Add to Watchlist

Lec. 14. Corrections, Midterm Postmortem, Free Energy and Equilibrium


Citation of segment
Embed Code
Purchasing a DVD Cite video

Formal Metadata

Title Lec. 14. Corrections, Midterm Postmortem, Free Energy and Equilibrium
Title of Series Chemistry 1B: General Chemistry
Part Number 14
Number of Parts 18
Author Shaka, A.J.
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 non-commercial 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 10.5446/19465
Publisher University of California Irvine (UCI)
Release Date 2012
Language English

Content Metadata

Subject Area Chemistry
Abstract UCI Chem 1B General Chemistry (Spring 2012) Lec 14. General Chemistry Intermolecular Forces -- Corrections, Midterm Postmorterm, Free Energy, and Equilibrium -- Instructor: A.J. Shaka. Ph.D. Description: UCI Chem 1B is the second quarter of General Chemistry and covers the following topics: properties of gases, liquids, solids; changes of state; properties of solutions; stoichiometry; thermochemistry; and thermodynamics.
will have the grades posted this cost and the exams are being scanned and so you get back if there are any mistake on your the sun many e-mail on exact mid-term too and what it is and then I have a copy so I can look at it and fix it and that will post all the updated scores for mid-term 1 and to but look don't sit on midterm you and come to me after I'm out of town at the end of the quarter and say there is a spoof on midterm you I waited 2 weeks to find out about Talbot yourself out of this scorers nature there's no mistake on your that there are we can fix on the weights later it's much more difficult it has a kid I love reading stories I particularly like reading the Greek minister about 1 reported ancestors and I liked reading about all the pagan gods because they like data versions of what I wanted to be a powerful they get in fights with each other like I did with my sister and I wish that I could turn into a spider something and I guess I sort of like personally because I like the idea of being strong but my favorite character was unpaid on this as the myth goes was the son of Mother Earth and another 3 gods and he was arrested but here's the metaphor spontaneous could never be because every time he threw down to the ground the test Mother Earth he came back strongly that's the metaphors that you need sometimes in life things don't always go your way they don't always go your way the 1st time they may not go your way for a long time but the difference is whether you give up where you come back stronger that makes a world of difference in the long run without a mind I want to kind of go over a postmortem on some of the problems that I created that I saw In mistakes on I toyed with the idea of the following if on the final you have those distributions of speed and you draw out wrong at the time this I just postural 3 than grass as evidence that he learned nothing at all don't let that happen that's a two-second problem and I'm going to go over it now so make sure you get it right it's not that important but it's kind of a metaphor for actually paying attention and learning was supposed to do 1st I wanna
start lower some correction some of figured out on your own that I made a grew when I analyze the energy density of octane and hydrogen and a goof is big enough it was a simple mistakes that all shy but like the Mars orbiter has a big impact so of hydrogen is not nearly as bad that is what I sketched out from 41 to let 1st fix my mistake and here was the problem I said supposedly we want transition to a hydrogen what volume of hydrogen gas in a thousand years signed 25 Celsius is required to produce a saying he and the combustion is 25 gallons of octane and then you get the density of arcane and its standard in the office of combustion 50 500 from all their children and here's what went wrong right here involved what I
originally put made no sense but I I put it the unit's canceled out so that was OK but I got the ratio wrong it's 1 is 114 grams not 114 moles as 1 and by putting the 114 on I got a factor of 12 thousand and that makes a huge difference in how practical you might assess hydrogen could be so let's go through it now and get it right so with this ratio correct but 1 killer is 114 kilograms then we have 582 moles of octane in 25 gallons and if we work that out we get 3 . 2 million killer jewels but I think before we had a much much bigger numbers With this 3 . 2 million we have to figure how much we would get from hydrogen for hydrogen we get 240 1 . a killer jewels from all just from the end of the formation of water vapor and remember I said I was using water vapor it doesn't matter as long as you use that and that means that when you convert it to the malls of hydrogen you need to
get 1 . 3 2 times tender before 13 thousand malls of hydrogen that's quite a lot but it's not a million people so I have to do with and then we had to
figure out the volume and now the volume comes out to be something much more reasonable because the number of malls is not so cute we get 47 60 who later therefore the hydrogen gas review we would have to be about 50 times larger the the volume of gas but it was meant to be a review of the horror no I mean set on 3 sides like the giant and you know that makes quite a bit of difference In addition we don't have to burn the high if we use the hydrogen and fuel cell then we can extract energy from hydrogen much more efficiently because we don't make an internal combustion engine works by exploding and making the expansion and whenever you make the because once you make the you can't extract all the energy that the you make something very disorder and there's only so much water you cannot back out of for the 2nd loss but if you don't make the if you make it work for us by converting the hydrogen and fuel cell to electricity that can be far more efficient and so we might I doubt will be affected 50 out of that will get something of them and that means that it might be possible the big problem right now where the
