Question

In the reaction: `2H_2(g) + O_2(g) -> 2H_2O(g)`, what is the oxidizing agent?

Answer 1

The oxidizing agent is elemental oxygen.

Explanation:

And of course, the reducing agent is elemental hydrogen. Redox reactions may be formalized by notions of electron transfer, and assignment of oxidation states.

Elemental oxygen goes from oxidation state `0` to `-II`, and is therefore REDUCED; it formally gains electrons. Elemental hydrogen goes from oxidation state `0` to `+I`; it formally loses electrons, and is therefore OXIDIZED.