Question

According to law of conservation mass can neither be created or destroyed so why the mass of iron increases when it reacts with oxygen to form rust?

Answer 1

This can be visualized by considering the formation of water from oxygen andhydrogen molecules: Notethat the hydrogen and oxygenatoms simply rearrange themselves but are not destroyed. Thereofore massis conserved. ... For exampleiron rust by combining withoxygen to form rust (ironoxide).

Answer 2

When an iron nail rusts, it seems to get heavier in mass. cause rusting is an exception to the Law of Conservation of Mass.