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Lecture 21. Electrochemistry Pt. 6.

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it but OK ,comma can I have a room detention please and so on was going and before I begin I wanted to know of any questions all right so you guys remember on we talked about the relationship which we in the cell potential and equilibrium constant last time and we in expression and this
comes from we know that the relationship between free energy and equilibrium constant is Delta Jeannot reaction equals minus R T L and case we let this last quarter we looked at the and we look at the relationship between free energy in the equilibrium constant now we also know that Delta Jeannot reaction equals minus and have even on south that's the relationship between the cell potential in the free energy and therefore we can say and have you not sell equals negative RT Alan Keyes and so now we can rearrange the get rid of the Commission signs we can even get rid of the person a L the walls and have work t he nods for me he said he sell equals party over and Alan Keyes said depending on what we want calculated he can rear this equation to get rid of this or that and then we said that the view are hours a constant it's 8 . 3 1 4 5 jewels press Calvin from all we said that temperature is absolute temperature and room temperature of history I'm sorry I can't temperature is Kelvin temperature in Everett 25 degrees Celsius then this would come out to be 298 . 1 5 Calvin and lastly we that's it is fairly constant which is 9 . 6 arms 4 8 5 cool alarms from all and so we put this in and we end up with our priority over an equals 0 . 1 0 2 5 6 9 3 2 0 . 0 2 5 6 9 3 balls and put that value in there and so it should end up with is Alan Keyes equals and was 0 . 0 2 5 6 9 3 balls before we can say we can write that like that or we can say not sell equals 0 . 0 2 5 6 9 3 balls divided by 10 times Alan Keyes or so now we have a relationship between the equilibrium constant in the sell potential so let's take an example where we apply this case determined that problem on the on the worksheet and and surviving change this to the problem you can see that you're asked to calculate case which is equilibrium constant for the reaction that we've been looking at all along which is the reaction in the Daniel cells and we know that the seller potential for the Daniels cell is 1 . 1 0 volts and survival account equilibrium constant canaries see that this would be making use of this equation over here organs that Alan K. equals and not sell over 0 . 0 2 5 6 9 3 cell look said Alan Keyes equals 1 In which is the
number of electrons being transferred the not cell divided by 0 . 0 2 5 6 9 3 walls now we know we've seen previously that the downhill so we know to electrons having transferred in and gives you the number of moles of electrons being transferred so that would be too the cell
potential we know for that is 1 . 1 0 volts now if they don't give you potential you look at the balanced equation you figure out what is the reaction of Indiana what is the reaction of the capital would you go electrochemical series of the table of reduction potentials and you add them together you take the reaction for the capital would you take the reactivity and notice which the sign add them together and that will give you the cell potentially going to get the cell potential from the tables you figure how many electrons are being transferred
and then you put this in here and the survey's 0 . 0 2 5 6 9 3 volts holes in
walls would cancel out which gives you 85 . 7 right and then by taping the side of that today comes out to be 1 . 5 times 10 to the 37 so you can see but these reactions the equilibrium lies entirely on the product side so includes establishing get lots of lots of products being formed all right now you look at this reaction can receive that we're looking at case OK it represents the concentration the products divided by the concentration of the reactants are right now they're solid C and we know that the of solids the not include them in the aquarium expression so K is really the concentration of zinc to plus signs which the products divided by the concentration of copper to all right and so
this is 1 way in which you can determine that equilibrium constant for a reaction because the center which you do is you can look up the appropriate oxidation reduction reactions and from that you can get elected you know from the standard reduction potentials you can figure out which is oxidation half of the reaction we can figure out what is a reduction half of the reaction to figure out the the potentials that correspond to the oxidation half the reduction have added together .period the cell potential plenty cell potential if you put in this equation and you can figure out the value of equilibrium constant alright right yes why king and his wife is it wiser to significant figures because of accident but we are going to 3 significant figures here are right hand and so if you work strictly keeping track of 6 figs and you just take the decimal because you're taking the inverse farther back OK so strictly speaking you would end up with a number that is once and for all right but I'm just hanging over so here are not keeping track of 6 things aren't so you just doesn't make sense everybody this is we're taking the inverse log of this number and we go from the logs scaled to the regular scale you will look at the decimals all right and so they would turn out that this number should be here to be practicing things shouldn't happen 1 significant figure guidance OK so we talk about the fact that for any reaction you can figure out what the equilibrium constant is as long as you can identify the opposition have the reduction half of their reactions occur no I wanted him summarize so the relationships that we looked at an adult when you are looking at the wooden it's alright any water relate delta G which tells the utility of spontaneous reactions you know delta genes should be negative is on spontaneous reaction you would be positive and the relationship between Delta genes and equilibrium constant was given by this equation where we adopted G equals minus RTL and caring and if you want to look at the relationship between delta G and sell potential we know that reaction that relationship is given by Delta G equals minus and not sell and then you will look at the relationship between the cell potential anchored that's the equation that we derived all right today and so whatever you have to convert from 1 to the other this kind of trial shows you the relationship between the quantities the relationship between Delta gene on the cell potential an equilibrium constants in resolving problems depending on what you need to calculate you can use that to figure out the relationships Zakaria when Soderling said that we're going to look at that sort of worried about the last topic that we look at it from the galvanic cells and that is the nearest equation they sell you're copying this I give you a moment to copy down all right so yes yesterday that comes from the limits RTL always at Soros the gas constant which is in SI units residuals for Calvin from all at times team which is the temperature which 298 . 1 5 in an effort is very constant OK so put those numbers then you should end up with that OK so if we now move on to looking at the last topic that we want look at what we do a galvanic cells and that is what we call the nearest equation know what we started looking at galvanic cells were the things that we talked about was that for any bad really or any galvanic cell we know that as the batteries being used up at some point the battery gets spent all right and so usually what happens is when we deal with galvanic cells we start under standard conditions severely with the Daniels cell wouldn't have 1 will accompany ,comma concentration of zinc ions 1 molar concentration of copper ions in and we have zinc metal and copper metal and at that point we connect the CA because the concentrations are all under standard conditions the voltage that measure and that will be there would be 1 . 1 0 waltz OK now once the battery starts working what's gonna happen is the concentrations of the change the concentrations in Donald where we have the zinc their concentrations I wouldn't change and on the other side of the copper iron concentrations were changed and so as the concentration changes the cell potential starts changing as well all right and as the reaction proceeds of the sale potential changes as well until Indiana the batteries spent in when the battery spent we said that in equilibrium has been at established established with delta G 0 are right and solar the cell potential 0 as well so what happens is when the battery is spent the center what happens there's that inequality has been established and the reason is that as the reaction progresses the concentrations in both those chambers Indiana the capital will be changed OK so you want to look at the dependence of the cell potential on concentrations then we look at the nearest equation are itself where the nearest equation gives you it is the formula for predicting for predicting that variation but this cell potential when the concentration of of concentrations and pressures is expressed by the nearest equation all right and once again it will be start with the equation that we learned implement amendments now everyone to look at the change in free images as the concentrations of reactants and products change we said that is given by the equation delta G Reaction equals Delta G reaction plus Archie Bell and In remember we said as the reaction approaches equilibrium if 1 look at how free energy changes as the concentrations of your reactions in part part-exchange were using Q because we have an established equilibrium yet the reaction is proceeding
