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Lecture 19. Gas Laws, Part 2
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Title  Lecture 19. Gas Laws, Part 2 
Title of Series  Chem 1A: General Chemistry 
Part Number  19 
Number of Parts  23 
Author 
Brindley, Amanda

License 
CC Attribution  ShareAlike 3.0 Unported: You are free to use, adapt and copy, distribute and transmit the work or content in adapted or unchanged form for any legal and noncommercial purpose as long as the work is attributed to the author in the manner specified by the author or licensor and the work or content is shared also in adapted form only under the conditions of this license. 
DOI  10.5446/18984 
Publisher  University of California Irvine (UCI) 
Release Date  2013 
Language  English 
Content Metadata
Subject Area  Chemistry 
Abstract  UCI Chem 1A is the first quarter of General Chemistry and covers the following topics: Atomic structure; general properties of the elements; covalent, ionic, and metallic bonding; intermolecular forces; mass relationships. Index of Topics: 0:00:15 Ideal Gas Law 0:06:32 Examples of the Ideal Gas Law 0:32:40 Density Calculations 0:34:24 Molar Mass Calculations 0:36:38 Density Example 0:44:30 Dalton's Law of Partial Pressures 
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00:09
so what you start with what we learned last time which is people the Nazis
00:16
also we talked about this and we Indiana example where we just have 1 set of conditions where where it is that once the conditions where gave you a yield of 3 of the conditions hostages the other 1 but that's that's useful for sure but there's another part of square what we have a whole 7 gas at 1 conditions and then we change what's going to happen and if we take a ballooning we pull it down how much of that going change the volume if we take a light bulb and turn it on and thereby making it up hell that interchange the pressure is that gonna break the white ball on if you are tired as go from here 0 degrees to 70 degrees something which is pretty normal in cold climates what's going to happen to them by the universe things like that and that's why the media so we can do all this and win the ideal gas so I started with a bad example here where we have a bubble blue of aluminum governments at sea level and ancestor in science and then we're going to raise up into the air so that there is less pressure there's less atmospheric pressure and temperature changes that somehow we're changing a couple of things were lowering the pressure which would do what increasing decreased the size of the bullet through lowering the atmospheric pressure the pressure around and then we're changing the temperature were making a colder so what happened decreased and we can see what's going to happen to us now How do you do that if I called the book think your book walking through this if have a bunch of different ways of using just boils lofted just Charles or you know in each 1 individually and that's fine but there's an easy way I think to remember heading toward you so that you don't have to make a decision which when am I going to use for each different situations In CDs just start with people that are to know what is already there is a constant is the variable since the concierges number so we could arrange this whole thing for people then to the right and 70 are so for some set of conditions whatever's on condition that maybe that's true excuse my computer glitches they alive and in the middle of reviewing the whole thing so it's been a little crowded wonderful viruses so you now that did not seem named for a different set of conditions any set of conditions it doesn't matter right just any sat in with the a radical thought and while is just a number and so this is equal and this is alarm well after the 2 of them equal to each other so soon after now we have the 1 the 1 over and when she won because due to the children to teach and we can do all of these ideal gas questions from this without having to make a decision about which set of equations are going to use so this is going to be really useful to you that you're going on starter for most things there's a couple of things I want to to point out that will hit some examples with what unit using pressure needs to be in here who or what have you been here 180 and wide you are the lady right are the art of the deal 100 atmospheres and so this has been a GM India had to be in and then I'll man was just moved into the was and also was kind of sad because we had the constant or in this Serbian union no 1 would come around here if we put pianist some units it's going to be in falling further pressure it's going to be the same unit sofa pressure and volume and Parliament you don't really need to worry about suppression by all the pressures of mines are multiplied by a by some Member Order to the different right if you're going from atmospheres to kill Pascal's the backandforth year they're multiplying dividing my number so the multiplied by the number of you multiply that by that number 2 so this is really nice because for this iteration you don't have to worry about your units to pressure the volume of and technically from owes you could have never actually was more likely you just always have holes but number items would be just fine because it can be converted to a number about times the number of moles it's just multiplying and dividing by number so if you multiply that by the end I 1 you would do that the other end now what about the do a lot of work last because she is plus or minus right you're adding or subtracting depending on what we're converting your adding or subtracting 273 solely because of that foster minus issue in your converting between Celsius Intel then you always have to put temperature and call of you cannot leave