# Van der waals gas equation?

## Main Question or Discussion Point

Just wondering, for van der waals equation, the real pressure is smaller than the ideal pressure and the real volume is smaller than the ideal volume?

Borek
Mentor
Check - calculate P&V for several cases using both ideal gas equation and VdV equation.

Okay I found out that the real volume is indeed less than the ideal volume, but I don't get how the real volume is bigger than the ideal volume? I thought it would be the other way around because molecular volume becomes significant at high pressures meaning that gases have less free space to move around (because some of the space is taken up by the gas molecules themselves), and hence the real volume would be lower than the ideal volume? No?

Borek
Mentor
Okay I found out that the real volume is indeed less than the ideal volume, but I don't get how the real volume is bigger than the ideal volume?
This is a little bit convoluted and I have a feeling you are contradicting yourself - volume is less but you don't understand how it is bigger?

Ideal gas ignores molecule size, so at high pressures it theoretically compresses to zero, real volume is much larger than that.