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Lec. 16. Equilibrium Constants: Temperature and Pressure
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Title  Lec. 16. Equilibrium Constants: Temperature and Pressure 
Title of Series  Chemistry 1B: General Chemistry 
Part Number  16 
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 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  10.5446/19466 
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 16. General Chemistry Intermolecular Forces  Equilibrium Constants  Termparature and Pressure 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. 
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00:19
workers that the world is coming to an end this year so I guess all our problems are over notice how easy it is when the world coming to an end and forget about longterm planning the party on of course all of our world to come to an end and sometimes unpredictable so it's kind of important from time to time to imagine what you would do if you're going to die today who would you call what grudges you drop quality stadia parents your friends anybody who 7 influence on your life and then my advice would be going out and say some of that you know you don't think you're going to die there's no point in waiting many people wait too too long and then the other person dies and never get a chance to tell them how much you appreciate something they because you kept putting it off but put things off forever we all have a shelf life unfortunately where thermodynamic we unstable and that means we're doomed although hopefully not too quickly but eventually we argue but for now let's imagine we're going to live long enough to take the the final yet grade that type of thing and so will be a good idea to plant them in with that in mind let's get on with things talk about the equilibrium constants or pick up where I left off all but the from up again and we were actually trying to figure out if we knew the equilibrium constant for the synthesis of ammonia at room temperature based on the tables could we figure out what the yield would be that some higher temperature where we have to run the reaction and the answer is we can do that for sure but we have to make some approximations unless we make some measurements but here's what we have we have dealt
03:27
formation of ammonia His minus 16 . 6 killer jewels from all negative what would what would you say it's somebody I came to you and said I found something interesting in the table here is a molecule that has of positive delta G of formation most of them are negative but there are few in the table Hungarian example hydrazine and 2 H for metal hydrazine I think is used in rocket fuel some if you're given that information what would you say since the molecule exist anybody got any ideas I'll tell you what I would say number 1 although hydrazine has nitrogen and hydrogen like ammonia I can't make hydrazine in high yield From nitrogen and hydrogen because it as a positive development she thought as a tiny I could probably make a little bit Bernama seconds hydrazine must be kinetically stable like a human being hydrazine must be doomed eventually default part at least into hydrogen and because it's unstable with respect to the elements that was made from the gonna fall downhill eventually and if anything like that usually you want handle extremely carefully those are a lot of things like explosives I have a big delta and then boom when they detonate you get them going to products with a lot of energy but ammonia doesn't have that problem and we have figured out but about the future the balanced reaction for 1 mole of ammonia because Delta G refers to 1 mole of ammonia is onehalf molecular nitrogen plus 3 outs molecular hydrogen gives 1 wall ammonia if I double our reaction 5 double delta G that's very important when Delta G formation is listed it's if I make 2 models of ammonia Delta duties twice as big this life 2 kilograms of ammonium is twice the mass of 1 kilogram of ammonia tilted G behaves that way and we have a formation "quotation mark excuse me in equations the relates taped adult G and their and so we just put in the numbers and we make sure we have the the right units now we get it is easy to the plot 6 . 5 9 6 3
07:05
and that's about 730 that's favorable and these were going to get mostly ammonia not the
07:17
other temperature we need to make some assumptions 1st we have to make the assumption because we don't know the heat capacities of the products are reacting that Delta agent Delta are still dependent themselves too much on temperature the entropy is different than the and because there's no entropy of formation the entropy is a reference to absolute 0 temperature and any kind of molecules or atoms at finite temperature has some disorder it's moving stumbling around energy is distributed in the molecule in different ways and be searching entities than randomized to the maximum extent possible because that's simply the most likely effect that's going to happen if we use are equations for the state function of delta G Delta G was Delta age minus the dolphin S and the relationship between log of care and Dalton G we can set this up into different temperatures and then find the value of lot case of the 2nd temperature if we know the value of logic at the 1st temperature and that's
08:44
how we have to do it from here we go for 4 at each
08:52