temperature itself so pressure volume in malls we don't have to be too picky about units when you're using this form when you using this form and you have to watch out yeah not sure you can always just converted to atmospheres leaders animals in the state that's fine that's idea that's OK but LCDs sometime on exams and does homework in general if you know when you're doing this at 765 millimeters of mercury you can leave it like that if you have 2 ml you leave like that but if you have 60 degrees Celsius to leave like that now so winter temperatures insults where you can do Sunday examining give you temperature and Celsius you're going to such talent so what's actually to go through and do this example so I walked through a little bit of it and will do it on the screen as well but it's useful sometimes To make good table like that and so I assure you that you've handed them out without necessarily having to write it all out when you get these
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hard changing multiple things as a lot of times a lot easier to just go ahead and write a little table of making sure that when you go to fill everything in your file notice when I film my damages and hearing here I was right in the plus 273 don't write down 1672 make a little table like this you'll feel it in soldiers right in the past to 73 or actually solid flesh but as usual I preferred it is a rigorous organization but so we have a lot of media and letting it would mean at the level of rise in 1 in what the new volume is so we start by just riding out this now we decide what isn't changing so did the temperature changing yes it is the pressure changing yes it's sea level at 1 were higher at point for is fired upon volume trading yeah that's the thing we don't know that they were selling for up to let the only thing here is isn't changing what's just cast out it's the same on side so it doesn't matter what it if it's 3 over here 3 over here the Council so that leaves us with that is not so we can survive surgery on you you know now it would have to be explicitly stated that it would have to to be something later on in the EU added another gas or something like that when we get into that a little bit more when we start doing on Dr. Dellums wall partial pressures and things like that were added in different gasses together but they have to say something we have to say yield I think it the next memory and it has like a bubble rising to the surface and were assuming that the most of change but they could say you know half of the moles of gas was lost that the water something like that they have but so we're left with there's no way this is where the little tables that I had opened that line would come in handy to go through actually write everything down have to but sometimes it's helpful and is going to go ahead and fell and so are P 1 is 1 atmosphere are 1 0 . 5 5 meters and then I turned the chair a 70 questions now we do the same thing for this service teach you is . 4 I don't know what the 2 is so we're just going to leave it the mariachi to to settle Calvin their serial number that switched it and we solve efforts now there's a couple of different ways of thinking about the discovered all line here this I feel that the numbers 1st year mostly because I think that's how people prefer to do it people in general you guys tend to prefer to fill in the numbers 1st personally I don't think that's the best way to do but I think the best way to do it is to rearrange a variable stars into to actually solve this 1st and so in that case you have it still is equal the P 1 of 1 over T1 52 comes up Peter comes down and so either way you and giving 1 . 3 3 but it's just In doing whatever we makes the least number of mistakes for you but give it a shot of waste unusual given a shot mostly in C which we like to see which way you make the most mistakes I think getting used to moving around the variables is probably the most useful way but I'm not going any better than you can always do it this way so you know where to find the snow that both are available and this will probably have to make less mistakes but I don't want so the next slide is just all wanted examples awards for the but soon now we have a lot of examples assume this would be useful to see how strong your glass have simulate ball to know whether or not the break because only about isn't just a filament Ray also has answered after on the way labeled works is that it has to be a abolished the up goal without actually combust and so you have oxygen in their air but so you have to put what we call an inert environment environment that is in that interact isn't going to react and so on and as that so open your light bulbs and this is what are incandescent light bulbs not the not the fluorescent ones but not so in order to do this you need to have Oregon in the tell you the pressure and temperature but they start out Of course what happens when you turn reliable 1 it gets hot especially the incandescent ones and they need to go through the same sort of and again you can just start from here can write this down without even having to give to watch part as to what you're doing to start off with and I say OK what isn't so what the situation is staying the same volume made it so that the light bulb glasses and a stretch out Frank well the animals are examining the Argonne Expedia coming in so we can cross those out In
