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# Lecture 06. Acids and Bases. Pt. 3.

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#### Automatisierte Medienanalyse

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OK I have residential please let's go ahead and on searched quick announcement and that is that I notice that the is during the last 2 days there's been a lot of people and this class all right if you were 1 of those people who added this class to Stephen mind that the online homework that has to be completed and if you're transferring from another class your scores are not transferable so please contact me on if you switch classes the 2nd it is you who joined his classmates I want to remind you that there is a survey that you have to complete by the end of this week are right and so on you will get credit for that completing those arrangements of please make sure that if you transferred into this class that you complete that civilians were again so getting back to where we start last time you guys remember we talk about basis last time and we wanted to summarize the important features of cases we
said that 1st ladies wouldn't draw the same parallels between assets became so strong bases have key greater than 1 we know that week bases have so it would time of basis which became the weak bases have KB less than 1 OK the smaller than value of KB the weaker the base of the 3rd point I want you to remember is substances there have carried less than 1 times 10 negative 14 do
not act as and and not act as a base in water forever because we know now water has a higher GDP and will act as the base rate now lastly we finished up by saying that we derive an expression where we said OK 8 times KB equals the W which is 1 times tents and negative 14 a k gives you the acid dissociation constant for the acid form of the conjugate Aceves spare and KB gives you the biggest dissociation constant of the conjugate base of that assets are right and so we said that very often only Kaizer listed in Tables and so on you want to the conjugate base and you want to keep the value that cost constant constant based on you have to do this can working 2 he alright analysts said that since the scale the enormous we also look at it in terms of a logarithmic scale and so we said he'd take the negative log of Kate and the negative log of TB that will give you more than negative log of CW and so that gives you picked it plus PKB equals contained W a right which as all of you know is equal to 14 so if you revert back to notes from last class in my I wrote PKW 1 times 10 negative 14 sitting across that out and make sure that you don't make that mistake are right and that it is actually 42 right so this is worth remembering because now you remember that basic fundamental innovation in information now makes it easier to solve problems so take some examples and you remember I just you that task and I hope the completed because I'm quickly go through the answer now to be guys remember we look at a problem last time where we were looking at calculating the pH of a weak acid and we were told to begin with we have 1 mole of the acid dissolved in 1 liter of water so we know the concentration is molds for leader and therefore To begin with we know the initial concentration of acetic gasses and so on the initial concentration of acidic gasses given here it's given to 3 significant figures cell will will place that there and of course to begin with and we have no reaction taking place this is at the point at which the reaction starts at that time 0 alright so because we have some 0 . undermined in 0 acetate I and all of you recognize that the reaction is to proceed in the forward direction are right and the reaction is proceeding in the forward reaction direction we know that the amount consumed or the amount reacted with the negative that amount form would be plus X plus 6 right and therefore at equilibrium would have 1 minus X X X so we kind of keeping track of the concentrations of all the species that there the solution and we know that we're looking at the acid dissociation constant and therefore but that is 1 . 7 6 times tend to make it fight so we know carries 1 . 7 6 thousand 785 that equals the conservation of the mind times the concentration of the acetate and I'm divided
by the Constitution of acetic acid which gives you it's squared over 1 minus X now I never look indicated value assistant to the negative 5 so this is an enormous small numbers and so we know that is a small number of the reaction is proceeding in the forward direction and the extent of that reaction is that we will it's small it's gone awry and therefore we know that X is going to be small and so it is safe to make approximation and so we made the approximation and you can see that once I make approximation things get to be really simple so I know 1 . 7 6 times to the native 5 would be x squared for 1 and therefore the software he comes out to be 4 . 