Question

State which substance is undergoing oxidation and which substance is undergoing reduction in the following reaction:

Mg (s) + H2SO4 (aq) ---> MgSO4 (aq) + H2 (g)

Answer 1

Mg(s) = oxidized

H₂SO₄(aq) (hydrogen) = reduced

Step-by-step explanation:

Oxidized substances lose electrons and see an increase in oxidation number. Reduced substances gain electrons and see a decrease in oxidation number.

Lone elements always have an oxidation number of 0. H₂SO₄ and MgSO₄ are ionic compounds that can be broken up into a cation and polyatomic anion. The anion, SO₄²⁻, has an overall oxidation number of -2. Therefore, to make the overall charge of the ionic compound neutral, the hydrogen in H₂SO₄ has an oxidation state of +1 (bc there are two hydrogens) and the magnesium in MgSO₄ has an oxidation state of +2.

Since Mg(s) is losing electrons (goes from 0 to +2), it is being oxidized. Since the hydrogen in H₂SO₄(aq) is gaining electrons (goes from +1 to 0), it is being reduced.