A gas mixture has 2 atm #He#, 4.8 atm #Xe#, and 1.9 atm #O_2#. Which gas takes up the most volume in a total of 456 mL?
Interesting question, and I think your examiner is trying to be malicious. The answer required is that ALL the gases occupy equal volume.
Dalton's law of partial pressure clearly states that in a gaseous mixture, the pressure exerted by a component is the same as the pressure it would exert if it ALONE occupied the container.
So, given the above, to ask which gas occupies the most volume is a non-sequitir. All the gases occupy an equal volume, and, as stated, this volume is
PS I actually like this question, so I am going to steal it for my A2 class as a concept type of question to establish Dalton's Law. I bet it will fool most of the little blighters.