hydrogen is the best kinds of fuel cells use platinum as a catalyst to make the fuel cells go and because these platinum it's like paving the roads with golden extremely expensive and many that had appreciable amounts of platinum as part of the car and that's where chemists have come and find a better solution the fuel cell it only uses she stopped and that doesn't need to run an elevated temperature the problem with a fuel cell is to get the rate to be good enough you have heated up and that he has to come from somewhere probably from your car batteries but you still lose by having the heat that thing up all the time in order to run has been quite strong To get an appreciable rain and right now there doesn't seem to be a solution for that have a fuel cell that runs more like a battery of tests it's their room temperature and runs and loses electric power for your card use OK now let's go over a few John there were still
areas on the floor Of that the relative numbers of Adams versus argon and helium at 25 Celsius we didn't grade on the exact shape of the curve but there are 0 Adams moving at 0 speed because moving and 0 speed means you're a solid and there is no solid in there so the curve starts at 0 but then comes out and then you have to die out again 0 it can't keep going up because it keeps going up here find that there is a time and energy from somewhere make those molecules he going faster and faster and there isn't it's at 25 Celsius that has a finite amount of energy that depends on the
temperature so we wouldn't want that let them have a look them this was
162 62 before they all started 0 they all had a maximum somewhere and the heavier you are this lower your your Mac your most probable speed is the most probable speed is the highest point on the I think the problem I said I was around 1100 reviewing right they dropped from 0 1100 and that you got something goes back in and you can draw roughly symmetric it's not going America roughly the distance from here to here and the distance from here to work those back down to almost 0 is about the same this because John we have very accurate 1 gone there's argon here because we know that the most probable vehicles like the square root of the more that but you know the most probable speed healing for 4 grams or more 1100 you can take the ratio Of the square root of masses and
figure out exactly where the system you can drop you like when we don't want to do is drop .period understanding of the game here someone to the right because that was the headed guy is moving faster than it can possibly be you just think about collisions between them and the heavier guy guy doesn't get knocked around nearly as much the same 3 like I said it's still not moving very fast OK let's go on well I just
want to say again the death it was Maxwell who worked out that this particular distribution maximizes the entropy so it's the most probable and we have all the masses if you want to practice just take the function this is basically got out of the square and then need of a minus some number of times the square just plot next squared times needed the minus the 6 square and
look at new CIA started 0 it goes up and then the exponential the and function kills it Peter from going too fast this 1 it was a weak .period
the papers I created 1 person got this right I great every single paper but I did write a lot because I like to see what people do and only 1 person of the 1 greatest which was about 50 the let them make sure that this problem makes an encore appearance that we get it right we were supposed estimated at the end of the of combustion of propane using the bond and stock OK I tried to declared by writing the history of the and then that CH women that CH 3 what the structure would be rather than just writing C 3 trade with a little but the actual structure if you write about looks exactly like this you know two-dimensional schematic form of course is the three-dimensional molecule and the bond angles are not 90 degree the tattered Federline angles and form the 3 D structure and move it can move around like spaghetti but for the purpose of analyzing and all we need is there we count 1 2 3 4 5 6 7 8 th bonds that we have the bread and to C C bond that we have the break and then were asked to yeah Delta page for some reaction 9 here's the thing whenever you write a state functions doesn't delegates whatever if you're referring to a chemical reaction right
down the reaction that gives you kind of fixed point to refer to what reaction of my talking about here many people just figured out how much energy it took the bus the thing apart but that's not what I'm interested in I'm interested in the development of combustion which means I'm reacting this with oxygen and producing CO 2 1 8 2 0 so there's a lot more to it just breaking this thing apart and added that not the reaction we're talking about if you don't write down the reaction of Liu and I'll forget what you're talking about yourself and you start hitting the wrong there and I think that may have happened for some people so they generate
