What is #P_2O_5#?
Well phosphorus pentoxide is a dense free-flowing white powder, that has a melting point of
It reacts with water to give phosphoric acid.......
........and in fact it is so hygroscopic, that when you use a tin that has been already been opened, you find a syrupy crust of phosphoric acid that you must dig beneath to get at the good stuff.
The molecular formula is