What else is produced during the replacement reaction of magnesium and hydrochloric acid?

MgCl₂ and H₂

Explanation:

The reaction between Magnesium and Hydrochloric acid is a single replacement reaction. In a single replacement, a metallic ion replaces another ion based on their positions in the activity series.

The reaction can be written as:

              Mg + HCl → ?

The ionic form can be written as:

             Mg + H⁺ + Cl⁻ → ?

Now lets look at the reaction halves:

            Mg → Mg²⁺ + 2e⁻        This is an oxidation half in which 2e⁻ is lost

           2H⁺ + 2e⁻ → H₂         This is a reduction half in which 2e⁻ is gained

In the activity series, Mg is higher up and is able to replace the hydrogen ions that in the lower part of the series.

Combining both reaction halves, we have:

               Mg + 2H⁺ → Mg²⁺ + H₂

If we include the spectator ions we have:

             Mg + 2HCl → MgCl₂ + H₂