0:01okay so up until now we spent a lot of time talking about
0:04ideal gases but it turns out that no gases
0:07are actually ideal and all the ideal gas law gives is a pretty accurate idea
0:12what's going on
0:13there are slight deviations when we're talking about a real gas
0:17and so what I wanted to use on a review the conditions Ivan
0:21ideal gas we'll see where these deviations for real gases
0:24occur and first we said in an ideal gas is one
0:27that has molecules that don't occupy any actual space
0:32so no actual space in a real gases particles
0:36do you occupy space it's a microscopic I'm outta space but its real in a Dutch
0:41chemist named JD Vandewalle
0:44actually study this deviation so van
0:47dear wall I'm and he also found that
0:51on light ideal gases real gas particles do you exert
0:55a small amount have I'm force on each other in these forces were actually
0:59named after him we call them Vandewalle forces now so
1:02Vandewalle found that the degree to which a real gases deviates
1:07the freemen ideal gas has a lot to do with the magnitude of the intermolecular
1:12forces
1:13and this size at the particles Celestron
1:16assisted him in and let's fill it with some particles
1:20and what do you think is happening if all the particles
1:24in this container are slightly attracted to each other
1:28well in a small way that gas is gonna be
1:31imploding are caving in on itself circadian
1:34in on itself because all these particles are a little bit attracted to each other
1:39and what do you think this is affecting
1:40what's gonna fact the pressure because now
1:44the gas isn't pushing out on the side to the containers much as we thought it was
1:49so for real gas pressure we need to be able to correct
1:52for the intermolecular forces but that's kinda tricky because we gotta think
1:56about what the intermolecular forces are dependent on
1:59and purse I say that takes in these courses is dependent on the
2:03concentration
2:04other particles because more particles means more attractions at a
2:09concentration in
2:10anything is just the amount at that thing per the space that it occupies
2:14and the Malabar particles on the moles in the space that they occupy
2:19is the ball I'm so the concentration
2:22is the malls per volume and in divided by
2:26BR malls providing would be alright if we're talking about all of these
2:30particles
2:31being attracted 21 particle but they're all actually being attracted to each
2:35other as well
2:37so although these particles are also
2:40attracted to each other and what that means is that the force
2:43actually increases exponentially as particle concentration increases and so
2:48we need to make it
2:49in divided by the square now this is kind of a little bit of a crazy thought
2:53but the thing that characterizes
2:56the intermolecular forces between particles is actually
2:59different for different particles and so we need to account for the different
3:03characteristics
3:04at different gases and Adams that are in their particle so each gas
3:08has a different intrinsic factor that we need to consider and we call that
3:13and a and we can to give a as the attraction coefficient but it's usually
3:17evaluated
3:18given to us in a table because its unique for the gas is that we're dealing
3:22with it so
3:24putting these thoughts together we find that the p.m. ideal
3:28the pressure idea is actually equal to the pressure observed
3:31plus this consideration and the attraction called coefficient times the
3:36concentration
3:37at these particles square now it's important to make no
3:41that the forces may attract each other these these particle forces
3:45may attract each other in causes and Canada implode
3:48but they might also very well repel each other and so if they repel each other
3:53the value-add a wood being negative so it can be positive
3:57or negative depending on whether the particles are attracted or repulsed from
4:01each other
4:02and this makes pretty logical sense if you think about it because the pressure
4:06we observe is an understatement i do. pressure
4:10edged it's a system is slightly imploding
4:14so we we need to add this correction it's an exaggeration
4:19an ideal gas if the particles are repelling from each other in
4:23impressing out on the underside even more and in that case
4:27we will need to subtract the correction serve Vandewalle Tatas
4:31to correct for the intermolecular forces when we're dealing
4:35with the real gas mother other deviation was related to the size the particles
4:40and the free space
4:42the day take up which affects the value for are ideal
4:46volume so each gas has particles that are a little different size again
4:50depending on
4:51Adams or the Marshall Center in Madagascar hydrogen particles
4:55for example are quite small but if we're talking about methane particles
4:59well as a quite a bit bigger and so each gas is an impure call volume factor to
5:04consider for we call this
5:06factor B and I usually think Ive be as mine
5:10bigness coefficient be for bigness so we consider the size and molecules
5:15and we also have to factor in how many many particles molecules or atoms
5:20their RN and matches are moles
5:23or in so we multiply the moles by our biggest coefficient and we can write
5:29this as an equation
5:30if we say that the volume ideal that their
5:34ideal volume is the bomb at the container
5:37minus this space op occupied by the particles
5:42which would be in times be and as another quick note unlike
5:46a be. what always be positive because the marchers were always take up some
5:51amount of space
5:52Asus starting with the ideal gas law which is
5:56PE is equal to it in RT
5:59let's insert are correct in I pressure for real gas are corrected volume for
6:04real gas
6:05into the equation so starting with are corrected pressure we know that the
6:09ideal pressure is equal to the pressure observed
6:13plus our attraction coefficient times are
6:16our concentration are more concentration squared
6:20so PE observed plus eight times
6:23in over the square and then we can insert are
6:27volume so the ideal my name is actually equal to the volume
6:30the container minus the
6:33the number of particles times the bigness coefficient RB
6:38so VC minus in be in the corrected
6:42product have the at the real pressure in the real volume
6:46now is equal to in RT so by correcting for the intermolecular forces
6:51and Anna Boehme that's taken out by the particles now we have an equation
6:56that applies to real gases which we call the banner walls
6:59equation and it looks pretty terrifying there are
7:03tons a values in here but it's really no big deal because the only difference
7:06between this
7:08and the ideal gas equation is just the corrected
7:12pressure in the corrected volume