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so you back now I haven't question right before class taking is actually kind of a good thing to bring up that this that talked about in reverse in 1 of the discussions where was 1 over in T 2 0 peaches isn't problem know the the ratio right so you could flip flop on you think about you know your algebra classes and cost multiplied by the Cheechoo comes up here in the T 1 comes up here key to go down here in the key 1 would go down there so these could be be inverted you could write this as 1 1 equals to 2 over the exceeding pt 1 over P 1 equals T overtly to and that's fine but I think it probably I don't like that your discussion because it international that easier sometimes of we're solving fours and the denominator it is actually a little easier to fulfill that by no means is mandatory but found it is useful to know and remember that that Harry Shields work but now we can go ahead we can tell everything and I'm going to go ahead and sell P to 1st and as I talked about before you welcome to go ahead and Gilfillan numbers 1st if you prefer give anything about rearranging your variables 1st is you can check forcing things at the end without having to check for .period and so will the easier and so we felt everything and we so we would know that whatever Glasser whatever system used to contain a lot of media will stand up to 1 . 4 3 aspects which here should be to the video for it but question so now we have a mobile of the film on a realistic think are you so let's if summoned him for dinner classified I reading that lets us but some of those renewed decisions by real fast so this year 85 18 now it's addition and so it's going to be to the ones places right so it would actually end up being 3 because it would be a whatever 273 was the fighters we're pulling out the ones place when the raid but unemployment went into a calculator of past so 358 so it's 358 and because its edition this isn't good remembering an addition actually because I wanted to forget about significant addition because this edition we hold out you would ever the lowest number of places which in this case is going to be a one's place and so this it's taken all the way up here once place and the same thing will happen here with this it's taken all the way out here once place so because of that this this and this will all end up with precincts the recent everyone not that and if there were more time because they know a different circuits therefore forgotten about so here here this To this condition so we go out to the place not a significant figure right said we use significant figures when we do multiplication division we do places when reviewing addition subtraction so the lowest number of places here is that you have the time than the 1 place so you have this and so it's they both go to the one's place so you can add it to the ones since a unit with because if this was an 80 inch 73 then you would only go to the kinds of yeah you certainly have to do is so when you go through same every stack is another is each on its own when you rearrange like this if it's all multiplication division of these Golos members expects if at all indigenous subtraction just below its number of places but whenever follows then you have to look at low cost so we started hearing me say I'm OK that's 358 and then we would go to the next 1 and we would say Well that's 291 and then what we're doing is we're taking this multiplying by that and dividing by that so it's recent figures times 3 6 divided by race and so it's you can refresher excessive revisited last year Life email and was worth between London and forcing things but in your last words really important analyzing things you lose a lot of points so that refreshing so we're almost 1 the deployment of it so now what so now I have a bubble and this is kind of like a balloon when it's an hour going from the bottom of the ocean up there at the bottom of a lake as well as all the way up to the top so we have a higher temperature changing Our pressure changing temperatures here pressure here and we want a normal volume so very much like the balloon problem so again we write everything else we start from here is a surname whenever he sees wondering to different conditions this is the 1st actors write this down then comes the house thinking that what here is changing the moles events so that leaves us with the 1 the 191 enacted so it will and of course to be 200 so now we sell for what we're trying to solve so what are we trying to solve the gym so we're solvent for this so we want to get back on own new little bit faster with this 1 so far stepbystep back the little 1 we're solving from the so we have P 1 he won where she won the and teach students multiplied the P2 divided down and so you have to now you fill in all your numbers now a little bit like this is that OK here I didn't miss let's go ahead and write everything down and then we will look at will see what we think OK so let's look at our units and hammock happy something down spoiler alert right 10 amid so much so that all we have atmospheres here atmospheres here so those would can cancel ahead when we are finally answer a loophole in here in Calvin Hill as those are going to have to walk what would that leave us with a view to cells in that anarchy volume unit yet so we have 14 months now we can't do that would tell them because again with the Calvin behind this issue of edition in addition and subtraction you can you can you have to remember that again thinking back to your algebra 2 days are over when this if we had you know something close 273 here found that really factored in writing and then factored in hearing factored in here to work that algebra Yukon just divided straight
