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# Lecture 12. Aqueous Equilibria Pt. 1.

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#### Automatisierte Medienanalyse

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understand I can move really fast because we've done many problems of this type role once again just applying what we learned before can that 1 right the I stressed out with my initial concentration the . 0 5 0 0 I'm not concerned about water I have 0 0 to begin with but I wanted to go with the changes made next plus 6 plus X not concerned about water at
equilibrium I know this will be . 0 5 0 minus X X X so we're looking at key because this is the formation
of hydroxide from the weaker confident basis at 4 kb equals 5 . 6 8 times 10 to negative 10 which the concentration of the acetic acid finds the concentration of hydroxide divided by the concentration of these right so that gives me extra where overlooked . 0 5 0 0 minus X right and as always we know we can approximate there's 2 x squared over . 0 5 0 now did you guys know how to solve this I would like to try this at home you have to check the validity of the approximation you calculate acts after you checked for validity of approximation so on X will come out to be 5 . 3 3 times 10 to negative 6 smaller so we know that the hydroxide and concentration equal X which is 5 . 3 3 Contents tend to of smaller Member we need to cap pH signing to convert that to I during concentration which is kW divided by the hydroxide and concentration which is 1 times 10 to negative 14 divided by by 5 . 3 3 times 10 to the negative 6 more this will be more squared and therefore the work that out it comes out to be 1 . 8 8 times 10 to the negative 9 smaller therefore pH equals 8 . 7 2 7 remember we said adding "quotation mark was coined the pH has to be greater France 7 because that solution is facing our right insult we've figured out what the pH of that solution is at the equivalence .period objective now I need to be able to calculate cell if you look at the 4th scenario you need to be able to calculate the pH after 100 . 0 5 milliliters of India which is added OK now the solution to the US is very similar to the strong asset because once we passed equivalent .period now although after visiting consumed completely and all you have is a strong base are right and so the solution for this part will be exactly the same as a solution for the previous parts because what you have is now at the close .period you about 100 ml of the base now you have an accessible . 0 5 are right so that solution that have a strong base and a week later and astronomers is much stronger than the be base to see them so the major contributions will come from the strong base so you have a point of 5 milliliters of excess hydroxide all you have to do is calculated the number of molten . 0 5 ml of hydroxide divided by the total volume which is 200 . 0 5 and that gives you the concentration of the strong base and because strong associates completely you know the hydroxide and concentration is and so you know the hydroxide and concentration that comes from that extra point you'll find that was not neutralized all right in the capital of the future that solution OK so you should be able to solve these kinds of problems and discussion for next week actions this week that the discussions actually get you to solve some of these problems I need to be able to look at these different types of problems and to be able to solve them again now a couple of things I want point out actually go back to the graph and I would point out some things on this so thin you look at this titration this is the point at which there is no basis added to usually over-the-counter repeated that we gasses OK we know this region where it flattens out is called the buffer region Abkhazia in this region where flat we call that the buffer region because that's the region where it's going to act as a buffer so whenever you have mixtures of the weak acid and its conjugate base is going to act as a buffer again now this is the equivalent .period all right and we know that the coolest .period the pH will be greater than 7 OK no if you take we already calculated that you have had 100 ml to reach the cruelest .period so exactly half of that is called the have equivalents .period variety and that he had equivalent .period which you realize there's itself at the have equivalents .period what to realize is that the concentration of the acidic asset that's left over equals the concentration 3rd C H 3 C O 2 minus tonight as we write that OK because it's not very clear and don't want to rush that so at the time have equivalents .period we know that the concentration of the