The reaction between HCl and Mg produces magnesium chloride (MgCl2) and hydrogen gas (H2). The chemical equation for this reaction is:

2HCl + Mg → MgCl2 + H2

In this reaction, HCl acts as an acid, donating a proton (H+) to Mg, which acts as a base, accepting the proton. The resulting products are magnesium chloride, a salt, and hydrogen gas, a colorless and odorless gas.