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down like that in then you always have to go ahead and him but something like atmospheres of pastels millimeters of mercury or or any of those units although there does multiplying dividing by some number seeking legal because they would cancel here now know what if I gave you this is unity in pastels and this unit an atmosphere could you need those I know what you have to convert the same thing right and not which when you convert to a few converts something else entirely but they have to be the same so another little easier to see when we have a kind of written out like that whatever pressure pressure after being whatever volume and then in this case is where you're going to find if if we had both volumes they practically the same so whatever you need to fill in for pressure it's gonna be the same whatever their are whatever you need to fill in for volume it's gotta be the same if you're solving for 1 of those it's gonna come out to be the same thing put it we put in ML and so that's what we get we had both of these the atmospheres yes the unit conversions yes it's a should be on our agenda beyond the high equation sheet the whole way through shall be on there that 1 table and if it's not that doublechecking nature but 1
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last Wednesday when this but seeing formula In the gas is the athlete when mustard produces carbon dioxide and water so what what group is 1 group a study materials that want you here fundamentals if you get eligible problems and saplings almost annually with his limiting reagent thing I think I remember where I go for help that on your fundamental section so when you hear you balancing equations limiting regions of Maule the minds of most of geometry things like this This chapter for saying we taught you that fundamentals of Oral History review fundamentals and talk with this totalling 1 key highs wherever you go look there so when you get stuck on those problems make sure you know where to go for help and that's where you want it sold continuing on with us so we have to write out the equation so we can write out C 8 818 plus
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0 2 just this too 1st H 2 0 and now we felt now do we just go ahead and 2nd reading things and in doing their pressure calculations no balance that so you know he doesn't always sort of a guess and check sort of thing out probably by looked at this right away I'd say Well what to put in 8 years and see if it works and if we do that we would have our 16 oxygen so here we know that there is no way that we can get even number of oxygen I will actually thing and so go ahead and public in 9 here right because we balanced our 16 er 8 carbons balance are 18 hydrogen and then at that point you're gonna look and try to figure out a way to make this work and this is allowed Member I doesn't work so when you step like that and combustion probably do you double everything so this becomes 16 In this becomes 18 and every rewrite this too because it's a little messy at this point so that's the thought process China remembering on on how to go through this you just start looking at what you can balance In go from there if you look at the carbon 1st say probably in 8 that I think would be a 1st guests and you look here he said probably 9 of the 1st test of the new say there is no way to get this to work so I have to double Dublin but at that point now you have to worry about your oxygen and so you do whatever you need to do to the 0 2 about but so kind every going through the top process combustion reactions but to know that we have them we can figure out what's happening up here so we know the women there In Rome In the past we have 1 gram locked and we wanna know we're 1 gram of octane what volume of oxygen to replace so we're going to have to do some striking images were going to have to start with 1 gram of and we're going to have to get to something of oxygen was probably a good thing had to oxygen malls so can we just do GM to malls instantly better go through the mall's octane and when you get this number from periodic table now we have to go from walls of octane 2 moles of oxygen where read those numbers from the coefficients right creating them from here in here that's why we need a balanced equations now I want value so I'll just put in 22 . 4 this is a problem with that that tainted in the fundamentals so can I just in 22 . 4 leaders from all year on the New Haven wouldn't be in this chapter if that was all there was to it no 1 is that 22 . 4 all leaders from all what is the preferred to refer certain very special set of conditions as right so that we did this sort of thing the fundamentals chapter that was really all we knew how to do that was only when we cared about so every time that we gave you a problem like this we said at a City and then you don't really you're like OK invested the others do what they tell me to now we can do things on Asefi because we have the ideal gas so we have people that are too so we can go through it we can solve this for moles now we have moles we have pressure and we have temperature so can we find bodies that we can use this week sulfur so we plug in everything now In this case I did you atmospheres but right and Imojean pastels when you have to change it he asked why because of our ah and of course we have to always changer temperature so we feel about it and we get and check pressing things you