temperature I'm going to write log and I'm gonna put in parentheses the temperature I'm calling it just to keep track so loggers K at temperature T 1 His equal the minus delta G standard the temperature T 1 over are the 1 and then I'm gonna put and Delta age In Delta I'm going to do the same thing for temperature T 2 except I'm gonna put in and then since these bases equal the best and this is equal to the best then log K locate the 1 minus located is equal to the righthand side here minus the other righthand side and I've written that all out there's a lot of today and temperature T 1 minus located temperature T 2 factored out ,comma minus 1 overall Delta H T 1 over T1 lines Delta agility to is a set minus of here 1 over once dealt as the 1 minus 22 and now we have to make an assumption the assumption we make is that Delta agent don't ask themselves don't depend much on temperature as we know that's not quite true but we're going to assume it's true because we don't know the heat capacity we assume Delta Agent T 1 is equal to Delta 2 more just call adult age in the same for Delta then conveniently because this Delta hasn't missed out are the same this term goes away and so we have the natural logs today the temperature T 1 minus natural log K temperature T 2 is now equal to minus Delta H over our times won over T1 minus 1 over 32 this not surprisingly is very very similar the classiest "quotation mark Pyron equation the only difference is that we have the vapor pressure well it turns out that if I have an
11:16
equilibrium between pure liquid and vapor assessor and some pressure the equilibrium constant use just the vapor pressure of it classes Pyron equations the special case of this more powerful equations and then because I'm subtracting the lots I can tidy this summer and say the natural log of K at temperature T 1 divided by temperature heat to the natural order the whole thing is equal to this and therefore what I need to know in addition to Delton G 1 temperatures so I can get lost there is I needed Delta H for the reaction and some temperature enough I assume that depend on temperature than to 298 will do so I look bad and by
12:11
recalled the Delta H of formation for ammonia for 1 mall is minors 46 thousand 300 sets of jewels from all but put that in a lot of K temperature T 1 provided OK at the 2 minus 46 300 over are in jewels won over 298 minus 1 over 598 I put the . 1 5 but I didn't want that this drop line because it makes it hard to read that didn't fit and not on making tiny because it's hard to read but when I did the calculation with 298 . 1 5 and I find that lot of exterior temperature 1 divided by the is equal to plus 9 . 3 6 7 21 was 298 because I'm keeping things in order well we know what a temperature T 1 it's OK at temperature T 1 divided by temperature T 2 the exponential function of the Lord is just the thing In the exponential function of this plus minus Q the plus 9 . 3 6 7 unifies all that using Taylor 51 at 7 30 I get Taylor 52 is equal to 7 30 times the to the minors 9 .period 3 6 7 and so I get 6 . 2 4 times 10 to the minus 2 so you can see that my yield went from wildly favorable 730 2 6 per cent for prepare by
14:12
cranking the temperature that's how a lot of things work and that's why the cranking the temperature up on the planet just a little bit can shift the equilibrium concentrations of things like a giant teeter totter With unimaginable consequences we can imagine them but we wouldn't want to live through them necessarily it's not just that it'll be hot it'll be totally different too and sometimes you don't know all the equilibrium going on in the ocean so you get surprise OK at the
15:04
highest future it's less favorable shortly we go up to 798 that's where there run remember about 500 Celsius that we find With Delta H minus 46 thousand 300 jewels from all we do the same thing and now we find that what they at the 1 divided by the who is equal to the lost 11 . 7 and the bad thing is that it's an exponential function and so now when I multiply 730 but needed the miners 11 . 7 I less than a percentage at 6 . 0 5 times 10 to the minus 3 L I'll just remark here that the assumption that we've made the delta H and Delta s themselves don't change much with temperature is not going to be accurate when you change the temperature hundreds and hundreds of degrees or a thousand agree that's too far off that assumption to be any good but if you change your reaction from 25 Celsius to 35 Celsius that's probably going to be a very good assumptions and sometimes it here in the lab and your optimizing reaction
16:34
if you just eat it or just cool it a little bit more use a different solvent that has a higher boiling point when you reflexes that you suddenly get much higher yields because of this exponential function you can go 50 per cent 99 per cent pretty pretty readily and that's just much much more useful then if you have a reaction but does that kind of thing OK some
17:02
observation the equilibrium constant depends on exponential function of the free energy therefore small differences in free energy lead to large changes in the equilibrium constants that's why for a lot of reactions if I see the delta it's something number of killer jewels from all the negative I can just pretty much assume 100 per cent yield because of this exponential function and likewise temperature because it's in the denominator of the exponential can shift the equilibrium greatly as we saw In the last problem now let's try to shift equilibrium back in our favor we were carrying missiles at a pressure of 1 atmosphere and we worked really asking how much money we got versus how much hydrogen we started with hydrogen is the most expensive reagent in the sentences nitrogen is pretty much free from the air I will do it with respect to the hydrogen but 1st let's just look at this that this shifting the let's just take a hypothetical reaction is in equilibrium with the but a and B have different free energy the question is what should the difference in free energy B To get 90 per cent yield of the what should be get 99 per cent yield and what should
