Talk:Avogadro's law

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The law as stated in this article is much stronger than I learned it in chemistry class. As I learned it, all Avogadro's law states is that the volume is proportional to the number of moles of gas if pressure and temperature is constant. It doesn't say anything about the relationship between the number of moles and the pressure (which would be a combination of Avogadro's law and Boyle's law) or about the relationship between the number of moles and the pressure (which needs Charles' or Gay-Lussac's law). It certainly isn't equivalent to the ideal gas law as this article seems to claim.

Agreed. Fixed. Hopefully :-) Vsmith 15:40, 12 Mar 2005 (UTC)

[edit] Why moles per volume is the same for all gases

It is remarkable that the volume of a mole of gas molecules is independent of the type (and I guess mixture) of molecules themselves. As a reader, I would very much like this article to provide an insight into why this is the case.AnthonyJamesWood 11th July 2006

That's a good question - I'll try to explain it as best I can:

I think it's best answered by understanding that the law only applies to a pair of volumes for which both the temperature and pressure are fixed. One volume (say hydrogen) at the same pressure and temperature will fill the same volume as an equal molar amount of nitrogen. In this case the nitrogen is heavier than the hydrogen molecules, but because it must have the same temperature and pressure as the H₂, its constituent particles must move a little slower (E_k=mv²). With the same temperature and pressure, it can easily occupy the same container as the other gas because it exerts no more force on the container walls, due to its particles moving slower, despite being heavier. If the N₂ molecules had the same speed as H₂, it would impact with greater force on the container walls and require a larger volume.

And just to relate the concept back to the other parameter, the amount of gas in moles, if we were now to take half the nitrogen gas away, it would only exert half as much pressure on the container walls (i.e. half as many collisions), and the container would collapse inwards significantly. Richard001 23:27, 25 December 2006 (UTC)