Which gas from the air becomes part of the product when iron oxidizes?

• A. Nitrogen
• B. Oxygen
• C. Argon
• D. Carbon Dioxide

Answer: (B)

Oxygen is the gas from the air that becomes part of the product when iron oxidizes. In rusting, iron reacts with oxygen from the surrounding air to form iron oxide, a solid compound. A simple way to see this is the common rust reaction: iron plus oxygen yields iron oxide (often written as Fe2O3). The other gases in air, like nitrogen and argon, are largely unreactive with iron under normal conditions and don't become part of the rust. Carbon dioxide isn’t formed in the basic rusting process either. So the oxygen you breathe is the component that actually ends up in the solid oxide.