A tank contains 480.0 g of oxygen and 80.00 g of helium at a total pressure of 7.00 atm. Calculate the following: a) Moles of O2 in the tank. e) Mole fraction of He. b) Moles of He in the tank. f) Partial pressure of oxygen. c) Total moles in the tank. g) Partial pressure of He. d) Mole fraction of O2.