calculations for the wrong react that's the rest the so Delta native combustion refers to a reaction always write down the reaction and that balances Adam Stone appear and disappear in chemistry they just rearrange that's all they do the nuclei and penchant for nuclear plants are thick and it's just the electrons to move around and rearrange just like the the letters in the jungle we did our 6 it's just that 1 makes a word and the others nonsense we start here by saying right were burning C 3 H a propane with oxygen there were producing C O 2 and to that's what complete combustion me we have 3 comments here and this products side the only molecule of carbon His O 2 so we have to put a there we have a hydrogen the only molecule tighten on this side it is 2 0 so we have to put a floor there and then we count up the number of oxygen is we've got 6 and this is molecular oxygen we have to put up a fight there and so now we want to break apart the reactants and the products into Adams and then figure out which side when 1st estimated how much energy it takes to to break the the reactants formerly into added we know where I am going to do that but remember the beauty of state functions In the past doesn't matter so the staff can be fantasy because the fact of the matter it doesn't have to to be something we can really do it can just be anything that we can figure let's figure let's break this apart hinted 3 carbon atoms in the gas phase 8 hydrogen atoms in the gas phase and 10 oxygen atoms in the gas sphere well I have to break 8 ch bonds to C bonds and 5 oxygen double bonds and you're given all those on the front I think that used the same number 8 times 412 plus 2 times 348 that's the Carver lost 5 times 496 to break these apart this reaction To make this go on paper require 60 472 killer jewels from more it takes a ton of energy to break all those bonds apart OK I have that number now what I want to do this go to the other side in a fight balanced it on demand the same Adams but I have to count on different kinds of bonds because here I O H fonts and derided him annually bonds and here I have the strong see all double bond and
I didn't have any of those over here so we have to take a look that's how those pan out and see what we get for that let's do that yeah
we have to again count the bonds each C O 2 has C O double bonds organize 6 of those each of these has to always single bonds organ at 8 0 and we get the same ad the the question is whether it takes more energy to break the products apart Adams or the reactants apart and because of the very strong carbon-oxygen double bonds this number 7 43 years the winner In those days we get 6 times 743 plus state and it turns out always sponsor pretty good too 463 so we get 81 62 go jewels from all on this side and now I'm going to go over this very carefully because I have a lot of questions Is it reactants my products the wise it's different for this and that what I wanted to hear it is just go over there so that you can get screwed up trying to remember if it's reactants mines products in his mind that it's hopeless what we want to say I've got add these reactions somehow In however I added my it's got to total up to the reaction I want not some other reaction of left field once I've gotten so that they add up to to what I want it'll be absolutely clear which one's negative and which ones not and there's nothing to remember the less you have to remember the better off you are especially as you get older because your memory will not be a if you're only strategy To learn things is somehow remember directions you're going to be cold can you have to just learn how to figure them out yet remember something of course but you don't have to remember the details of the reaction that we want is this 1 and you see but the C O 2 is on the right hand side where is the CEO to use on the left-hand side here on the previous slide that the propane was on the left-hand side so the propane thing going to Adams is fine last whatever it was this 1 however I've got turned around backward otherwise I won't have O 2 on the rise and therefore I have to change the side of this 1 I don't give a toss which is products reactions here I'm just saying there's an easy way to see what have to be and that's the way to remember not by saying over this and that this that so we have to turn around this product Adam isolationism imaginary reaction were forced to turn it around and when we turn a reaction around when the initial and final states along the signing of the state functions for the reaction also slot because that's just the right
man at the left and the final change them it changes the side therefore this 1 is going to become negative simply by the fact that I have to turn this reaction around to get the 1 I want so let's do that with :colon