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can receive you have 3 so also OK questions on that yelling back not only so that is the question that problem 1 that is they knew we need a whole another you have most awful like every possible unit so you have to or 4 millimeters of mercury tore atmospheres pastels :colon Haskell's and that would be a little tedious so because it's easier in this case to just convert whatever is given in generating you that's usually that the method you wanna go and then what I'll give you you are an argument you into different units that of the 1 9 have appeared the . 0 8 to 1 of the leaders atmospheres for common and I'll give you the energy version of and those are really the only 2 versions of all but the question theoretically you could it just comes down to which was more work and more work to list out of all of the versions of art is to just converted it public now morning ,comma disorders of examples and things of that sort then the calculations so and then aged you kind of density means all that go revisit the fundamentals on it but the real quick review here so remember intensity is equal to mask divided by Bali solely you'll see it in units of things from a lot of times on board any sort of last year or over certain you Moeller density now that we don't talk about a lot but it's going be really useful here so it's density just as we call a density is grounds for about the king Tennessee Homola density as the most provide would instead of a useful you we always want to have to deal with GM that isn't the most convenient in the world to be calculating things with the right it's comedian allowed because you can measure it's Maciel the scoop out a sample while on a plate and enviable way but it's not very Nunavut calculations we always have to convert malls which luckily for us is not that big of a deal is just multiply and abiding by something when somebody can still use GM volatile now we want to be among the users Moeller density too because of what would be your unit here moles Over leaders can we hold our leaders using ideal gas I was sure we have people that party we have moles and we have volume so it will I a molar volume whenever we want all our mower density we weekend just assault and over me and we can end up with pillboxes and so is this is another unit that sometimes useful the work would end in useful to solve things for now Moeller mass calculations sold 1 of the things that we've kind of gone off and on throughout this court costs is selling for more massive different ways like the new the empirical formula and some other data and use offer them all and IDD in Imola massively empirical formula news often molecular urge the middle marker for things like that so we're going do some examples where we need to will between these 3 things Moeller mass density and events because know the useful thing here is to think about what you do the base in what you wouldn't want Seoul can we measure the density of substance grams per liter who are right and it theoretically could build some sort of set up with the scale around it and you can see how much a ghastly is on I think the really rudimentary version of this is you take a balloon antiterror the scale of the and and then you can blow air and you can see how much the airways of the EU can do this with pure gasses and Zamora allocation system to can we Moeller can lead to a more can we measure the density of us shocked that the only thing we can go through can measure that so now we can find the debt which invited differences and we can find the molar mask begin by animal amassed simply by measuring the stress thinks we can measure the density which invited measure the lower density and we can figure this out the militancy is a little bit harder to think about how you measure it that you can do it now you can't do that so few different weights and this is why I have these 2 slides you can do this by remembering these equations in manipulating these equations to get what you need or you can do it by looking at the moon on units which is why but the units appear again looking at the GM from all grams per liter and moles per liter and just saying what you need to move around what you need change around to get the right number to get the unit's struck whichever way you want to do it is find a different books different websites different people will show it all different ways but the the best way to explain this is by
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doing an example barring the little along examples of 1 I have access to the parents sat on to it so that has phase in this obviously the name that you'd have to know put is a colloquial term for the highly toxic gas Gaffney of a carbon oxygen and chlorine so we know that it's going to be some form of C O the Allred With you know something down here now I tell you the density but this what is the molar massive foster care so let's think about this issue we have pressure and temperature amino more density no 1 else can we solve or well the 1st is the winner of the density so let's go rearrange like I had on the slide will rearrange it for an overview I will see what we can fill in here that we know the density of milligrams per liter this will give us was a common His mulls over leaders so it's more than enough density will have more dense and went on the slide believing me from the moment is that you have to all those things you can soften the other and the other 1 was molecular Max so we were given the density were finding the molar density because we can measure all this experimentally and now we're going to solve for the law and then we're gonna solve Mormon of excess step 1 lamps offered and so we fell everything exactly as we've been doing being careful the units because there's a lot whenever there is a lot we have to watch the unit sorry from Argentina little squished by and were 298 so we solve this and redundant number now we have this that was given we have grams per liter and we have just that we found most now what is the unit for molecular because that's what we're trying to find need molecular mass till defines the molecular formula so we need the molecular mass we need to know the units 1 Michael MAK saying how many GM earned 1 mole so molecular mass unit is grounds so this is what we need we need to get grants from that's about all and so we have these 2 things that we naught for this grams per liter in the small for later What can we want GM on top right so we need to play around with units to make this work and so well I want GM and top so I'm and put the 4 . 