Which substance is the oxidizing agent in this reaction? fe2o3+3co→2fe+3co2 express your answer as a chemical formula?

Equation is as follow,

                            Fe₂O₃  +  3 CO     →     2 Fe  +  3 CO₂

Oxidation:

                                        3 CO     →     3 CO₂

Oxidation state of C in CO is +2, and that in CO₂ is +4. So, carbon has lost 2 electrons per mole and 6 electrons per 3 moles hence,

                                 3 CO     →     3 CO₂  +  6 e⁻

Reduction:

                                    Fe₂O₃     →     2 Fe

Oxidation state of Fe in Fe₂O₃ is +3 per atom, and that in Fe is 0. So, Iron has gained 3 electrons per atom and 6 electrons per 2 atoms hence,

                                    Fe₂O₃  +  6e⁻     →     2 Fe

Result:
             Iron in Fe₂O₃ has been reduced in this reaction and has played a role of oxidizing agent by oxidizing carbon from +2 state to +4 state.

Ithink it’s 3 as the answer.

Yes it would be a physical change.