What role does oxygen play in the rusting of iron?

In the process of rusting, oxygen plays a critical role in forming rust, which is primarily hydrated iron(III) oxide. When iron is exposed to moisture and oxygen in the environment, a series of chemical reactions occur. Initially, the iron oxidizes, reacting with oxygen from the air in the presence of water, and this reaction leads to the formation of iron ions. These ions then combine with oxygen to form rust.

Water acts as an electrolyte, facilitating the transfer of electrons during this oxidation process and allowing iron to lose electrons. The presence of oxygen is essential because it combines with the iron ions generated from the oxidation to produce rust. Thus, the correct response highlights the fundamental chemical reaction between water and oxygen that is crucial for rust formation.