that let's leave this 1 as it is we figured that 1 54 72 this 1 around and now we see that all the items go away all these imaginary things go away and when we add up to chemical equations we get the reaction we want it's balanced the way we want and now we see we're gonna take 64 72 -minus 81 62 the way I think of it I'm always adding but the I hadn't changed the sign but this 1 from 1 I figured as I figured it the other way around so I write Imus plus and I change the sign of any reaction but I turned around I don't even think of subtract I always had every but some numbers are negative then there is the right answer 60 knots at 1690 killer jewels from all yes I'm going to go over that on the next few slide it depends whether you're talking about bond and felt whether you're going to this imaginary intermediate where broken all the bonds or not 10 all were doing we are not saying that this reaction actually occurs nobody is proposing that we can do this in the labyrinth of this ever happened but the beauty is it doesn't matter if it happens or not as long as we got number where it's not word if if I go to the top of Mount Everest and then come back and on my a comeback since the last sentence since the fire that was where I was before and it doesn't matter that I didn't actually go Grant In fact based on reason news reports you don't want to go to Everest unless you want .period end up with a very short life here's my thought than it's it's not worth trying to remember we're trying to to remember which gets the negative side because it'll be obvious when you just add among if you cancel out all the things either it'll be the reaction you want or it'll be some mumbo jumbo that you don't want and then you have to figure out which ones you turn around but you just have to find reactions that add up to the ones that you want now we can also do this problem a different way a more accurate way we could use the heats of formation the Member of the bond and obvious on average and it depends what kind compounds were included in the average what I the average score for this exam this was pretty good actually I think I never look at the average but just marking the paper would be a much higher for this class then it would be if I just gave it every registered voter and since I don't know exactly which compounds that are included in the series and so forth I expect
stalling the approximate that's not not not accurate now let's try it another way then using heats of formation let's try another imaginary have to get to what we want I suppose we were
given the same problem well we had the heats of formation of propane C O 2 an H 2 0 and remember that the formation and the formation of molecular oxygen he is 0 0 because the heats of formation are from elements in their standard states made the molecules it's me he said that we would get if we we did that imaginary reaction but these can be measured in many cases and so they're much more active for the heat of formation of propane now I've got a different reaction I don't have gas phase I have elements In the standard state at 298 . 1 5 killed In the elements that are 3 carbon in the form of graphite as a solid I should probably Poland s ,comma Grafite here graphite is a solid plus for molecular hydrogen not hydrogen atoms molecular hydrogen is hydrogen in the standard state at 298 . 1 5 Calvin this hypothetical reaction if I could carried out and make propane this way which I cannot gives and in some of the of minors 104 . 6 killer jewels from all How do I know that I have to lift that up I don't know and on an exam of course you have to be given all the heats of formation of every single compound in a chemical equation otherwise you can't do the problem and I can I can do the same thing with C O I can't imagine taking 3 graphite and 3 molecular oxygen and making 3 carbon dioxide molecules the standard stay at 9 and but since I've made 3 I have to take 3 times delved into formation because Delta a formation of C O 2 it is Her mole of C O 2 and I'm making 3 but at 3 times as much that's my industry 93 . 5 I think we've seen that small figure before and I have to multiply that by 3 I keep this sign and that's the last thing I have to me is water and to make water I take for hydrogen as molecular hydrogen and 2 molecular oxygen for water molecules and I have to look up the Delta major formation of water and I the multiplied by 4 and I have 4 times -minus 241 . 8 now if I wanted 5 were to say Well what about the
oxygen the combustion reaction that's a reagent how would I make oxygen from elements in the standard state I naked from oxygen I'd start with 0 2 however many I and I make all too I do not and so delegates for that is 0 because that both sides of the same path to to be 0 we even if I write it down if both sides of the same as to be 0 so then I I realized that I don't need that 1 for this approach using formation because I'm using the elements not imagining going which is not the same as the L. and if I use them this broad here the
here's the difference the products that we need are already on the right hand side because we made them from the elements we made C O 2 and its 2 on the right hand side but the reactant propane was also on the right hand side and therefore I have to switch this around because I want this guy on the left hand side that's all turned this chemical equation around and I changed this from my minus what a minus sign in front of it because I turned it around and before it was minus 104 . 6 therefore for for for this reaction written this way it's a plus 104 . 6 and I think the plus sign just that emphasized and therefore for this reaction that we wanted we have propane and that means we already have on the right and this is 0 we take we had this equation and the other 1 so we take 104 . 6 last 3 times minus 393 . 5 for this guy "quotation mark 4 times minus 241 . 8 for the Water and if we do that we get -minus 204 3 . 2 killer jewels from all of which you see is pretty far off from the other 1 more