2 0 times 10 to the negative 3 smaller right the end so I once you know that what we need to do next you have to balance a member of the Mende approximation you have to check with the approximation is valid that is validated so validate approximation and William valid approximation remarks approximation is that X is really small compared to 1 which is 4 . 2 times tend to native 3 Moeller divided by 1 molar times 100 which gives me a 0 . 4 2 per cent so that falls well below what threshold are right and what is is means is added that we can make this approximation are right and so now that I know this is valid I know that the high junior mind concentration equals acts which equals 4 . 2 0 times tend to native 3 Moeller and another to concentration I can take the negative log that and that comes out to be 2 . 3 7 7 right again this is a 3 significant figure number therefore we knew recorded in pH given good 3 decibels right now that the 1st part of the southern part is calculated as the percentage associations are right so the percentage dissociation or Percent decomposition of sent ionization would be the amount that disassociated which is X once again divided by 1 molar times 100 and therefore this would be 4 . 2 0 native 3 Moeller divided by 1 molar turns 100 and we just did this calculation to check validity as well announced . 4 2 per cent so what exactly it means that for every 1 thousand molecules of acetic acid that you put four-wheeled associate systemic sensor supercenters could dissociation gives you the percentage of molecules of city gas molecules that associated so every thousand molecules that you put in water of acetic acid only four-wheeled associate so that is a really weak acid is that it can erase the that's because the opposed that if you had a strong acids what would a strong acid fight with thousand molecules of acid in the water with strong acid you all 1 thousand would associate right so there a dramatic distinction between strong acids and we take no notice sometimes noted that all carried out online homework and you see some of these problems come up the online homework and sometimes the reverse is given to you are at sometimes thinking the process Association and Jurassic calculated in for sometimes year given the pH of the solution and asked to calculate the initial concentration so there given the pH of the solution what would this strategy given the age when you want to convey that to the 100 my concentration allowed the height high-demand concentrations are right now wants to know all the hydrodynamic concentration if you know what Casey is now high during my concentration is the concentration at equilibrium so that means that all you have to do is to just working backwards to see that the problem we're now it is solving a problem that tied all you have to do is now you don't have to look at initial change equilibrium all you have to do is look at us and you would say it this is a hard during my concentration and this is not to undermine concentration this estimate same as that of the president and this is what we need to find out what is my concentration at equilibrium right and my concentration at equilibrium will be approximated to be similar to the initial concentration is an extensive ready because for all the case's this Texas so small you can approximated all right and so what you doing it says it is working back backwards if you know what the nature of the equilibrium concentration of High junior mining is you equal and concentration that I joined in mind you can calculate the initial concentrations of the gasses case so using these kinds of problems coming up In homework and now we should be able to solve all the problems and where you don't can get many different variations of this and you should be able to solve them illustrate 1 last example before we move on to the next topic Connecticut example of navigate so here we have calculated so now we're looking at calculating the pH of economy based on the quality of these incidents that you what so we calculate the pH of a solution made by dissolving . 0 0 1 moles of ammonia and enough water to give 1 leader I hate is given so once again the starting point is for you to recognize that year starting with each Street and we know that in its 3 acts a basic water all right and you're not sure go to the table and look at the balance right said you take ammonia you can see that ammonia should be somewhere in here keep going down so there we are when prices were there and so on here's ammonia This is the basic form this would be mean it's a city form the ammonia down here is way below this and we know that ammonia can act as acid and water can see so because water is a stronger base ammonia has arrived so this can add to that acid water so so if I take ammonia than equilibrium that would be established with the In each 3 plus liquid water giving me for what I did it's for class which is the conjugate acid and which minus and CAB is 1 . 8 times 10 to the negative 5 peso you have to identify what equilibrium is and you have to identify with act that acid water with an act as a base because this acts as a basin water equilibrium expression would be key right so we've written information down now and we need to start the initial concentration so the initial concentration of ammonia is . 1 moles in
