((aq)) -> "H"_ ((aq))^(+) + "Cl"_ ((aq))^(-)#

You can thus rewrite the equation as

#2"Al"_ ((s)) + 6"H"_ ((aq))^(+) + 6"Cl"_ ((aq))^(-) -> ?#

Remember, the stoichiometric coefficient of the hydrogen ions must also be distributed to the chloride anions, since

#6"HCl"_ ((aq)) -> 6"H"_ ((aq))^(+) + 6"Cl"_((aq))^(-)#

Now, when aluminium reacts with hydrochloric acid, it gets oxidized to aluminium cations, #"Al"^(3+)#. At the same time, the hydrogen ions get reduced to hydrogen gas, #"H"_2#.

#2"Al"_ ((s)) + 6"H"_ ((aq))^(+) + color(red)(cancel(color(black)(6"Cl"_ ((aq))^(-)))) -> "Al"_ ((aq))^(3+) + color(red)(cancel(color(black)(6"Cl"_ ((aq))^(-)))) + "H"_ (2(g)) uarr#

As you can see ,the chloride anions are spectator ions, which is why the initial equation didn't include them

#2"Al"_ ((s)) + 6"H"_ ((aq))^(+) -> "Al"_ ((aq))^(3+) + "H"_ (2(g)) uarr#

Now all you have to do is balance the aluminium and hydrogen atoms

#color(green)(|bar(ul(color(white)(a/a)color(black)(2"Al"_ ((s)) + 6"H"_ ((aq))^(+) -> 2"Al"_ ((aq))^(3+) + 3"H"_ (2(g)) uarr)color(white)(a/a)|)))#

The products of the reaction will thus be aqueous aluminium cations, #"Al"^(3+)#, and hydrogen gas, #"H"_2#.

If you want, you can add in the chloride anions to get

#2"Al"_ ((s)) + 6"H"_ ((aq))^(+) + 6"Cl"_ ((aq))^(-) -> 2"Al"_ ((aq))^(3+) + 6"Cl"_ ((aq))^(-) + 3"H"_ (2(g)) uarr#

This is equivalent to

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

The single replacement reaction reaction between aluminium metal and hydrochloric acid produces aqueous aluminium chloride and hydrogen gas.