18:42
it be to get 99 . 9 per cent a year which would be essentially considered quantitative and it turns out here it works in our favor so let's assume we
18:56
run the reaction at to 98 analyst just state Delta G of this reaction Lagos to be bludgeoned to 98 and figure out what we need well we wanna get 90 per cent of the at equilibrium and that means we have 10 per cent of a and so . 9 over .period 1 is not that's is not and therefore if we take the the natural log both of above if we solve this excuse yeah we take a natural log and solve this for Delta G we get delta G for the reaction should be minus RT log Case 9 we put an and jewels we put into 98 . 1 5 television and we put in a lot of 9 and we find that we only need minus 5 . 4 5 killer tools for mall which is hardly anything for 99 per cent yield the only difference now is we have 99 per cent of the at equilibrium and that means we have 1 per cent of a left over the . 9 9 over .period 0 1 is 99 a lot of 99 it is fortunately by the way lots work they never get that big even if the numbers of we get delta G for this case is minus RT log 99 it only goes to minus 11 . 3 9 killer jewels from it's not it's just twice and for 99 . 9 the at equilibriums . 9 9 9 it equilibriums . 0 0 once OK is 999 but again lot 999 doesn't get that big when I multiplied by minus I get negative 17 . 1 2 those jewels from all for a typical reactions that you're likely
21:13
to cancel out but involved the burning of hydrocarbon that getting C O 2 inmates to all dealt interviewed for that reaction is going to be used and negative and so we can pretty much consider that there's nothing left if there is in fact the materials here what's usually last when you burn tons and tons of stuff is the small impurities that are written in your chemical equations sulfur mercury cadmium and other things that don't burn uranium thorium radon other things and all those come out In the fly ashes you burn coal and if you want overnight cleanly then you have to figure out what you can do with all those things for the longest time we did care we let all the mercury in the fly ash flow into the ocean and that's why the fish may have higher mercury content now I think fish always have some mercury content but I don't think we call that much OK now let's go back to
22:27
the Harbor process and let's try to squeeze the prime were forced the heated up would force the heated up feeling OK it's small but we are forced to run an atmosphere pressure and because there's more moles of gas in the reactants then there are the products I made a comment without saying why but we could put pressure on it and forced the reactants to go over to now we're going to do a calculation to show how that actually works let's take our same reaction and let's figure out what the equilibrium constant state is in terms of partial pressure the reason I'm using Kate because all these are gasses and that's the natural thing to you and even tho the non integer story geometric coefficients when I write equilibrium constants I always raise the concentration the story convention power if it's 1 have and the square of the concentration of history have it's a concentration of the 3 absence so for its whatever the actual number is it doesn't matter if it's not integer and
23:55
of course not integer powers don't scare us anymore because we are not going to ever tried to solve the equation analytically we're just going to guess the answer and we're so they're guessing by this point we're going to get it right let's have a look this looks a little
24:17
bit messy people will go through it step by step by step take the definition of KP its products partial pressure of products divided by the standard profit because Haiti has no union divided by she the partial pressure of hydrogen divided by the standard pressure raced to to the 3 have power because it had a 3 have some chemical equations multiplied by the partial pressure of nitrogen divided by the standard Race to the onehalf cup and then I can use Dalton's long Dalton's losses the partial pressure of an ideal gas it is equal to the mole fraction times the total pressure and here I am using To be the total pressure therefore follow ,comma diagrams and says he His 300 atmosphere and that's the he I'm gonna put in there the total pressure and likewise I can do the same thing here mole fraction of hydrogen times the total pressure and the mole fraction of nitrogen fracture raised to the power and then I'm going to pull out the mole fractions and separated out the mole fraction part From the people now I've got this leading term which is all the more fractions which is going to be what I'm going to call the yield and then I've got all these pressure terms which I don't care so much about but it seems like the winds blowing from behind because pressure to the 3 halves times pressure to the onehalf I the expo ancestors pressures squared but he over P. not here on the bottom of the Over P. not come simplify that I and with the knocked over he now we can sort of see how it works when we change the pressure Craig doesn't change because
26:37
scrapie it is related to delta G standard and delta G standard is that the standard preferably 1 atmosphere therefore when I change the pressure take me doesn't change when I change the temperature take the does check both things can change that but here's the thing if
27:05
