To calculate the number of electrons transferred during the electrochemical reaction, we need to look at the oxidation states of the elements involved in the reaction.In the given reaction:Mg s + 2H+ aq Mg2+ aq + H2 g 1. Magnesium Mg is in its elemental form with an oxidation state of 0.2. Hydrogen ions H+ have an oxidation state of +1.3. Magnesium ions Mg2+ have an oxidation state of +2.4. Hydrogen gas H2 is in its elemental form with an oxidation state of 0.Now, let's identify the oxidation and reduction processes:Oxidation: Mg s Mg2+ aq + 2e-In this process, magnesium loses 2 electrons and its oxidation state changes from 0 to +2.Reduction: 2H+ aq + 2e- H2 g In this process, two hydrogen ions gain 2 electrons in total and their oxidation state changes from +1 to 0.Since the number of electrons lost in the oxidation process is equal to the number of electrons gained in the reduction process, the number of electrons transferred during the electrochemical reaction is 2.