# Deviation of real gases from ideal behaviour

From the Amagat's curve we can see two types of result for real gases.

1. If we increase pressure,the value of $PV$ decreases initially and then the value starts increasing for the gases like- carbon dioxide, nitrogen, oxygen, methane, etc..
2. If we increase pressure,the value of $PV$ starts increasing initially for the gases like - hydrogen, helium, etc.

Now please explain what're the reasons behind this kinda behaviour of real gases?

• This seems like a homework question. We ‎have a policy which states that you should show your thoughts and/or efforts into solving the ‎problem. It'll make us certain that we aren't doing your homework for you. Otherwise, this ‎question may get closed. – bon Jun 30 '15 at 17:53
• @Bon this isn't necessarily homework. I see it more as erratum. It does deal with something in the textbook, just that it doesn't look for an error. – M.A.R. Jun 30 '15 at 17:56
• I think it's just bad tag 'cause it doesn't look like erratum. – Mithoron Jun 30 '15 at 18:15
• @Mithoron I scratched my head for the tags. I, am the guilty fugitive who added erratum. Can you please add better tags? – M.A.R. Jun 30 '15 at 19:37