Question

which best identifies why the rusting of an iron nail in the presence of water and oxygen is an oxidation-reduction reaction?
water is a reactant
electrons are transferred.
nonmetals and a metal are involved.
energy is released.

Explanation:

An oxidation - reduction (redox) reaction is defined by the transfer of electrons between species. In the rusting of iron (\(4Fe + 3O_2+ 6H_2O = 4Fe(OH)_3\) which further converts to rust), iron atoms lose electrons (oxidation) and oxygen atoms gain electrons (reduction). The fact that water is a reactant does not define a redox reaction (many reactions have water as a reactant without being redox). Involvement of nonmetals and a metal is not the defining feature of a redox reaction (e.g., some metal - nonmetal reactions may not be redox if there's no electron transfer). Energy release is a characteristic of many exothermic reactions, not specific to redox reactions. So the transfer of electrons is the key feature that makes rusting a redox reaction.

Answer:

B. Electrons are transferred.