80 likes | 269 Views
Nonideal Gases. Assumptions of Ideal Gases: The molecules of an ideal gas are very small, so their volume is assumed zero.
E N D
Assumptions of Ideal Gases: • The molecules of an ideal gas are very small, so their volume is assumed zero. • There is so much space between the molecules of a gas (as gases have little density) that the only collisions are with the walls of the container and there are no intermolecular forces between the molecules.
When would these assumptions fail? • If the volume of the gases was noticeable. • If the molecules collide with each other. • If the molecules have intermolecular attractions between them. • When would these failures occur? • Very low temperature • Very high pressure • WHY?
For a nonideal gas, PV=nRT does not work, so VanderWaals’ created:
“a” is a constant unique for every different gas, but in general it increases as the intermolecular forces increase “n” is involved because the more molecules there are the more intermolecular forces there are
“b” is a constant unique for every different gas, but in general it increases as the volume (size) of the molecules increase “n” is involved because the more molecules there are the more volume they take up
Typically nonideal behavior will only change the behavior of a gas about 5% from its ideal behavior, so “a” and “b” are really small values