In the oxidation reduction reaction 2FeCl2 + Cl2 = 2FeCl3 what substance is reduced? What substance is oxidized?

Iron is oxidized while chlorine is reduced.

Explanation:

The oxidation reduction reactions are called redox reaction. These reactions are take place by gaining or losing the electrons and oxidation state of elements are changed.

Oxidation:

Oxidation involve the removal of electrons and oxidation state of atom of an element is increased.

Reduction:

Reduction involve the gain of electron and oxidation number is decreased.

Consider the following reaction:

2FeCl₂ + Cl₂ → 2FeCl₃

in this reaction the oxidation state of iron is increased from + 2 to + 3. That's why iron get oxidized and it is reducing agent because it reduced the chlorine. The chlorine is reduced from - 2 to - 3 and it is oxidizing agent because it oxidized the iron.

2Fe⁺²Cl₂⁻²

2Fe⁺³Cl₃⁻³

The iron atom gives it three electrons to three atoms of chlorine and gain positive charge while chlorine atom accept the electron and form anion.