Final answer:
Oxygen (O2) is the oxidizing agent in the reaction 2H2S + 3O2 → 2SO2 + 2H2O.
Step-by-step explanation:
The oxidizing agent in the reaction 2H2S + 3O2 → 2SO2 + 2H2O is oxygen (O2). An oxidizing agent is a substance that gains electrons in a redox reaction, and in this case, oxygen is the species that is gaining electrons. The sulfur in hydrogen sulfide (H2S) is being oxidized to sulfur dioxide (SO2), while oxygen is being reduced, thus functioning as the oxidizing agent. This process shows that it is easy to oxidize sulfur in compounds such as hydrogen sulfide, making it a good reducing agent that, in the presence of a strong oxidizing agent like oxygen, can be further oxidized to various sulfur oxides such as SO32-, SO42-, or in this case, SO2.