2 4 and top right away before I really have to do too much thinking about 10 now I want more on the bottom 1 way have but Is it will open their leaders there you can have the leaders in their from all around smaller have the leaders unit in a bowl look what happens when you do this what happens to the leaders and that's all you'll find with any of these 3 things I talk about slide is you can use those 3 and you can you can move interchangeably between them by playing around with it and so when we get there we end up with that so that's a more so now now we know that we have that in because we're going in the right every time you won a molecular formula uranium OK now we're back to all those problems you love so much and were missing from the fundamentals so I know that you really missing them so I want to assure you that you don't see them again so this much carbon this must oxygen that much offer now how do we go about solving for considers is a couple of different ways you in the beginning a lot of times you solved for you had to assume that there is a hundred grand sample you can do that and that's finding of if you do it lowered the yield the there's there's a couple of things that come into play there is an easier way to do it in this case and that's to know that your molecular mass is 98 . 9 so then if I want know how much of that comment but went did multiplied by the per cent so that the easiest way to do this there are other ways but that is by far the easiest so where imitate each 1 of these Amorim multiplied by the person then again if you wanted to do the 110 simple thing that would work too now that gives a certain GM right do we want GM were trying to figure out a molecular formula now what we want also we
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have to take each of these convertibles good at a lower that it was prepare something go through we we can calculate all those numbers out we at 1 1 2 only apec somewhat as a new molecular formula CEO to now if you have gone through the 100 gram sample version of all you would amend up with what would you have ended up with at the end you wind up with an empirical formula and then you would have had a look at the empirical Mass and the molecular mass and compared them so you could do it that way I just think this was a little bit easier for where the this was the various subjective but are the starting on a little bit with best Dorland Wall partial pressure this is coming to play with mixtures where you have multiple types of gasses coming together so what's happened here is that each of you can treat each gas completely individual Inc which is really nice you can treat it as if you have 1 gas there and another gas in it it if you have to have expected infidelity of 1 definite container into all the calculations for that and inventory only the other gasses and do all the calculations for that and then use Adam together which is really handy so there the same with a little bit more formally told pressure of the mixture of gasses is the sum of the individual so if you have total pressure of 2 and you have 1 more you you have equal numbers of gas that means that you have 1 more 1 gas excuse me 1 of 1 gas when a team of another gas your total pressured me to that means if you had to atmospheres of 1 gas into atmosphere another gas total pressure would be 2 mysterious for some people this is the same this way now in reform but it it's enough that what I said I just ran out in terms of equation so it's not it's it's useful equation which is while the woman go over so pressure a pressure pressure that's just saying 1 gas cost another half plus another all of the pressures of you out among the people all so the exact that I was saying before and you have 1 atmosphere of gas 1 atmosphere of gas 1 atmosphere military arsenal atmosphere through 4th gasses from the atmosphere is told you but users adamant now what is pressure equal to Wellesley I don't ask for the people the Nazi so pressure is below the moles times are trained to overvalue rainfree freeze sold out so this is saying that while you could take you consult the pressure you could solve pressure its offer fashion maven Emily you can also do it properly you can say even doing 3 completely separate equations in 3 different parts of your paper and then add them all up to the end but you know if you know know the malls of all your gas and you know the temperature in the volume which Yukon and in anything about a community in Dublin Nigeria temperature in your volume and if they're inner container what's true about the temperature in the volumes for each gallon it's going the same it's not like it after they're going to sequester themselves in idea this quarter you take that on gasses don't know that so the gas is going to be spread throughout the whole computer so the all on the symbolic of the Alzheimer's and temperature because you can't have 2 different gasses mixed together at something he's already equilibrium and have the 1 gas will I'm going to be cooler than you that the vote would be there that wasn't meant to be a punch I'm so a lot already sold all this then is factored out right it took the and the inside wall is a constant in the Sky TV are going to be different from the Geneva gasses and is separated them out it said that so now if you want to know the total pressure you add up all your moles and you can do this city has multiplied by arts you really see you can use the ideal that for all the people that are and just use your total malls you have all your moles of all your nostrils fill in for and you can use either of asphalt just like you did before and will do some
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examples that next
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