When elemental iron corrodes it combines with oxygen in the air to ultimately form red brown iron(iii) oxide which we call rust. (a) if a shiny iron nail with an initial mass of 23.2 g is weighed after being coated in a layer of rust, would you expect the mass to have increased, decreased, or remained the same? explain. (b) if the mass of the iron nail increases to 24.1 g, what mass of oxygen combined with the iron?