# Help with relationship of volume and pressure with real gases?

I've been trying to figure out this concept but after an hour of reading my text/googling I'm even more confused! According to Boyle's law p and v have inverse relationships when the temp and moles are constant, but my textbook says that for a real gas, attractive forces makes *BOTH* the p less and v less than the p and v of the ideal gas which really confuses me...

And if attractive forces make a real gas have a lower p than the p of an ideal gas, then am I correct to say that repulsive forces make real gases have a higher p than the p of an ideal gas, since the repulsion creates more collision with the walls of the container?

The v (of empty space) of a real gas is less than the the v of ideal gas (the volume of empty space) due to real gas molecules taking up volume. Then since the v of the real gas is less than the v of the ideal gas, does that mean the real gas's pressure is also less than the ideal gas's pressure?

Thank you so much for your help!

### 1 Answer

- davidLv 78 months agoFavorite Answer
part1 ... And if attractive forces make a real gas have a lower p than the p of an ideal gas, then am I correct to say that repulsive forces make real gases have a higher p than the p of an ideal gas, since the repulsion creates more collision with the walls of the container?

====== ??yes?? but what are these 'repulsive forces'? I have heard of several types of attractive forces between real molecules, but never heard of repulsive forces. ==== So your answer is a qualified yes.

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The v (of empty space) of a real gas is less than the the v of ideal gas (the volume of empty space) due to real gas molecules taking up volume. Then since the v of the real gas is less than the v of the ideal gas, does that mean the real gas's pressure is also less than the ideal gas's pressure? ... again --- yes.

Amanda .. What class are you taking?? For a freshman level Chem 1 class this appears to be overthinking Boyles Law. 99.99% of the time in those classes the prof expects you to ignore attractions and vol of the molecules themselves and just use the simple formula PV(before some change) = PV(after the change) with NO corrections for either effect because the effect is different for each different molecular substance.

===== just know that gases deviate from ideal behavior at high pressure (because the size of the molecules starts to make a significant difference) and at low temp (because the attractions start to effect volume as well).

Thank you for your help anyways!!!