1 liter case so that means you have . 0 1 molar solution to begin with but not concerned about the concentration of water and before any equilibrium take a reaction takes place wouldn't have 0 products being form so once again we know that establish equilibrium the reaction to to proceed in the forward direction therefore change would be negative assets plus 6 plus and equilibrium the concentrations would be . 0 1 0 minus X that's that's right so we follow the same process that we did but we calculated the pH of gasses are right but here we are now looking at KB so KB holds 1 . 8 times tend to negative by which gives
us the concentration of the conjugate acid each for plus times hydroxide irons divided by but the concentration of industry which gives me that square over . 0 1 0 minus X alright now if you want to you can solve a quadratic equations that take you longer but as all of you know you look at the kid value KBE is 10 to the negative 5 so you might as well take the approximation and check the validity or right so it really made the approximation we know that .period 0 1 0 minus X will approximate 2 . 0 1 0 and therefore we can say 1 . 8 times since the 95 gives me X where over . 0 1 0 therefore himself X we're going to 2 significant figures so it comes out of 4 . 5 times 10 to the negative 4 . 2 times 10 to the naked eye for more OK so what that means is that we calculated that and so in this equation commemorated the devil we're calculating hydroxide concentration so hydroxide and concentrations of assets equals 4 . 2 times tend to negative for knowledge but is that what they asked us to calculate what we need to figure out pH so that means I want P H I not convert the high during my concentration figure how much I'm sorry the hydroxide and concentration converted to hide to undermine and figure out how much had to undermines their solutions are right and so there 2 2 ways its offer this 1 way is to say we know that the high journeyman concentration equals kW divided by hydroxide and therefore that the 1 times tend to make negative 14 divided by 4 . 2 times tend to negative for and that number comes out to be 2 . 4 times tend to negative 11 bowlers and now that I know the high journeyman concentration I can't figure out pH which comes out to be a 10 . 6 2 now I've taken a lot of that number and that gives me the pH because we're carrying 2 significant figures the answer goes to 2 vessels right now not only do this is to take the hydroxide repeal appeal wage taken a lot of that appeal weights in subtract from 14 and you should end up the same answer William round off again any questions up to this point so now I know you really need to spend some time practicing problems involving acids and bases are right and the that we've assigned and also the problems that you're working in discussions will come into force that are right now over it and move on to the next topic and the next topic will look at our holiday proteins so if you remember up to this point we have looked at Monaco protein acids all right up to this point examples that we
look at Amon approach gasses the these are asses that have only 1 this sociable Proton or some other part of gasses are acids that have only 1 the social Protocol so examples that we looked at were things like when they get ECL this as 1 the sociable Proton
strong acids and has won the social protest we looked at acidic gasses and we said we would know if you look at the structure of acidic gasses and the structure has 4 hydrogen atoms only 1 among those is actually sitting in his 2 sociable so once again acidic gasses it is a modern you take something like hydrogen cyanide that someone protests is if you take a chance that someone of broadcast are right and if you take something like formic acid that is also home Monaco itself you look at the structure formic acid it has 2 hydrogen atoms in a molecule remember every hydrogen atom in a molecule does not have to be a sitting on right and so these are all examples of molecules that are more prone to write Polly Prodi gasses have more than 1 the Social Protocol and examples include examples lied and H 2 and right remedies are all in a liquid solution so we can say that there a solutions and so when the solution and you can see that now this has to the social programs both of these protons can come I write another example would be age to seal to read or write H 2 S O 3 but these are all examples of polystyrene gasses and if you look at this all of these have to be sociable protons their called died Prodi Carson's Tonight acids had to be sociable protons right now other examples include like you can have Peachtree to be appeals for now this has to be protons and there would be like it's 3 AM schools for closed so these had come are called tried protested and Tripura gasses have 3 this sociable protons so all of these are collectively called Polly predicted acids are so another look at masses that have more than 1 2 sociable protons are right in that state some examples was started by looking at something light on sulfur gasses so it turns out that you take Polly product gasses polymer-coated gasses dissociate in a stepwise all right so we look at the Association of protons from a polyploidy gas each proton comes out sequentially instead wise alright so inviting example like sulfuric acid let's start with sulfuric acid so all of you recognize that sulfuric acid is H 2 for and that it has 2 protons that can be dissociated all right so what happens is that 1st 1 proton comes after you take H 2 SO 4 and this is water member this is the acid and this would be the base are right and
