What's the difference between these two questions?
Hi there! As we know, gases don't exist as ideal gases but as real gases. Ideal gas uses PV=nRT as its equation while real gases uses Van der Waals equation, it's kind of similar to the ideal gas law but there are some modifications. Another things is that VdW equation uses a series of constant for gases which is present as variables a and b.
So instead of using the simple PV=nRT, we will use a more complicated equation whenever we want to use the real gas equation. I attached the formula of VdW gas equation. Hope that clears things up!