[Chaggi]

So the question basically asks of the 5 assumptions of the kinetic theory, and which one is false under a non ideal condition.

My problem is almost how it's stated and a bit on how van der Waals corrects for this.

The two assumptions that bug me are

1) Molecules have negligible volume
2) Gas particles only interact with each other during collisions (basically no charge, just *Ignore me, I am impatient*)

So during high pressure situations, I think that volume needs to be calculated in. Because pressure and volume are inversely related, when pressure goes up, volume goes down. This leaves less space for molecules, so you can't leave their volume out of the calculations out. I think I'm fine up to this point.

However, when you adjust using the van der Waals equation, don't you assume that it's repulsive force that acts (since it's volume that decreases, things get tighter). There shouldn't be anything to do with attractive force because interactions still only would happen with each other during collisions.

The other side to this story can be that since you have to adjust for van der Waals, because as pressure goes up, Z goes up. To bring Z back down to ideal, you need to have attractive force instead of repulsive.

Something like that?

[Borek]

OK for the volume, not sure if I understand the other piece, although you are right that assumption that molecules don't interact doesn't hold too well when they are close.