How do you determine the oxidizing agent in a reaction?
The oxidizing agent is the species that accepts electrons.........
.........and thus is the species that is reduced in a redox reaction.
If we look at, say, the combustion of coal:
Zerovalent oxygen gas oxidizes zerovalent carbon to give
And of course we can artificially split these reactions up to give separate oxidation/reduction reactions, for instance,
And overall, we simply sum the reactions directly:
And thus, again, the oxidizing agent is the brute that accepts electrons, which here is clearly?