take he doesn't change was suppose got our miserable yielded . 6 per cent year over and now I cranked this guy and this guy was once before but I cried he the some huge number like 300 but this has now won over 300 well that means that this thing here with the axes traffic get bigger because he made this term here get smaller and the only way this guy can get bigger is if the mole fraction of ammonia increases like crazy but that's what I just said is that because I more gasses as reacted by squeeze down on I'm going to much more product so these guys will go down and this guy will go up and the harder I push on it the higher yield I guess why don't I just push on it too thank and fears the answer is that costs too much money because if I want to squeeze that hard I've gotta make a chemical plant world title that thing so they can take the pressure and that cost me a ton of money and therefore it's more economical for me to recycle the reactants that I can't quite get into products lead off the ammonia by condensing and cooling its system and then just go around again at the same price that's going to be more economical than trying to run 1 reaction and get to go all the way and that's just the economics of designing a plan and economics are important because if the fertilizer cost 10 times as much because I'm doing something in a crazy way then I can afford it OK the last actually do this calculation this there's is going to be very long society the Silopi you can follow it but will do it step by step by step here is the problem what pressure would take at 598 the intermediate temperature to boost the yield of ammonia compared to the residual hydrogen by a hundred times compared whatever yield we had we got and that the pressure of prompt 54 we calculated but we didn't calculate the equilibrium concentration and we have to assume but the reaction reaches equilibrium in in a real chemical process people don't really care if it reaches equilibrium they despair of get a pretty good deal of proper especially if they're going to recycle the reactor and let's assume that we start with a 1 2 3 nitrogen the dash ratio the story geometric racial for ammonia battle to simplify Our calculations but of course again when you're running a plan you may not but that conditions and you may actually try to game the system a little bit by putting in much more concentration of something that's the cheaper reagent to drive the equilibrium it is the right decision actually used much more nitrogen and hydrogen as you go to try to convert all the hydrogen Over 2 ammonia I don't actually know how they do it in practice OK let's 1st figure out what the ratio of the mole fractions ammonia the hydrogen would be at 1 atmosphere that's going to take us a little but a calculation and the next let's increased whatever this ratio turns out to be by a factor of 100 and then figure out what he not over he should be he knocks 1 atmosphere so that will tell us what he should be In atmosphere we're
31:12
talking to a chemical engineer we may converted PSI so they know they may have things in terms of how the inch because that's how lot of things "quotation mark we have to proceed step by step we use the partial pressures than
31:30
Dalton's long and to convert a mole fractions and we have to be careful to include the powers of 3 deaths and 1 onehalf of just written that here so we can see it again we have today at 598 that from before and after everything drops out we have the mole fraction of ammonia in the numerator and in the denominator we have the mole fraction of nitrogen the 1 has power and the mole fraction of hydrogen to the 3 halves power and then we have this term left over I the standard over the if we had the same number of malls of gas on both sides this spring state but the powers of
32:18
the we are going to be the same on the top and bottom and in that case if you have the same number of moles of gas on both sides squeezing won't do anything much will won't change and so therefore you don't squeeze under those conditions were lucky there were taking more moles of gas when we make ammonia because that gives us a lever the push on and
32:49
let's for the sake of arguments start with 1 half time some number it turns out it won't matter what it is but I'll call and not let's start with 1 half and not moles of nitrogen and we have 3 times as much hydrogen therefore we have 3 outs and not moles of hydrogen initially before we actually conduct the reaction we have no an age 3 this is our initial conditions the number of moles of nitrogen starting out this 3 has and not the number of moles of hydrogen is 1 half an hour and the number of moles of ammonia is 0 and now we let a fraction outside of the reactants react and for some reason which I don't actually know myself whatever chemists deal with gasses the fraction of reactors Alpha and whenever they deal with solutions the malaria season reactors suspects but anyway it doesn't matter what you call it it's an unknown and we're going to try to solve the fraction that this product based on the values case and very very messy equation which would intimidate everybody if they thought they had to solve exactly because it could be potentially quite different as to quite difficult to solve now this fraction is on number were going to try to get it has no units and it's between 0 0 and 1 itself 1 then all of it reacts to ammonia that's 100 per cent yield it offers 0 that's what we started with here that's what I've written whenever I set up an equation like this I always put in alpha or acts or whatever it is the range it could be because I want to know where I should get the chemistry all these things are positive numbers and they are imaginary numbers or anything else funding and that helps you a lot of the guests in 2 dimensions it gets very very much part today you may need a computer to do that and I see that it all works out it makes sense 1 office equal to 1 there's no reactants leftover it's all products 1 of the 0 there's no products it's all reactants and I see that they're going away in the right way and that's because I put the 3 outs onehalf here and not some crazy things here by multiply that by