and if you want look at the dependence of the free energy changing concentrations of reactants this is the equation that we use our right now would apply this to electric chemistry and electric chemistry we know that Delta GE reaction will give you minus a and Delpha Jeannot reaction so this there's free energy under conditions were you not under standard conditions this is free energy under standard conditions which gives you the difference of free energy between pure reactants until products are right and this case this'll be understand it states the cell where everything is 1 molar concentration so this will be and have you not sell another take these 2 values included in that equation sort out however is have sell Yukos minus and have you not sell plus parity Alan Q and if I rearranges equation you can see the Sal calls not sell 900 take the science and flipped the signs around so the miners are she or where N F L N Q and we call this the nearest equation in essentially what this equation tells us is that as the concentrations of yourself and your reactions and products In cell changes if you want to look at the dependence of the self tend to have his itself to change as you concentrations of the react and products very that's given by this equation many guys remember Archie over at half is 0 . 0 2 5 6 9 3 bowls by place that in this equation and I can say these cell equals the non-selfie minus 0 . 0 2 5 6 9 3 balls for over 10 times Ellen if you replace all the constant and put the values that correspond those Constance Baker Motley that number and I can replace those numbers that his party over half with that so now let's apply this in a problem OK and so let's take this example for were asked to calculate so calculated the potential at 25 degrees Celsius of Adandia in which the concentration of zinc alliances . 1 0 multiple leaders and added the Cup Orion's is . 0 1 0 0 1 0 moles per liter so we were calculating the standard cell potential we know that's the 1 . 1 0 waltz right and that we can get from the tables of standard reduction potential of we can calculated by the standards cell potential would be the reduction potential at the Catalan plus the reduction you know foot that around and the potential at the end of any sum them up if it's going to be under other conditions there will use the nearest equation so we know that if you have a let's look at what's given to us we know that the concentration of zinc iron is 0 . 1 0 Muller the concentration of copper mines is . 0 0 0 1 0 more and we now but the standards of potential for the Daniel cell is 1 . 1 0 World now what we need to calculate years the cell potential when it's not under standard conditions right and so we know that yeast cell equals the not minus 0 . 0 2 5 6 9 3 Vols divided by an times Ellen I write with which it is not so minus 0 . 0 2 5 6 9 3 holes divided by end and we know Ellen Is the concentrations of the reactants and products and we offer the Daniel sell the reaction that we're looking at is ink solid plus copper to plus requests giving me zinc to plus the quest plus copper solid so the equilibrium expression for the expression of a Q would be the concentration of zinc iron so divided by the concentration of copper ions are that's what he would be and therefore I can say said equals 1 . 1 0 volts which is not sell minus 0 . 0 2 5 6 9 3 walls divided by an and remember any gives you the number of holes electrons are being transferred so how many moles of electrons are transferred and that balanced equation 2 right Olympic 2 there and then there's the the Allen times the concentration of zinc is . 1 0 Moeller divided by . 0 0 1 0 Moeller a right and so on but I'll end up with ECL equals 1 . 1 0 walls minus and if you put all these numbers into the equation and software if it comes out to be 0 . 0 0 5 9 balls and you subtract that it comes out to be plus 1 . 0 4 walls right so you can see the cell when you have 1 molar concentration of zinc and 1 molar concentrations of copper and that's the cell potential staff under standard conditions will be 1 . 1 0 walls but as the reaction proceeds now you can see the cell potential decreases as the concentrations change in both chambers are right and this will be the cell potential when the concentrations are the ones provided there OK so they get a problem where you're asked to calculate the change in cell potential as the reaction proceeds and you know the concentrations in the 2 chambers in the air in the chamber where you have the attitude in the chamber where you have the cathode would now you can affect calculates the self-protection but so that kind of completion looking at galvanic cells and remember galvanic cells to take advantage of a spontaneous reaction OK now we have a look at cells that make use of a non spontaneous reaction and we call this electrolysis or we call them electrolytic cells are right so would you look at electrolytic cells or electrolysis the hit of the and let's just talk about this a little bit so in
so can oversee that I do not know how long I have to keep them into separate chambers I can keep electrodes in the same Chamber because now I have full control of the direction of the reactions are right and the external current is going to force the reaction to go in the direction you wanted to all right and there is no concern about them reacting directly with each other yes yes so you don't find is a little confusing because what I did was I'm taking all right and that and taking the set up and had undoing this year and because we always draw everything with the added on the left side of the the Capitol the rights I do understand that so I took this sound this is where some people get a little confused because reversing the reaction but actually doing as flipping it over because we always keep the animal on the left-hand side in the capital the hand side to see that and so this is what I'm doing all right and I flipped it over so that I could them on the same side because you know that's where the oxidation always takes place but in reality we've actually reversed it all right and we no longer have to keep the 2 chambers separated from each other because we're not taking advantage of spontaneous reactions were actually controlling the direction of electrons flowing were controlling the direction of the electron flow we don't have to keep the 2 two-channel timber separate we do not need a stoppage anymore all right and therefore would you end up with is this drawn here came so you can see that this site will be the copper so the will now be the copper electrodes and the catalog will be the zinc electrode all right and the annual enhanced the oxidation so copper solitude will go to copper to plus plus 2 electrons here where the
oxidation takes place on the reduction side wouldn't have now that the 2 electrons being picked up because that's where the reduction takes place so you have to to zinc to players picking up 2 electrons to give you a zinc solid to see that sells essentially what we've done is we've just drawn but we reverse the 2 electrodes what was and what used to be the zinc now the enters the copper and a cap that used to be copper but now the capital is is zinc that so now if I wanted to calculate the potential for this reaction can only the sign is when we fled all right so what we have is that the all have copper solid going to cover 2 plus 2 plus 2 electrons remember this is the oxidation and therefore if I want write the potential that corresponds to the best I would turn the tables picked the value that corresponds to that because it's an oxidation and underfoot the sign and sign would be a negative 0 . 3 4 vaults right in and galvanic cell this would be the reduction in therefore for the sign would be positive I write the value that you get from the tables of a plus point 3 4 walls but now because this is the oxidation effort sign around now on the side of it by Take the Capital you can see that this is Inc to plus picking up 2 electrons to give using solid the reduction and this is the value that I would take from the tables and in the tables you look at this value this is negative . 7 6 walls all right so far this reaction you can see that copper solid closing 2 plus gives me copper to plus plus zinc solid and you not sell for this would be negative which is negative 1 . 1 0 waltz to see that electrolytic cell your cell potential comes out to be a negative because this is a non spontaneous process which driving using an external voltage that can oversee that have I want this reverse reactions take place I have to supply a minimum of 1 the 1 . 1 0 volts in that direction you see that to be made in minimal amount of external voltage that needs to be supplied to drive reaction in this direction will be 1 . 1 0 walls and everything that but it turned out in practice you have to actually supplied more right so it's not like you have to supply exactly the amount that's required you actually have to supply an extra amount to get the reaction to go and the difference between the US and the actual value that we supply is :colon although potential so it's like you have to apply depending on the substance that makes up that lecturer so it using copper and zinc now each electrode has a value that's available in tables and Minnesota the lights in the nite .period 6 balls all right said you want to get this to go in this direction not only do you need to supply an external source of 1 . 1 0 balls but you may have to supply a little bit extra which is approximate like . 0 6 walls which is called the old potential so you would have supplied this plus the legal potential and so you have to supply something like 1 . 1 6 balls to get the reaction to go in in that direction as an accessory and you can read a textbook and give you like these are standard values over potential standard values that are listed in Tables a textbook has like for platinum if your of the electorate is a platinum they give you what the value is and you can look at different materials and model potential is very different materials in the center where it is is that you have to supply more than what is required is the minimum amount that's required to get it to go in the reverse direction did you guys get it all right so as did another example let's say that we have electrolytic cell and in this electrolytic cell let's say the NO is where now they opted not to issue takes place and you can have too minors give new C O 2 gas plus 2 electrons and if you look at the values for this in the table it's about negative 136 if you have at the cathode you have magnesium you have energy to class 8 quest picking up the 2 electrons to give you magnesium metal and if you look at the tables for this value it set a cap it's where the reduction takes place and its value comes directly from the tables and therefore if you want the whole cell potential for this you added 2 reactions out so you have to see a minus plus energy 2 plus giving used to see and unsealed to gas plus magnesium solid and this will come out to be negative 3 . 7 2 OK so the same underlying principles that we will the galvanic cells applies here but you can see that in each instance here now yourself potentially overall sales potential will have a negative value because it is not spontaneous and so you can now no the minimum amount of voltage that needs to be supplied to drive the reaction in the opposite direction OK now the electrolysis the underlying principle electrolysis or in an electrolytic cells is what is used in the industry call electroplating all of you heard about you know you can buy jewelry that's left to plated so electroplating means that no 1 can make a necklace out of something like mine which is relatively inexpensive and then you take 18 carat gold for for example and you like to play the surface with our right and this is the end like this is how electroplating is done because what you do it this can you see that in this process let's take this 1 what happens is magnesium is being deposited at the Capitol so center where it is if you want electroplating won a magnesium schooling for example you take them as steel or an Iron Spoon and that would be a capital cell that the shape of the spoon is the Catherine that's dipped in the solution and now you supply the appropriate Khan the voltage all right with real potential and you drive the reaction center what happens at 1 and you can see that chlorine gas is being produced supplying us with this command will bubble out at the other end your school given deposit magnesium on and center where he will form it is a thin layer
depositing as aluminum solid city of aluminum oxide dissolved in there and is aluminum oxide is is being deposited as aluminum so I need to know and I need to know it How many electrons are being supplied all right and so can only see that if you look at the if I assigned oxidation numbers can ever say that this is 3 times negative too therefore in each of these aluminum's will be plus
3 you said 6 on the site 6 miners on the side you look at it as what is the oxidation number of aluminum so
can oversee that when aluminum goes 2 aluminum solid How many electrons involved each aluminum Adam Beach aluminum iron goes from plus 3 2 0 all right is that a reduction or oxidation reduction and you know that 3 electrons are being pissed that for each were looking at 1 aluminum iron each aluminum iron will pick up 3 electrons so that means for every mall of aluminum that's deposited it needs 3 malls electrons can the center what's happening is that aluminum 3 three-plus is picking up 3 electrons to give me aluminum solid so we used to this problem in 1 single step operated by 1 0 grams of aluminum deposited when I start with the and current Sino current isn't amperes times the time which was 24 hours I have to give this in seconds I'm going to convert 24 hours 2 seconds and all of
