# Ideal gas law and van Der Waals ?

P V = n R T

(atm)(L) = (mol)(L atm/mol K)(K) 1.Please show that all units for each variable in the van der Waals equation cancel out in the same way.2.What are the two main conditions or issues that are “corrected” in the van der Waals equation that are not included in the Ideal Gas Law?

### 1 Answer

- Dr WLv 73 weeks ago
ideal gas law

.. PV = nRT

VDW

.. (P + an² /v²) * (v - nb) = nRTnote

note the similarities?

.. an² /V² ... corrects for the assumption that there are no particle particle interactions

.. nb .. ... ..corrects for the assumption that gas particles have no volume

as to units

.. an² /V² must have units of pressure for dimensional homogeniety

... ... ... .. with the pressure term.

.. n² has units of mol²

.. V² has units of volume²

.. a must therefore have units of pressure * volume² / mol²

...... ex... atm L² / mol²

likewise...

.. b must have units volume / mol..... L/mol e.g.