35:42
3 have which is a very very confusing said strategy the let's
35:50
figure out the partial pressure but let's figure out the mole fraction so we can get the partial pressure the figure out the mole fraction we have to add up the total number of moles of reactants and we now know if a fraction of a reacts how many moles of nitrogen hydrogen and the 1 we've got let's we have the number of moles of nitrogen plus the number emulsified plus the number most of ammonia that 3 halves and the 1 have at up to 2 the 1 Southall was in both of these guys so I get to times quantity 1 itself at times and on and this guy here was Alford times and on and if I expand this area to minus 2 off of post office so I get to minus Alpha plans and not that's the total number of moles 1 ounces 0 there's 2 moles because there's 3 have moles of hydrogen and onehalf mole of nitrogen when of 1 there is 1 small there's 1 so of ammonia but again I check but 0 1 and I made sure it makes sense that I haven't done some sort of logical heir in setting it up and then I've got this equation here for the total number of malls the mole fraction is just the number of moles of each of these guys divided by the total number of moles and ideas very patiently work it out I don't for a short cut it and for the mole fraction of nitrogen I get 3 halves the fans 1 mind itself at times an hour divided by 2 minor also Trenton Ont NEC and not goes away it doesn't matter because we're talking mole fractions but it has to go away and therefore the mole
37:56
fraction of nitrogen is 3 halves times 1 minor itself divided by 2 months and I don't sweat about that and forget this .period just leave it like that that I move on 2 hydrogen sorry I'll fix this this was meant to be hydrogen because hydrogen has the 3 all 6 this 1 before I close this line this is meant to be the mole fraction of hydrogen on site and likewise this 1 is also backwards but fortunately it won't matter since the mall was for arrest of the calculations of and for
38:53
hydrogen which should have a 3 hours instead of a onehalf but is basically the same thing we get a number and we get 1 line itself cited by 2 mine itself and then the mole fraction of ammonia is again the number of moles of ammonia divided by the total and both of them depend on how structural far the reaction goes the top part itself and not the bottom part is to myself at times and not the I Ralph over to and the thing I want to emphasize that this is a very simple reaction and yet I could potentially to the city's power here soul and that's why I don't advise trying to solve things analytically there is a formula for a quite dramatic for the route expire policy Act policy there's a formula there's a formula for acute it's pretty bad there is a formula for a quarter the text of the 4th was the excuse of the history of the that formulas 28 pages long there's been here before Route X 1 equals Barajas Davies the greatest all the power and an amazingly when the equation it was shown by a long time ago that there is is no formula for a general went equation it's not that we can't figure it out it's that it doesn't
40:44
exist In terms of raising thanks to a power multiplying things adding subtracting and dividing and those of the weapons we have in arithmetic the fact that suddenly at 5 becomes different is very mysterious mathematician and fascinated and as you go beyond 5 none of them have formula that you can write down but you can always guess the answer for the 1 you want and we don't want all the funny routes the negative an imaginary we just want the positive real number that's the pressure or mole fraction Of the gaps so we don't have to be intimidated by the end of this remark here mole fractions don't depend on and not just before but if your mole fraction depends on and not he did something wrong I usually put an audience because I like to see it go away but a shortcut is to just say and not 1 and leave it out it's a little risky because if you make an arithmetical mistakes you won't catch OK now let's
42:02
substitute in those horrible things for the mole fractions we get this my goodness gigantic equation at the start of the quarter this would have been so intended Madeleine by giving me there was no explanation that followed her out of the conference and we .period came back he looked remember profit apartment but now this is a great thing because you know all the clean 0 online and you're going to get the answer show you how to get the answer very quickly doesn't matter how intimidating it is because they're all the same we don't care if we can write down the exact solutions now the 1st thing here is that when you've got fractions With infractions they are extremely confusing and prone to error you have to be very careful if if I write 3 line for a line saying side 5 I don't know whether I mean 3 sets threefourths divided by 5 4 3 provided by 4 450 and unlike multiplication division is not associated I have to know the order but I'm doing the operation and therefore you have to get used to writing great big lines here and tiny ones here indicate which is done 1st and I liked but these things embraces the sale of this 1st before you do and I do not keep these things in here for a very long I write it down and then the fastest thing I do is try to get rid of it and the way I get rid of it is never by dividing the way because division is prone to error for the reasons I just said I get rid of it by by multiplying like crazy by stuff until I clear out all the jumped out of the stable so I have to find some way to clear things out especially denominators in the denominator I don't like on going focus on denominators and the denominator and in it's clear those guys out there