this will come up to me that's a 24 hours per minute you know 60 minutes per hour and the 60 seconds for a minute so that would be the time so this is hereby multiply this by this it qualms and divide by various constant which is 9 . 6 5 times 10 to the book for Kulongoski promote so what I have got this gives me the number of molds of electrons right now I know that this is the number of moles electron in this equation can everybody CA that for every 1 mole of aluminum how many malls of electrons do need 3 OK so that means I can say for everyone mold of aluminum I need 3 moles of electrons all right so what I've got is molds of aluminum them so Kerry said that the 1st step was calculating the number of holes of electrons the number of moles of electrons I know that for every 3 malls electrons is 1 wall of aluminum now and then multiplied by the mall a massive of aluminum which is 26 . 9 8 grams GM from all and so what I end up with is 8 . 0 5 times 10 to the 5 grams of aluminum OK just to keep track of significant figures and since on using everything the 3 6 figs can you change this to 3 significant figures that your answer comes out of the significant figures sorry year and amperes to 6 figs this work out to say things if you make the Triassic things that gives
you the grounds of aluminum that will be deposited right
Besprechung/Interview
Chemische Forschung
Genexpression
Galvanisches Element
Gleichgewichtskonstante
Aktionspotenzial
Krankengeschichte
Biologisches Lebensmittel
Elektron <Legierung>
Reaktionsführung
Graphiteinlagerungsverbindungen
Galvanisches Element
Edelstein
Aktionspotenzial
Körpertemperatur
Gibbs-Energie
Elektronegativität
Alkoholgehalt
Stoffmenge
Gleichgewichtskonstante
Überleben
Elektron <Legierung>
Redoxpotential
Reaktionsführung
Wildbach
Reaktivität
Graphiteinlagerungsverbindungen
Galvanisches Element
Aktionspotenzial
Kupfer
Metallatom
Methyliodid
Konzentrat
Wasser
Druckausgleich
Galvanisches Element
Klinisches Experiment
Aktionspotenzial
Sense
Redoxsystem
Eisenherstellung
Körpertemperatur
Redoxpotential
Molvolumen
Delta
Zunderbeständigkeit
Gleichgewichtskonstante
Primärelement
Reaktionsführung
Zink
Topizität
Genexpression
Brennkammer
Gen
Gibbs-Energie
Chemische Formel
Rückstand
Krankheit
Selbstentzündung
Chemische Forschung
Mineralbildung
Kupfer
Single electron transfer
Zinkoxid
Metallatom
Calciumhydroxid
Konzentrat
Graphiteinlagerungsverbindungen
Disposition <Medizin>
Galvanisches Element
Computeranimation
Alaune
Strom
Aktionspotenzial
Elektrolyse
Sense
Eisenherstellung
Redoxsystem
Redoxpotential
Wildbach
Molvolumen
Alkoholgehalt
Paste
Funktionelle Gruppe
Bäckerhefe
Reglersubstanz
Jukos
Primärelement
Elektron <Legierung>
Reaktionsführung
Korken
Zink
Quellgebiet
Galvanisches Element
Zuchtziel
Durchfluss
Genexpression
Elektrolytlösung
Brennkammer
Azokupplung
CHARGE-Assoziation
Gibbs-Energie
Desublimation
Krankheit
Selbstentzündung
Chemischer Prozess
Kupfer
Graphiteinlagerungsverbindungen
Magnesium
Lösung
Galvanisches Element
Alaune
Werkstoffkunde
Strom
Aktionspotenzial
Elektrolyse
Chlor
Redoxsystem
Eisenherstellung
Oberflächenchemie
Querprofil
Platin
Aktives Zentrum
Reglersubstanz
Tiermodell
Elektron <Legierung>
Stahl
Reaktionsführung
Korken
Zink
Quellgebiet
Gold
Zuchtziel
Durchfluss
Karat
Elektrolytlösung
Brennkammer
Bukett <Wein>
Desublimation
Selbstentzündung
Proteinglutamin-Glutamyltransferase <Proteinglutamin-gamma-glutamyltransferase>
Chemischer Prozess
Periodate
Molekularstrahl
Auftauen
Mil
Metallatom
Calciumhydroxid
Oxide
Eisenerz
Kochsalz
Magnesium
Kryolith
Verschleiß
Lösung
Galvanisches Element
Konkrement <Innere Medizin>
Strom
Werkstoffkunde
Reaktionsgleichung
Aktives Zentrum
Aceton
Elektrolyse
Eisenherstellung
Oberflächenchemie
Verbrennung
Stoffmenge
Elektrolyse
Reglersubstanz
Elektron <Legierung>
Reaktionsführung
Korken
Setzen <Verfahrenstechnik>
Gold
Galvanisches Element
Monozyten-Makrophagen-System
Aluminium
Brandsilber
Einschluss
Elektrolytlösung
Formaldehyd
Toll-like-Rezeptoren
CHARGE-Assoziation
Desublimation
Elektrolytlösung
Aluminium
Chemischer Prozess
Orlistat
Tonerde
Mineralbildung
Auftauen
Oxidationszahl
Elektron <Legierung>
Oxide
Galvanisches Element
Aluminium
Arachidonsäure
Computeranimation
Elektrolytlösung
Elektrolyse
Aluminium
Tonerde
Aktives Zentrum
Auftauen
Elektron <Legierung>
Oxide
Gangart <Erzlagerstätte>
Galvanisches Element
Aluminium
Kryolith
Arachidonsäure
Computeranimation
Strom
Gekochter Schinken
Peroxidase
Redoxsystem
Eisenherstellung
Wildbach
Elektrolytlösung
Stoffmenge
Aluminium
Elektrolyse
Aluminium