Answer to Question #55352 in Physical Chemistry for Ojimi

Question

Rusting is an example of what reaction?

Answer 1

Rust is an iron oxide formation in reaction with oxygen, particular case of corrosion. It is a complex process which in very simple manner can be written as:
Fe²⁺ + 2OH^– → Fe(OH)₂
4Fe(OH)₂ + O₂ + 2H₂O → 4Fe(OH)₃.
Products are dictated by the availability of water.
Rustling of iron is referred to oxidation reaction but in presence of water and especially electrolyte (solutions of salts and so on) it occurs as electrochemical process. Its key reaction is
O₂ + 4 e^- + 2 H₂O → 4 OH^-
And iron (reducer) provides electrons for oxygen reduction.

Answer: rusting is an example of oxidation