44:46
as fast as I can by multiplying by the appropriate thing and if the talk gets messy so be it we're here let's clear
44:59
out to minus office where and let's clear out the numbers here's what we have originally I've just tidied up a bit 3 has to the 3 outs 1 after the 1 and 1 minus offered over to myself over to the 3 outs plus onehalf which is squares I see this thing down here I multiply the top and the bottom but to myself a square to get rid of this guy I see these numbers here with fractions and I'm I don't like them I'm all by the top and the bottom by 2 the onehalf Interstate turned upside down and keep the power and I multiply the top and the bottom by twothirds the 3 hats that clears out this this and that and finally I can simplify my resolve I get a lot of spinach on the front squared twothirds to the 3 power and I of the offer here I had to minus figures on and multiplied by 2 mines office where I pick up a 2 minus the other steps down the bottom I have 1 itself upon the square and then I have my he knocked over this is not so bad but this is not so easy either my goal now is given a value of the the sulfur also assuming that he is equal to standard In other words all for the mole fraction of ammonia
46:42
purposes hydrogen at 1 atmosphere pressure and 598 . 1 5 dollars and I go straight to putting in the numbers . 7
46:56
6 7 0 . 7 6 9 8 is a square to 2 times 2 thirds the 3 outs power case he added 598 was . 0 6 2 4 near enough he is equal to the standard so that 1 and now I have an equation without often in on a target hit that doesn't depend on Alpha and that's the conditions for guessing and furthermore I have arranged on Alpha between 0 and 1 if I know nothing at all I can play a game of cotton and have guessed . 5 of its 2 bridges . 2 5 and then subdivided they go by the method you don't have to actually do it that way because they're faster ways to get the let's look when Alpha is 0 this whole side so how equals 0 is too small 1 Alpha is equal to 1 Ford near 1 this thing blows up was huge number because 100 per cent yield mainstays infinity and is nowhere near insanity previous small so I know what else is going to be small and based on that
48:21
yeah I'm gonna go go ahead and get some values in the office and if I don't know
48:28
anything I'm gonna put on 0 I get 0 my target values . 0 6 2 4 and I say that's too small now the question is what should I put in and 1 trade His if a small put in just try you know what number . 0 6 2 4 it's pretty small put it see what you get that's what I did I put in . 0 6 2 4 and out popped . 1 0 5 8 8 I don't believe all those digits but I'd like to write them down just to see what they are my target is still . 0 6 2 4 now it's too big now I went up by 0 2 . 6 1 at the function went up from 0 to . 1 therefore I'm going to get us something about halfway In here and this is what I did . 3 1 about half insurance this is . 0 5 now it's looking pretty good because now I can see how it's behaving I want . 0 6 2 4 now it's too small but now I can see about how much I need about this I forget this to go from point 0 5 2 . 0 6 and it's about 104 so that's what I guess and bingo I get . 0 6 5 for 9 a little too big I want .period 64 but now I'm very close and I've got to estimates here and so I can Xu man pretty well and I guess . 0 3 8 I get . 0 6 2 0 2 we'd be small and I have to estimates here I know it's between here and I know it's closer to this 1 and I guess . 0 3 8 2 and they go police 3 digits in it's on Monday quit here and say Look this is close enough the value of our office that's between 0 and 1 and it's real the solstice equation is . 0 3 8 2 I think that's really . 0 3 8 2 2 is even closer that's the value now we have to go back and figure out what the the ratio of the mole fraction of ammonia the hydrogen but we have that because we have a value of Alpha so we take
51:47
the ratio of those too and if we simplify it the mole fraction of ammonia itself over to my the mole fraction of hydrogen this might be a mistake again I'll fix it sorry what happened to be 3 halves times 1 might itself over to myself so instead of 2 I should have twothirds here twothirds of OK but let's let's just follow it through assuming we get this if I put in the value I got then a ratio of the product the major expensive reactor His .period 4 0 7 9 4 8 I doubt about they per cent yield based on how much hydrogen I use now if I want to increase the yield this is actually with respect and Nike I think so worst with respect to hydrogen anyway to increase the ratio by a hundred we just say Well this we want this number instead of b . 0 7 we want to be 100 times bigger so this number the ratio should be 7 . 4 . 9 4 a this will be another number 1 I fix it and if you solve that it's easy to sulfur Ralph parents about . 8 did also let you figure out if if office .period 8 and you know Katie and you know the formula for it's simple to
53:45
figure out what the pressure should be and easily see that it'll be a couple of hundred atmospheres and that's exactly what they use so that explains exactly how they're thinking OK sorry for the confusion between nitrogen and hydrogen it was and I guess I knew I was going to be confused because
54:11