so on the protons come stepwise right in sequence or so 1 1st the 1st proton will come off and when the 1st proton Macedonians that protons to the water which is the basis which you end up with is to your plants now you take H 2 SO 4 and pull a proton off what you end up with a chisel for work member charged balance it's going to be a status of all miners OK because you took a months or that we use this has to be beaches so for minors equipped with
check is on the reactor side you can see that everything is electrically neutral I therefore on the product side we know that the high during mine has a positive charge therefor this has to happen charge right and this is the conjugate assets and this would be the conjugate base now since this represents acid dissociation we call this case wanted because no this refers to the 1st proton coming off a sofa polyploidy gasses we will call this the 1st acid dissociation constant or the 1st acid ionization constant right because this refers to the 1st proton coming out now in the case of sulfuric acid and this number is of the order
of 10 to the 2 are and so it is of the order of 10 to the 2 so the 1st proton coming off does that act as a strong acid was acting as a weak acid Strong and because the acting as a strong acid we know that the 1st proton coming off will be a complete association so all although H is 0 4 were converted a shield lost and ages of 4 minors because now it's acting as a strong acids are right now the 2nd step will involve a 2nd Proton coming out so now we take this are at this species that is formed when 1 proton has been taken up now sequentially the 2nd Proton will come out and you end up with when you think the product is going to be now if you take it is awful as an upholder proton out what it what we be left with a soulful what to minus alright so once again we are maintaining charge balance and check on the reactants side start with minus 1 and therefore on the product side you have to have minus 1 as well so you have a plus here this has to be to minus civilian result is that you have charged balance now since this involves removing the 2nd Proton recalled that hate to and came to it turns out to be and you know what you can find these values in this table and I'll come back to that but it turns out it is 1 . 2 times 10 to the negative too all right and so for the 2nd step now and then is the asset this would be the biggest ever the reverse reaction this would be a conjugate acid and this would be the conjugate base all right and with his equilibrium is established the equilibrium constant that corresponds to the 2nd equilibrium is 8 2 and we call that a 2nd acid dissociation constant are now let's take a look at the data so far minus that his former can you see that in the 1st equilibrium pictures of all miners is at the time as a base it's a condom debates right says something that acts as a basis in the 1st equilibrium now acts as 1 the 2nd equilibrium as an acid so you can see that it is of all minors is actually acting as an asset as well as a base alright and what we call substances that act as an acid as well as a base and terror so you can see that in this it is so for minors years and for or so that when we consider that this is In a step-wise process and we say that is up to competing equilibrium that are taking place at the same time I write to you having 2 competing equilibria occurring at the same time the 1st involved in the probe mission the 1st proton and a 2nd step involves the deep procreation Of the 2nd protest all right so now I wanted kind of before we start many calculations you should be able to look at his entire picture and kind of figure out what other major species so once equilibrium is established these competing equilibria taking place what did think will be the major species all right so let's the 1st at the 1st 20 Clemens established is into its products into intuitive reactants product and have lots of it's your plus images of 4 miners because of the strong acid for all intents and purposes we can say that it is 0 2 is so for that that number is still small the winner during our right to about the 1st what is the major species it's your class and it is a full all right now let's the 2nd step the 2nd step exactly as a weak acid there when you have a weak acid those that rely on the reactants site the supply and the products react so for the 2nd equilibrium much of it is going to