When iron is exposed to moist air, the surface of iron rod chemically reacts with oxygen to form rust (Fe2O3⋅×H2O). Chemisorption is the process in which, the reaction between the adsorbent and the adsorbate takes place. In rust formation, water in the atmosphere is adsorbed on the surface of the iron and this water molecule takes part in the reaction. Hence, rusting is an example of chemisorption.