[tumblewush]

Last week we had a dry lab session with regard to real gases and we had to do do some calculations, comparing experimental isotherms and that obtained using the equations of state. Everything was going well, the lab exercise mainly involved the use of the Van der Waals equation. Then the class was divided into groups and assigned a different equation of state and we landed up with the Modified Berthelot, which is shown below:



The gas used in the exercise is carbon dioxide. I have all the critical constants which I got from the 9th Ed. of Atkins, but that P in the right side of the equation is really bothering me (the one to the right of the 9). Some sources say that it's the absolute pressure of the gas, but they haven't given anything in the exercise in relation to CO₂ at 31.1 and 100 degrees celsius, so I have nothing to work on. There are two tables given, one for the experimental isotherm and the other for the van der waal's isotherm. We have to make a separate table for the modified berthelot isotherm, but we're missing that value for P. I was thinking that it'd be RT/V but that just can't be. Can you guys help?

[AWK]

P on both sides has the same meaning.