I said I personally find these capable he problem to be the ones that require the most care they're the easiest once to get wrong they're the toughest ones to figure out at the end up with a lot of fraction the equations that we have to solve Indiana if we've got a big reaction the equations are absolutely in they have things to all kinds of powers yes How don't copy down something wrong because help which slide this 1 this 1 and this is just the equation to solve offer this parts OK because luckily there juxtaposition cancels out but this is the numerical equations the sulfur I hope things will go back here on
55:56
but it doesn't matter how intimidating the equation is because you know between 0 and 1 so it's fairly easy to get guessing is the most efficient way as long as you only have to obtain 1 answer if you have to obtain things versus a variable you're going to have to that you don't want to be guessing over and over although if you don't change the pressure much your last gas is a pretty good estimates for the next year the emphatic creep along like a snake and your clothes and then you just the next value and you watch the yield go up as you turn the pressure out we know going get bigger and you just as a little bigger than music then on many comply if you've got a graphing calculator this is the the thing to do it is too graphic but don't grafted between 0 and 1 because usually at 1 blows up To infinity and new graphing calculator that shows you nothing because it gets too big and can't Scalet to fit on the display therefore I usually graphic between 10 per cent and 9 per cent it's not too late and if it's not in the range I need there and I assume here where I miss graphic from that range and that gives me an estimate of what value will hit the the target that I want get 4 cases the graphing calculator can help up speed things up a lot or if you have a spreadsheet obviously OK
57:38
equilibrium is dynamic and that means that even though Ed equilibrium the concentrations but reactants and products don't change that does not mean that the reactions have stopped they have not stopped they are continuing to and what it means Is that they're balancing out I've got to jugs of water and 1 reactions pumping water into 1 side no 1 reacted pumping water into the other side and they're canceling out so that level of water saying there but if I look in detail it's chaos things are moving around all over the place all the time because the reactions can still occur and they do nite of ammonia some of it goes backwards To make hydrogen and nitrogen and some nitrogen and hydrogen then goes forward if I take any chemical reactions and look at microscopically then it can certainly in principle run backwards because that conserves energy too there is no different and to assume even know we'd like to to assume that an unlikely reactions running backwards at this favored reactions never happened is too unlikely entropy steps in and says No no no that's too unlikely the unlikely then passed that happened sometime
59:28
you have to get hit by lightning occasionally that happens In fact if you look at how many lightning strikes there are planet all the time it's amazing that you haven't been there yet but cost people who entered a lottery don't seem to realize that the chance of winning the lottery is about a million times less than getting hit by lightning and yet they are worried about getting hit by lightning but they somehow think they're going to win the lottery they're humans have a bias for positive things if you give people bad news they say the 1st reaction is I don't think that's going to happen that's the natural human reaction if you give them good news and chance they say that I meant I can win I can fantasize what I'm going to do with the money to but then when you enter a play you lose of course because they don't build those giant casinos by losing a ton of money and in fact it's interesting psychologically if the study why people get addicted to gambling when you lose there is never any remark the machine doesn't say you last year going broke watch out its disquiet and then when you win even quarter the lingering being blamed and when you think back you only remember winning because those are the only memorable moments you talk to people who go to Las Vegas everybody wants nobody says usually I got cleaned out 1st of all make the same like a soccer nobody wants to actually broadcast but 2nd of all you may actually be missed remembering because you actually remember the big deal when you when they have that psychology figured out that's how they make money OK
1:01:44
let's talk quickly about homogeneous reactions it's a simple terms you can think of no they homogenized milk so that the cream doesn't separated out on the top and homogeneous means that its allinone fate like all gasses for a single solution if you've got a homogeneous equilibrium the reactions never go 100 per cent and the reason why they never go 100 per cent is that it turns out even if the product so wildly favorable it's always even more favorable to contaminate the product with a little bit of the reactor and the reasons why is that when you contaminated products With a little bit of reactants they get mix and mixing this entropic favorable the rather than being obscure thing which has to low entropy the products will spontaneously give a little better reacted so they can mix with them because they're all on 1 thing and then that turns out to be the most favorable outcome such sometimes of course there's hardly any reactants left of the reactions very very favorable but in principle there is always a little on the other hand if you have had a genius so you have more than 1 phase like a solid turning into a liquid phase transition or a gas reaction coming down on a solid surface then because there are 2 faces these reactions can go 100 per cent and the big differences the by the definition of phase faces don't matter and if there is