than 10 per cent off I would trust this number much more but keep in mind when you do that you're imagining doing the combustion at 298 . 1 5 if you actually burning propane in a flame you have to be careful because the temperatures not to 98 . 1 5 in a flying it's potentially far higher the that and you would have to correct for that by knowing all that heat capacities Of all the products and reactants and then I would be much more detailed factual figure OK so just Rock always right down the reaction you want put together anyway you want like Tinker Toys all the things apart depending what information you have if you have dealt of formation for all the things involved always use that because it's more accurate if you don't the estimated with the bond and help build In the ballpark but you can't assume but that's going to be an accurate figure "quotation mark there's a summary know what
reaction dealt in ages referring to by whatever the definition it for Vonn Damm top isn't breaking it apart in atoms in the gas phase for formation it's using the elements and the standard states which are different vendors that after reactions until you get the reaction you desire and usually to make things cancel out you have to turn released 1 reaction somewhere backward and if you reverse a chemical equation you just changing the initial and final state the other way round and therefore you have to to reverse the algebraic sign of the state function because it is a state function at the difference between the final an initial Heath Slocum the changes sign and finally keep in mind that mean bond and we are not going to be as accurate as using them and of formation heats of formation because of the
averages and we're making specific molecules if we know the specific molecules we've got there OK now than there was this bonus problem with I thought would be at the I
thought I played thought I was ball on the green about a foot away from the cup and all you do is happening in the morning .period but some of the dead is you said gee there's a ball on the green I think what I'll do is I'll stick this wouldn't stick in the ground with the ball on it so I can really whack at an altitude headed off into the woods somewhere and you can still actually completed all that way but the problem is it takes a lot longer In this problem we didn't give the temperature because the temperature doesn't matter that was supposed to be at hand we recall :colon here's what we have we have these guys and that this a series of flats we have are and this is 1 version argon 1 liter 1 atmosphere here it is 1 later half an atmosphere here it is and any on to the leader's 1 atmosphere and of course we assume they don't react these noble gasses they're going to react but you have to be careful if you have real chemicals serious react that's a nightmare because then the temperature will change for Ashura and the number of malls will change for Ashura USC very careful but there was nothing like that here and what the question asked about it was a partial pressure in each category and the total pressure after the stock dropped to about all and at 1st blush this looks a little bit trick but here's the thing you just look at the gas on its own and pretend had the other ones aren't you just pretend they aren't there because in terms of the helium they there the ideal gasses the particles have no side the terms of the Argonne here when I open it this is a vacuum
and so is that In the Argonne just spreads out through the whole thing well I know he Andy here and looks like the change to 4 times so I know don't end of story and takes 1 2nd let's do it we
don't need to know the temperature each gas is independent of the others and we're assuming their ideal but that's safe and none of them have been any excluded volumes were assuming the volume of the Adams 0 but all we do is just use Boyle's law for each guest separately we figure the pressure and then have the pressures to get the total therefore for each individual gas it's as simple as the 1 the 1 equals the 2 I need to know what the 1 the 1 is but that's written on the diagram and I don't be
too this 4 times the wants the Argonne starts at 1 atmosphere and 1 leader it ends up in a total of 4 leaders of the Argonne and . 2 5 atmosphere the helium starts out in 1 later and . 5 and it divides by for the partial pressure feeling in this . 1 2 5 this and the neon starts out 2 leaders 1 atmosphere goes to foreign leaders therefore it ends up as passionate I had to get the total half and quarter and a
780 4 . 8 7 5 and very very quick I think I've got that on a slide that I'll get the slides in order for when they're posted on the
video OK there was another 1 here tell of osmotic pressure we had some strontium nitrate and imaginary pollutant from a farm the nitrates probably not imaginary but I don't think anybody's putting strontium on the cross he here is that strontium nitrate written like this at all dissolves we get 1 strontium ions and we get to 98 I am an I wouldn't want strontium cattle into nitrate and iron and therefore we get 3 moles of particles for this problem we take them all areas that were given .period Vermont going away whatever it was we multiplied by 3 because I is equal to 3 for this problem and then we use the pressures that is the most polluted times our the he was 300
Calvin and then we get the answer minutes again is quite quick and now I have slide that was out of order With the answers here but I'll get it in the right order for the video this is exactly what I said and this is the total pressure . 7 5 OK but I hope we can see that this wasn't as hard as it might seem on the