acidic gasses that's left or when the flaps that excess amount should be equal the concentration of the acetate find so you know that th equals PKK -minus log of the acid for over the base and these identical equal to each other what we know PHE calls PK minus logged 1 which is peaking minus 0 so we know what the half equivalence .period pH city should people picking so you have articles .period you figure out that the cruelest .period 100 ml here happy goers .period that's the perfect buffet yet equal amounts of pork are right and therefore the pH should be equal to so if that's the case you wanted to any calculations and you get a question saying you know the pointedly equalized .period they ask you once appeared to the solution at this point you're not doing that because you know pH equals became and this gasses a begin acetic gasses about 4 . 7 5 so you know that the pH at that point will be 4 . 7 5 effect now I want to finish up by just put going through this question so this is an old question from an older exams are just full of it this morning and I want you guys to take a look at this and put a copy of this on the class website OK so why is that here we are so out of the question consider the titration of a generic weak acid with a strong base that gives the following titration curves so you have already seen this Caribbean it's a weak acid strong base could obtain all their indicating the points that correspond to the following the 1st the equivalent .period so all of you know at the close .period this tiger magic .period has to be there that is so that they could point to the region with maximum offering so you wanna show it kind of shows where this is plateaus out flattens out this is the region of maximum offering somewhere between this and this and that region that PAT equals the where would that you look at the equivalence .period it's a little above 25 are right in 30 years at somewhere between states it's actually summary fear right in the middle so you have to look at this value and divide that exacted by half and that the interview with PET was
and that would be point their take pH depends only on the initial concentration so this would be a subscript OK and so on it depicts depends on only the initial concentration of weak acid where would that 0 before you add in the case that would be the point at which Piech depends only on the conjugate base at the close .period because the cause .period is the only point at which you have exclusively just the constant base last pH dependent only on the amount of excess strong base added so where would that be where the pH depending on the amount of strong base anything past cocoons .period so once you pass this all these points when surpasses anything about that will depend on the concentration of the hydroxide OK so will stop
there today and next time we want next topic the
Chemische Forschung
Säure
Besprechung/Interview
Setzen <Verfahrenstechnik>
Titration
Konzentrat
Chemische Forschung
Base
Asthenia
Konkrement <Innere Medizin>
Periodate
Lösung
Natriumchlorid
Malz
Kochsalz
Hydroxide
Wasser
Asthenia
Aluminiumsalze
Elektrolytische Dissoziation
Arzneimittel
Konkrement <Innere Medizin>
Lösung
Gasphase
Reaktionsgleichung
Spezies <Chemie>
Eisenherstellung
Säure
Molvolumen
Ale
Weibliche Tote
Acetate
Natriumhydroxid
Konjugate
Neutralisation <Chemie>
Aktivierung <Physiologie>
Reaktionsführung
Chemischer Reaktor
Setzen <Verfahrenstechnik>
Gold
Natrium
Base
Chloridion
Essigsäure
Genort
Thermoformen
Arsensäure
Titration
Bohrium
Pech
Periodate
Chemischer Prozess
Elektronendonator
Wasserscheide
Konzentrat
Hydroxide
Optische Analyse
Wasser
Asthenia
Konkrement <Innere Medizin>
Lösung
Gasphase
Spezies <Chemie>
Säure
Molvolumen
Rohöl
Stoffmenge
Natriumhydroxid
Acetate
Konjugate
Aktivierung <Physiologie>
Fülle <Speise>
Wasserstand
Reaktionsführung
Chemischer Reaktor
Base
Essigsäure
Protonierung
Pufferlösung
Blei-208
Bleifreies Benzin
Thermoformen
Mischen
Titration
Periodate
Chemischer Prozess
Malz
Kochsalz
Konzentrat
Hydroxide
Wasser
Asthenia
Lösung
Gasphase
Säure
Wildbach
Molvolumen
Natriumhydroxid
Acetate
Konjugate
Zelle
Aktivierung <Physiologie>
Reaktionsführung
Chemischer Reaktor
Setzen <Verfahrenstechnik>
Natrium
Base
Essigsäure
Dampfschlepper
Protonierung
Titration
Initiator <Chemie>
Katalysator
Singulettzustand
Periodate
Acetate
Konjugate
Zelle
Aktivierung <Physiologie>
Wasserscheide
Schweinefleisch
Setzen <Verfahrenstechnik>
Konzentrat
Hydroxide
Base
Asthenia
Elektrolytische Dissoziation
Essigsäure
Lösung
Konkrement <Innere Medizin>
Gasphase
Azokupplung
Auftauen
Pufferlösung
Mischen
Säure
Titration
Periodate
Konjugate
Säure
Säure
Paste
Hydroxide
Initiator <Chemie>
Konzentrat
Topizität
Base
Asthenia
Periodate