Magnesium can be used as a "getter" in evacuated enclosures, to react with the last traces of oxygen. (The magnesium is usually heated by passing an electric current through a wire or ribbon of the metal). If an enclosure of 0.382 L has a partial pressure of O2 of 3.5 x 10-6 torr at 27oC, what mass of magnesium will react according to the following equation?
The trick here is to identify the species for which we can immediately calculate moles. Here, we have P, V, and T for O2; from the ideal gas law, we can find moles O2. Once we have found moles O2, we convert moles O2 ---> moles magnesium, and then convert to grams magnesium. Here goes:
