ideal gas deviations

[jy777]

So, I am confused about this a little bit.

I understand that real gases deviate from ideal gases at high pressures and low temperatures.
I fully understand why as well.
The only trouble I am having is how the Van Der Waals equation is written.

If the volume of real gases is larger than that of ideal gases (because the high pressure causes the gas particles to become larger in size and thus, take up more room), why do we subtract nb from V (V-nb) in the van der waals equation?

Also, isn't it true that the "b" value will be larger for larger gas molecules? So that will make the V-nb even smaller when compared to the ideal gas.

Please help me understand where I am going wrong

Thank you

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[brood910]

So, I am confused about this a little bit.

I understand that real gases deviate from ideal gases at high pressures and low temperatures.
I fully understand why as well.
The only trouble I am having is how the Van Der Waals equation is written.

If the volume of real gases is larger than that of ideal gases (because the high pressure causes the gas particles to become larger in size and thus, take up more room), why do we subtract nb from V (V-nb) in the van der waals equation?

Also, isn't it true that the "b" value will be larger for larger gas molecules? So that will make the V-nb even smaller when compared to the ideal gas.

Please help me understand where I am going wrong

Thank you

Volume of ideal gases is larger than that of real gases, not vice versa.
For ideal gases, we assume that particles do not take up any of the space, but that's not true in reality.