be it is local minus see and there is little that is going to go to and soulful miners and it's your plots does that make sense so all we can say is is in in this equilibrium mixture we can say at equilibrium Major certain if you want have a feel for what that been composition looks like the major species are going to be aged 3 or class an agent so for minus and the minor species be and so forth to minus devices that are right and went on to consider it itself to to be a minor species because it's a strong acid and to Estillfork will dissociate completely and so the amount of extra whistle for that's left over is gonna be so minuscule hardly anything at all all right and so this is where the women composition would look like all right behind during my concentration comes from 2 sources this will be a large amount of mind coming from this step in and there's going to be a tiny amount of hydrogen coming from this so between India's this amount is going add about 100 miles from the 1st to that you see that but the amount that comes from this is so small that you know adding these 2 together will be will amount to adding that to see that just that component all right no mistake another example of a dyke Prodi gasses and in this case let's take carbonic acid survived carbonic acid which is aged 2 yield 3 bond together to divert gasses and the diverted acid I can ride the 2 competing equilibria right so the 1st step would be H 2 sealed 3 8 West plus water giving me 8 3 0 plus the worst plus 8 sealed to remind us that this is the acid this is the base conjugate acid conjugate base and now the 1st association constant for carbonic acid it is I 4 . 3 times 10 to the negative 7 right the next step will be the 2nd Proton coming off now what is a will act as acid and this will now approach a water to give you high joining mine plus 3 to minus quest and this is K 2 and K 2 comes out to be 4 . 8 times 10 to the negative level all right so it might take carbonic acid which is able to see all 3 the 1st step it acts as a strong as a weak acid the we have
know that the initial concentration is given so the initial concentration of this is 0 . 0 3 4 more this is the amount before any reaction takes place so we know that this reaction proceeds in the forward direction therefore the change would be where the reactant is consumed and products are formed right so I'd call equilibriums we have . 0 3 4 minus X this'll be X and X are right so we can say care of equals 4 . 3 negative 7 equals the concentration of high join mine times the concentration of its 3 or minus divided by age 2 sealed 3 which gives me at square of . 0 3 4 McCain the absurd at minus X and will make approximation can so we know that this numbers tend to the negative Sabine so the extent of the reactors will be was small we not X is going to be small so we can approximate that an approximation is going to be that . 0 3 4 minus X will approximate 2 . 0 3 4 right so for . 3 times tend to 87 gives me back square of a point 0 3 4 therefore can offer acts and with those values in your calculator the number that you end up with it is 1 . 2 times 10 to the negative for Moeller was that set up the right number Our city but that it happened that's what you end up with if you check them eliminating malaria would be 1 . 2 times tend to negative full Moeller divided by . 0 3 4 times 100 and that comes out to be . 3 6 cent so you know that's well below your threshold from approximation so we know that this approximation is valid and so on now I can say is I know what actually I can say that mine H to C O 2 concentration would be . 0 3 4 minus X which is . 0 3 4 minus 1 . 2 times 10 tonight before which actually is . 3 for the amount is so small that does not make a difference in this number within the oversee things are right so buy 1 accounted ahead John mind concentration high joined in my concentration is 1 . 2 times 10 to the negative for smaller and my 8 0 3 miners concentration is 1 . 2 times tents negative mall 2 more days so this is the concentrations that are related to the 1st equilibrium all right now we need to look at the 2nd day of the 2nd it where now it's yield 3 minus quotas gives me H 2 react to the H 2 or to give me aged 3 or plus was less sealed 3 2 miners request and this would be OK and gave to it is 4 . 8 times 10 to the negative level right so now for the 2nd stab my initial concentration would be the concentrations that come from the 1st step in everything because there will be a stepwise manner so what would my concentration of a sealed 3 correspond to it should correspond to the number here are right so to begin with I have 1 . 2 times tend the negative for not concerned about the concentration of water here what will my concentration of high joining Miami with physical Missouri no we already have a joint in mind that comes from the 1st step receiver in the head during mind that comes in the 1st step would be the best so this would be 1 . 2 times to the negative for in and out the 0 so for the 2nd these are my initial concentrations of all the species for the 2nd step so now I'm going to look at change and just don't distinguish between the that's up there from the values here and said this is going to be negative why I write this this will be plus wife and this will be a plus Y right therefore at equilibrium I would end up with a 1 . 2 times tend the negative for minus why over-the-air I joining my concentration would be 1 . 2 times that the negative for plus twice and that would be wise all right so long now I'm looking at the 2nd step out and in the 2nd step I can say 8 equals 4 4 . 8 times 10 to the negative 11 which he calls the high joint airline concentration time sealed 3 2 miners divided by age sealed 3 miners which gives me 1 . 2 times since the negative for plus Y times why divided by 1 . 2 tons said the negative for -minus wide 10 the are cases tend to the negative right so I knew that I can make this approximation because the caveat is so small that we know the relies entirely on the reactor reactants inside so binding approximation that 1 . 2 times tend the negative for last why would approximate to 1 . 2 times tend the negative 4 and 1 . 2 times detonated native -minus With approximated to 1 . 2 times tend to negative for right and and want to make this approximation I can say that 4 . 8 times tend the native 11 equals 1 . 2 times tend to make it 4 times y divided by 1 . 2 times tend to negative for both of those cancel out so why gives me 4 . 8 times 10 to the native 11 Moeller I write and at this point you should check validity I write and I just skip that step but can you guys check Bolivia at home you have to check with Y is rather small compared to that you can see this is tend to think in London this is designated for that number is really small OK and so on we can finish up by saying that the sealed 3 2 miners concentration would be 4 . 8 times 10 the negative 11 right and in fact we can see that there's actually equals K 2 because these 2 concentration will always cancel your company concentration people will come out to be that scenario
analysts doubt the concentrations of all the species you know the concentration of H 2 0 3 in the conservation of field last year the concentration of people 2 minus 10 .period
Besprechung/Interview
Bukett <Wein>
Chemische Forschung
Lactitol
Bodenschutz
Oktanzahl
Konzentrat
Wasser
Schwache Säure
Lösung
Gasphase
Spezies <Chemie>
Säure
Zunderbeständigkeit
Narbe
Dissoziationskonstante
Acetate
Konjugate
Zelle
Aktivierung <Physiologie>
Begasung
Reaktionsführung
Base
Genexpression
Kalisalze
Arachidonsäure
Säure
Johanniskrautöl
Biskalcitratum
Thermoformen
Initiator <Chemie>
Wasser
Methyliodid
Edelstein
Verrottung
Konzentrat
Wasser
Elektrolytische Dissoziation
Elektrolytische Dissoziation
Lösung
Konkrement <Innere Medizin>
Computeranimation
Gasphase
Reaktionsgleichung
Mergel
Ammoniak
Altern
Konjugation <Biologie>
Säure
Molvolumen
Dachschiefer
Molekül
Systemische Therapie <Pharmakologie>
Lösung
Konjugate
Aktivierung <Physiologie>
Schmerzschwelle
Reaktionsführung
Einzugsgebiet
Topizität
Base
Genexpression
Essigsäure
Stoffgesetz
Essigsäure
Säure
Wasserstoff
Biskalcitratum
Thermoformen
Initiator <Chemie>
Kettenlänge <Makromolekül>
Chemischer Prozess
Konjugate
Aktivierung <Physiologie>
Ammoniak
Entzündung
Konzentrat
Hydroxide
Topizität
Lösung
Computeranimation
Gasphase
Neutrale Lösung
Membranproteine
Eisenherstellung
Körpergewicht
Bukett <Wein>
Säure
Atom
Lösung
Konjugierte Linolsäure
Mineralbildung
Hausmittel
Schweflige Säure
Diatomics-in-molecules-Methode
Blausäure
Ameisensäure
Chemische Forschung
Base
Wasser
Elektrolytische Dissoziation
Lösung
Reaktionsgleichung
Gasphase
Protonierung
Altern
Chemische Struktur
Säure
Polystyrol
Sekundärstruktur
Chemieanlage
Molekül
Sahne
Sulfur
Mineralbildung
Matrix <Biologie>
Gensonde
Konzentrat
Wasser
Elektrolytische Dissoziation
Konkrement <Innere Medizin>
Schwache Säure
Computeranimation
Reaktionsgleichung
Gasphase
Altern
Spezies <Chemie>
Chemische Verschiebung
Sense
Säure
Chemische Bindung
Gleichgewichtskonstante
Aktives Zentrum
Mühle
Konjugate
Gang <Geologie>
Aktivierung <Physiologie>
Hydrierung
Kohlensäure
Schweflige Säure
Wasserstand
Reaktionsführung
Chemischer Reaktor
Quellgebiet
Gangart <Erzlagerstätte>
Base
Kalisalze
Arachidonsäure
Protonierung
Säure
CHARGE-Assoziation
Mischen
Fließgrenze
Chemischer Prozess
Matrix <Biologie>
Wasser
Phosphorsäure
Konzentrat
Wasser
Schwache Säure
Computeranimation
Eisfläche
Spezies <Chemie>
Konjugation <Biologie>
Schwefel
Säure
Zelle
Begasung
Kohlensäure
Schmerzschwelle
Reaktionsführung
Base
Protonierung
Thermoformen
Fließgrenze
Cocain
Arzneimittel
Mineralbildung
Monoaminoxidase
Zwilling <Kristallographie>
Kluftfläche
Sonnenschutzmittel
Chemische Forschung
Hydroxylapatit
Elektrolytische Dissoziation
Lösung
Konkrement <Innere Medizin>
Gasphase
Altern
Elektronegativität
Aktivierung <Physiologie>
Physikalische Chemie
Schweflige Säure
Wasserstand
Chemischer Reaktor
Brauwirtschaft
Quellgebiet
Gangart <Erzlagerstätte>
Magma
Säure
CHARGE-Assoziation
Bleifreies Benzin
Harnstoff
Oszillierende Reaktion
Hydroxybuttersäure <gamma->
Sprühgerät
Bodenschutz
Spezies <Chemie>
Konzentrat
Periodate