day but let's get back to free energy to recall the 2nd law of thermodynamics a survey but for any spontaneous process in an isolated system the entropy change is non-negative at equilibrium the entropy changes 0 but that's a special case or if we do a reversible if we do a reversible reaction then dealt 0 that's why it's reversible if we don't make any kind of additional entropy and the surroundings on the system then we can go backwards because in a certain sense entropy changes chart which ways forward in time since energy is conserved we can't look at energies and decide which way we're going forward but if I see a film that's running backward it's very easy for me to tell it's running back because there's somebody at the bottom of the pool there are and suddenly there's only swirls the water and the water picks them up in the air and back on the diving board and I say this film's running backwards I've never seen that happen the water spontaneously in a pool possesses massive fluctuations rose me out obviously the water has enough energy to do that but because the water molecules are not working together they can't do it on their own they can't just suddenly decided that her only out of the pool yes there's some chance miners 130 if that would happen sometimes but it's not large enough that
I'm never going to see it in the lifetime of the universe and so if I see something like that I can tell immediately if the film's running backward by the way things are happening what you're sensing is that it's very unnatural for entropy the decree and when you see that it is automatically assume that the film's running backward it therefore it's really entropy but we wanna watch out for for when we burn and create he the generate power or do other things what's happening is that we're creating entropy energies concerned were turning chemical energy into heat but he is much less useful than chemical energy increasing the entropy of the universe and when we do that we can't go back and well in every actual case the total change is irreversible because reversible it's kind of a kind of a special case for us to think about really reactions are irreversible quite as
entropy and it just increases because it's the most likely outcome and Adams don't have brain it's the same reason that if you throw to die you get 7 a lot more often than you get to it doesn't mean the dice are loaded the dice to try and do anything you just throw and it turns out there's many more ways to make 7 1 6 2 1 5 3 and 4 then there are to make to you better have both guys come up 1 in 1 you got sick and you just lost your back where they both come out 6 you box guards you lost your back it's not very likely but that does happen sometimes but if I have tended the 23 and I just throw the ball there's going be a certain range of
numbers but it's going to be very likely that I think that it's going to be very unlikely that all 10 of the 23 that I cannot 1 that's extremely unlikely and therefore we talk about large numbers of particles over commonly probable that the entropy is going to increase and that's because molecular motion is random just like the and therefore entropy is going to increase the most likely state there's no rhyme or reason it's
just probability In fact Boltzmann expressed terms of the probability but particular microstate could arise and so on this is in the book but this we talked about this when we were looking at molecules dissolving it's all gas molecules on 1 side of a two-sided container that's like throwing snake eyes over and over I would have very low entropy that's where he start on the valves closed because you've got trapped alleging opening and they can decide what to do on their own they're never going to go back to 1 side when you've got large numbers of particles never going to happen whatever he did there is irreversible when you open a tank of gas and let get out that's it it's out on the other hand equally distributed Rosselli would have a very high interest and on Boltzmann tombstone His is famous formula that entropy it is proportional to the natural law laws there's a reason why next large margins the thing itself of the number of ways that you can actually make a mistake you can just think of W as the number of ways if you take a course in statistical mechanics that you'll see this
formula or if you look at professor bias of license plate you'll see this formula as well OK
the university whatever it is this is an isolated system because 1 with the universe is nothing outside not around and therefore for any spontaneous process In this universe the entropy change in the universe is greater than 0 this during nuclear fusion and creating heat and sealing off all the solar winds and everything else it is creating huge amounts of but when we're talking about the lab we aren't interested in the universe were interested in our system and therefore we focus on what we're doing our chemical reactions In a flask and everything else everything else that he the stirring bar everything else is the surrounding and we we focus on the system because that's what we want to started we don't try to study the whole universe is too big In fact this is what all living organisms do they create entropy and the surrounding so that they can order themselves if you look at your own physical being where do you think the lowest entered the gates In your brain highly orders on no way that you can take gas molecules and best defenders and get a human brain In order to keep that going with burns about 15 watts continuously we
