Now remember that the van der Waals equation is used for real gases. You'll notice that there's no purple box because you're not expected to memorize it. If you do have to use it on an exam, it's usually embedded within the question or on a formula sheet. So if we take a look here, we say that for the van der Waals equation it is pressure plus your moles squared times your van der Waals constant A divided by your volume squared. Because this portion contains our van der Waals constant A. It is a correction.

More attractive forces or just the polarity, general polarity of gas molecules? Then that's going to be times volume minus your moles N times your van der Waals constant B, because B is involved here. This is a correction for the volume of gases which can be tied to their size. Now this equation may not look like it, but it's connected to your ideal gas law. The van der Waals equation is used for real gases. The ideal gas law is used for ideal gases, but ideal gases are imaginary.

If ideal gases existed, postulate one says that their volume is so small that it's insignificant and not important. It's negligible. So since they're so small, that means their size would be equal to 0. And let's look if an ideal gas is involved, B is 0, so N * 0 is 0. This would mean that this entire part here is just V. And then if we're dealing with an ideal gas, an ideal gas has completely elastic collisions. It has no attractive forces or repulsive forces, so its polarity would be equal to 0.

So take that zero and plug it in. So N2×0/V2, all that just becomes 0. So all you have left is P. So if we're dealing with an ideal gas, the van der Waals equation simplifies into the ideal gas law. So that's the connection they have to one another. Now if we take a look here at the columns we have all these gases. The second column are our A values and they're in units of atmospheres times liter squared over mole squared. And then here we have B. Here their units are liters over moles.

With polarity or attractive forces, it's harder to see a pattern, but remember B is our size coefficient we set. As the molecular weight increases, your value for B increases. So if you were to look and look at all the weights of each of these gases, it would make sense in terms of the numbers as you see them more or less. There's a few deviations of course, because it's chemistry. But the general trend is as you increase the weight of a gas, you should see your B value increase as well.

Alright, so that's how our van der Waals equation is connected to the ideal gas law, and this long equation is the van der Waals equation. Again, don't worry too much about memorizing it. It's more important to understand the ideas of the coefficient A & B.