1:03:53
no chance mix them there is no penalty and making 100 per cent of the problem because you can't mix with the other guy anyway because he's a different fate then you are and therefore you can go 100 per cent all face of Type 1 phase transitions like so for example if the
1:04:17
temperature is above 0 Celsius and the pressures 1 atmosphere there is no why not present at equilibrium it's all liquid water because ice to water is ahead a genius reactions and if the temperatures below 0 and the pressures 1 atmosphere there is no liquid water present that equilibrium it's all right the same reason and likewise if we the temperature at exactly 0 we could have any amount of ice and water we can't say with the concentration in if we have the pressure exactly the vapor pressure of water and the contain only have a certain concentration of vapor but the amount of water in the bottom can see anything as long as it's not but it does not evaporate and if the pressure is higher then the vapor pressure that means that if I had the thing in piston and the pressure is higher than the vapor pressure but the Pistons comes down right on the surface of the
1:05:36
water there's nothing less it's 100 per cent water once the date once the pressure exceeds the vapor pressure as long as there's nothing else in there when and if it's exactly the vapor pressure I have a defense of article about like that a lot of paper and a little water a lot of water and a little vapor and therefore had a genius equilibrium we don't have this fraction so that goes with this and that it's usually fall or nothing and we decide based on looking at the reaction which way will reaction go well this is pretty obvious it's carries large we're going
1:06:23
to get products if K is small we're going to stick with the reactants indicators 1 the delta G is 0 they're going to be present in roughly equal amounts but not exactly equal because we could have 3 halves of hydrogen and onehalf of nitrogen for example and so they would be in a threetoone ratio if I have a reaction like this 1 propane 1 ProKey going back and forth to cyclo propane you need to know what these are right now but there 3 carbon molecules and let's suppose Casey is 1 for this Paul Casey is the concentration of the products over the reactants at equilibrium and that's what and if I just multiply through by a concentration of 1 protein I come to the conclusion that the concentration of cyclo propane and equilibrium whatever it is is equal to the
1:07:28
concentration of 1 protein so it's 50 50 of caves near 1 you can thank it's gonna be a big match the big mixture of then you have His used them himself and is negative it's going to be all products In this case timing it's going to be all reactor you are going to get much material OK let's do you want more let's try to decide if we have
1:08:02
an initial conditions whether the reaction both backwards or forwards from where we started because sometimes we have to figure out some somebody does something into a river by mistake and we have to figure out if it's going to precipitate orbits going to dissolve groundwater and what we can do the lot down maybe so it doesn't get in the ground water so we have kind of clean it up and we'd like to know how much of whatever we're gonna had we need that because we don't have too much that usually cost much must and sometimes if we had too much a lot of it'll be left over and we have to clean that up because it's not supposed to be there in the 1st place but we can decide which way it's going to shift fairly easy if if if the reaction quotient wherever you start is bigger than that means you've got to many products and that means that if you started this condition With too many products the reactions actually going go backwards so the the equal of the reaction just to the left the products excuse me the reactor and always right react in sunlight if he was smaller than case that means we have made enough products then the reaction will run forward until it makes snuff products so that few comes up to the value of k and wants water lines reports is going to sit there and as you equals
1:09:47
K nothing further happened that we can see in terms of measuring concentrations they still run both ways but there's no net change still lots of chemistry occurring but no net change the lest you 1 example so at
1:10:10
1400 Kelvin Casey is 4 . 7 this is the 1st state to the heart of process where you you take methane and water hoses things you can get a hold of Newmont and you get carbon monoxide and height the People's and because you're making more malls again last year you predict that this reaction and the favorable roughly speaking you here because of that Gulf that's that's why the heated up like crazy making this and if we know this spellings 4 . 7 and we start out with this concentration 1 0 3 5 molar rates 2 0 . 0 5 bowlers methane . 1 5 molar carbon monoxide and point to Mohler age 2 which direction is a is it going to make us more Of the hydrogen or we gonna lose archive while we just put in the reaction quotient and we have to put in the hydrogen Q you because there's a 3 and then we put in the numbers carbonmonoxide . 1 5 hydrogen .period 2 Q 1 0 3 5 . 0 5 and we get accused . 6 9 but K is 4 . 7 so because Q is less than 10 we're going to make more hydrogen if we run this reaction we can start like this and sit there and we will get more hydrogen power then what we started if you were bigger than that and we would have to to muttered something there and that it was wrong back
1:12:07
OK I I think that's plenty for today
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