chucked out the were hot for producing heat all the time and we're eating all kinds of fuel In were burning it up they were producing gasses C O 2 comes out in our and so forth and if we don't have a source of energy we've got analysts as a society if we don't have a source of energy we got we just equilibrium on problem we have to have a source of energy we have to have some way to pull their tractors through the field we have to have somebody for ourselves and so forth and that's because the only way we can survive this by creating more interest in the environment for the more things you have the more energy you you go through the morning you create that's the way it has to be it's not no way around that whatsoever
Delta has recalled it's just a measure of how much extra chaos were created and therefore and I think I gave you the analogy that in a library of you said a loud sound everybody notices because it's so quiet in the library and likewise if I have a very audit system at low temperatures and I'm reject heat it does a lot of damage the have goes up like crazy but if I have a very disorders system that's already chaotic at high temperatures and I'm jacked the little heat it doesn't do much additional disorder and therefore the change readers low and so we have to take a ratio of the heat that we the temperature that already exists that's the measure of the entrance and to be careful we have to add that he reversible because he itself members not a state function so I can't say I had some heat I need to specify the path so that he is accountable and reversible is the nicest that so I think he had a constant temperature and I can't figure in the interview that I created otherwise it is much harder and an XO make reaction the reason most excellent there make reaction are favorable like our metabolism and burning fuel whatever is that they disorder the surrounding because we had a positive he to the surroundings divided by the temperature Of the surrounding In the positive he we add to the surroundings is a constant pressure is just dealt dates of the surroundings and that had to come from somewhere so that minus delved into the therefore when Delta H itself is negative
-minus Delta which is positive and the entropy of the surroundings is positive yet the of the surroundings has increased that broadly
speaking wide of reactions were favorable and then recalled that this is how we derive while we are interested in Delton cheap we don't want to take into account the the surroundings at all so we divide the universe into this surroundings in the system and Delta aid to the surroundings we substitute minus Delta sorry dealt s of the surroundings we substitute minus Delta aged over tea that's the entropy we created by an overreaction added subtracted from the surroundings whatever happened the system did the system itself become more ordered and disordered we multiplied through the whole thing by T minus t we get there since Delta Hess of the universe is greater than 0 that means the minus the Delta Hess of the universe is less than 0 and that means that this thing which is the same Is Less Than Zero and because this thing occurs so often we give it a special symbol delta G 2 0 at constant temperature and pressure delta G decreases things roll down here she goes lower and lower and lower until goes to the lowest part and that's it forever therefore we can say for any spontaneous process at a constant
temperature and pressure the free energy decreases so
we write delta G dealt a major mines he dealt best and we forget about putting surroundings and system because there's always means the system we the whole point out youth we don't take into account the surroundings at all a reaction that don't seed into the surroundings this favorable has as a big negative Delta age got a big negative number yeah looks like Delta T is going to be negative if in addition to dumping heat into the surrounding the system becomes more disorder for example I producing gas from a solid that's going to be wildly favorable that's why burning chapel would is wildly favorable because I produce heat into the surrounding and produce C O 2 and stuff from the wood from a solid I turn it into a gas see you later often go disorder increases like crazy that reaction is very very favorable In humans figure that out that's why what we do mostly we Bernstein stuff because that works this kind of reaction there that is excellent Thurmond and disorders the system will be spontaneous at all
temperatures but that doesn't mean that it will be facts it just means that it's eventually going to happen but if I leave Chumpol would eventually it's going alternative C O 2 and 2 0 it's not going to help me much if I don't actually light it on fire because happened to slow but if I look at all books I noticed that the pages of turning yellow the sort of looking like when I'm in the oven they're burning it is burning up very very slowly and if I leave a very long time the history of Act it's going to be a very long time that's why preserving old manuscripts is tricky because they can be very fragile and and they've been oxidized over time the only way I can stop that inspired story manuscript in an atmosphere of the that nitrogen then oxygen that I'd say unsafe because there's no oxygen than the reaction contact since combustion requires oxygen so I could do that
