Question

A reddish layer of rust can form on old iron nails and bikes. In this chemical reaction, iron reacts slowly with oxygen in the air. The chemical name for rust is iron oxide. What are the reactant(s) and product(s) of this reaction?

Answer 1

Reactants: Fe,
`H_2O` and
`O_2`

Product:
`Fe_2O_3.H_2O`

Step-by-step explanation:

Two electrochemical reactions occur during the formation of rust;

1. Oxidation of iron (Fe) in water:
   `2Fe --> 2Fe^(2+) + 4e^-`
2. Reduction of oxygen in water:
   `O_2 + 2H_2O + 4e^- --> 4OH^-`

The two products from the two electrochemical equations then react together to form iron hydroxide.

`2Fe^(2+) + 4OH^- --> 2Fe(OH)_2`

The iron hydroxide thus produced slowly reacts with oxygen to form rust which is
`Fe_2O_3.H_2O`.

Hence, the reactants are iron (Fe), water (
`H_2O`) and oxygen (
`O_2`) while the product is rust (
`Fe_2O_3.H_2O`).