Answer:
Cu
Fe
Step-by-step explanation:
Oxidizing agents:
Oxidizing agents oxidize the other elements and itself gets reduced.
Reducing agents:
Reducing agents reduced the other element are it self gets oxidized.
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.
a) Cu²⁺ (aq) + Mg(s) + Cu(s) + Mg²⁺(aq)
Copper is oxidizing agent it accept two electrons from magnesium and oxidize the Mg and itself get reduced.
b) Fe₂O₃(s) + 3CO(g) → 2Fe(l) + 3CO₂(g)
In this reaction iron is oxidizing agent because iron itself reduced from +3 to 0.