if I got a reaction that absorbs heat from the surrounding reaction that when I run it gets cold the he from the surrounding it has a positive dealt age and that policy Delta age means that Delta's she is going to be positive unless something else makes it magnet if the system becomes more disordered dealt age sorry dealt a test is positive and that means that minus the Delta S is still negative and so it's a it's a tug of war between Delta 88 which is positive and minus the velvet dress which is negative and that means that if I make seem big enough it's going to happen that means that any reaction that absorbs heat and the system becomes more disorders will be favorable at high enough temperatures and the example that I gave you was dissolving ammonium nitrate in water he gets cold but it still happen and this reasons is part of the reason why your clothes usually get cleaner refuse warmer hot water the wash them in because the kinds of things you can dissolved don't want actually dissolve there could be an end of term process try to guess loyally gown pocket close to going to solution in water the water making all these hydrogen bonds and saying no to keep out the and so to overcome that you read about and even hotter and hotter water
sometimes it works better just depends on what the material is what the reaction is himself or so forth for blood you don't want to put it in hot water because then that sets the proteins like frying and then the stain never comes out of fear of blot on something you watch Cold War very gently forget and you don't just jump in very hot water because then the sustained settlements it turns brown and the pretty much OK enough we have
reaction the dumps into the surrounding but the system becomes more water and minus the Delta as positive an example of this is by Parliament chemical equation but a phase 2 when I have water freezes on it dumps he into the surrounding people find confusing because they're saying well you're making ice isn't getting cold the way think about it is that if I have a chunk of ice and I want melted in the water at the same temperature do I have to put in energy the answer is yes I have to put in energy to melt the ice therefore when the water freezes that same energy comes out into the surrounding bank In this case the reaction will be spontaneous at low enough temperatures and of course we know but I saw only freezes at low enough temperatures at the temperatures not low enough the ice doesn't free when oftentimes if you've got citrus crops and you're worried about a hard freeze if you've got water use predatory With a tunnel water because there are a lot of of the cold air will waste its time freezing the ice and it will free the eyes 1st before it gets any colder and hopefully by the end of the on and you have frozen the lead solid and see until
the plant killed your harvest for the year solids always form loan of temperatures because they're the most ordered form of matter With the lowest it should be a weekend makes solids form just by cooling things down lower and lower and lower wheat a solid nitrogen for example of we want by cooling it enough finesse this principle here we just lower the temperature until it's terrible if we are
finally a reaction that absorbs heat from the surroundings and has a positive dealt a and the system becomes more water that's a non-starter this kind of reaction will be spontaneous at any temperature but we cannot do a reaction like this and let it happen by itself if we have some kind of chemical equilibrium but has this this characteristic that the system's becoming more water and it also has a positive dealt age that means if we try to run a reaction like this with a positive delta G we are going to get much prime were always going to have this kind reacted in a little product what can a stew In that case is the couple the reaction they want to run with another reactions that's why only favorable like burning coal I can't make any reaction run the I can electrolytes water
with electricity and produce a student 2 or whatever I wanted to run things backward as long as that of power of In the power supplies plugged into the wall and the wall somewhere as "quotation mark plugged into a power plant and a power plant I assure you is running a wildly favorable chemical reaction to generate power of sometime this burning natural gas oil coal nuclear you name it it's doing something like that and together thanks to the power plant and what I'm doing the overall delta genes negative and so I can synthesize very complicated molecules very highly ordered of things by extending enough energy and that's exactly what we do when you grow up and develop From the salvage sitting there and dividing and turn into you that takes a lot of energy to figure out how much you eat over all those years executives that center it's a lot and all that's wildly favorable because the metabolite reduce CO to and then your body takes things and intricately made gigantic molecules that are very unlikely to occur spontaneously but they can only happen as long as you find something to eat they won't happen if you don't they're cannot OK Wilson will stop there and will pick this up next time this issue
Computer animation
Computer animation
Computer animation
Computer animation
Computer animation
Computer animation
Computer animation
Computer animation
Computer animation
Computer animation
Computer animation
Computer animation
Computer animation
Computer animation
Computer animation
Computer animation
Computer animation
Computer animation
Computer animation
Computer animation
Computer animation
Computer animation
Computer animation
Computer animation
Computer animation
Computer animation


  724 ms - page object


AV-Portal 3.8.0 (dec2fe8b0ce2e718d55d6f23ab68f0b2424a1f3f)