Ideal Gas: Non-Uniform Conditions Explained

[mikeph]

Hi,

If I have a container with fixed volume, and fill it entirely with a known quantity of CO2, and then heat the edges, I should be right in saying I have under my control the temperature, volume and molecule number, and the pressure is fixed by the ideal gas equation (assuming the assumptions of this model are valid).But what if these values are non-uniform? Does the restriction still apply? Can I specify temperature, pressure, volume and molecule density fields, and is there some generalised for of this ideal gas equation?

Or can I say that in theory, the restriction has been lifted, and does not apply for a container with a gas which is not in thermal equilibrium.

Thanks,

 

[Dadface]

Hello Mikey .the volume of the gas will be the volume of the container and if the container is tightly sealed the number of molecules is fixed.If there is a temperature variation throughout the container there will be a corresponding pressure and density variation.The ideal gas equation is followed more closely when the gas reaches thermal equilibrium but it should be remembered that the equation is an approximation only and becomes more in error as the pressures rises and if the temperature approaches values where the collisions become exciting or ionising.

 

[mikeph]

Ok- thanks for your reply. Can I ask as a further question, if the ideal gas equation breaks down under those conditions, does a different equation (whether we know it or not) "take over"? Or am I free to vary the fields in whatever way I like, as long as I don't forget that I no longer have thermal equilibrium?

 

[Dadface]

As far as I am aware there is not an equation which applies closely under all conditions but there are equations that are better approximations.Van der Waals equation is an improvement on the ideal gas equation particularly for when gases get close to liquification.