Gases have no fixed volume does that mean that one mole of any gas can occupy whole universe?

Question

First of all , how can one prove that gases have no fixed volume ? And if (though i know that it have) lets take a case . Take small amount of gas and fill it into a large box , about size of earth , consider that box has vacuum in it . The gas should fill all the earth but if does that , then the intermolecular attraction force should be inconsiderable or negligible at such large distances . What happen then ? There should be a limit to the volume ...

Another question is why molecule let H2 not attract another gas particle let He as there is same van der Waals force ........

Of course this isn't entirely true. The "normal" gas laws neglect gravity. Fortunately for us a sufficiently large amount of hydrogen gas in outer space can collapse into a star. — MaxW, Aug 13 '16 at 18:04

score 0 · Answer 1 · answered Aug 13 '16 at 15:14

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Gases have no fixed volume, if you put it in an infinite vacuum, a gas will at equilibrium have an infinite volume. You'll be waiting a while for it to reach equilibrium though. H2 will have some interaction with He, but it's very weak, so for most purposes can be neglected.

answered Aug 13 '16 at 15:14

MJCJM

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Why b/w he and h2 is weak force there but not b/w h2 and h2 – Prabhat Aug 13 '16 at 15:19
@dr.honey Yes there is also an attractive force between individual H2 molecules. – Dan Burden Aug 13 '16 at 15:49
Ya i know .....i want to know why only He-He has attraction but not in H2-He? – Prabhat Aug 13 '16 at 16:12
@dr.honey All gas molecules interact, but He-He interaction is weakest known. See comments here – Mithoron Aug 13 '16 at 20:47

Gases have no fixed volume does that mean that one mole of any gas can occupy whole universe?

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