Hi, I went for a test today, and one of the problem was as follows:(can't remember the exact wording though) There is a sealed jar that is an insulator. It is divided in the middle with a piston that does not allow the 2 gases to mix, and is also a conductor. The piston has no mass and can move freely. The top of the jar contains 1.5mol of hydrogen gas, while the bottom contains 1 mol of oxygen gas. It is known that at 320K 1ATM, The volume occupied by the hydrogen gas is 4 times the volume occupied by oxygen. At what temperature will the hydrogen gas occupy 3 times the volume of oxygen? What I don't understand is how hydrogen can occupy so much more space compared to oxygen? Don't gases of the same mol occupy the same amount? Eg, 1mol of gas at rtp is 24 dm3, then 1mol at stp is 22.4dm3, so the H2 will occupy 1.5 times that of oxygen? I'm thing along the lines of PV=nRT, which don't really make sense to me. Or is it some other stuff, like graham's law or something? Any help will be greatly appreciated!