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Lecture 16. Electrochemistry Pt. 1.

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prior to looking at extra electric chemistry we want to understand what it means when we say a reaction is an oxidation reduction reaction to those memories that which all reactions can be categorized into 3 groups the 1st group of the acid-base reactions and we look at that in the past we know acid-base reactions involved proton transfer so if you look at a balanced equation and you look at 2 reactants and you see that a Proton is being transferred from 1 to the other then you know that there is a proton donor that's the acid and the substance that accept separate times the proton accepted that will be the base in which you end up with is an asset freeze reaction the 2nd class of reactions that we looked at what the precipitation reactions and we said we use solemnly rules to help us and if you start with 2 substances that are completely soluble combined and you end up with an insoluble substances that that class of reactions are called the precipitation reactions it was the 3rd class of reactions of the oxidation reduction reactions or redox reactions they mean the same thing OK abbreviated form of the oxidation reduction reaction is :colon redox right and these involved electron transfer so in these reactions 1 substance gives off electrons In the other substances picks up that electrons and we end up by having electrons being transferred 1 of electrons are transferred and that is an oxidation reduction reaction but is all you can recognize unlike the previous 2 where you can look at the reactors like input on transfer you can see that the Proton is 1 substance earlier moves to another by looking at the balanced equation it's easy to figure out whether it's an acid-base reaction or precipitation reactions In the case of redox reactions just by looking at a balanced equation it's hard for us to figure out with electrons are being transferred because the balanced equation does not have electrons Is that good and been so the interval look at the equation itself and figure out whether 1 substances losing electrons and with the other substances picking up so we have to have a system of keeping track of electrons recalled that electron counting electron bookkeeping and didn't keep track of electrons that we have to have it easy system or set of rules that we apply to assist us in figuring out the number of electrons and being transferred and the system that we've come up with is called oxidation numbers so 1 way to express the number of electrons lost or gained by a substance in a redox reactions is by assigning an oxidation number to each added so this much like a game you know you might amuse yourself of rules and as long as you stick to the rules everything ,comma works out well the same thing here would have to come up with a system of rules and as long as we stick to those rules then we can figure out whether the electrons having lost a game of is any change in the number of electrons little look at every atom in substance individually to figure out whether there is a change in the number of electrons so that's why an oxidation numbers an oxidation number is number and this number can be 0 positive or negative assigned to each adamant in any substance in oxidation reduction reaction that reflects the will of the Adam has few words it has few electrons in it started as a positive sign it has more the opposition will have a negative side or the same that would be 0 as the number of electrons as an on combined neutral-and so business at its oxygen numbers is just the way it for us to keep track of electron a and so on oxidation number can be positive or negative 0 0 OK and we you Arabic numbers you know that the numbers of the 1 2 3 that we usually using the online homework it'll say give your answered in Arabic numbers that means that we were using anonymously that we can also sign oxidation states and for that we use Roman numerals to distinguish between the 2 so right now now we're looking at oxidation numbers and would use Arabic numbers of tanks so so if you look at the class website put the rules out on the class
website and these are the rules for signing oxidation numbers from before I start usually like soluble the rules case a value stuff like that I will provide on the example of this I will not give to you because this is something that you need to understand internalized and be able to use their intuitively and sell these rules you need to understand them and be able to apply them in these rules will not be provided on an example of solar cell with the first one and oxidation number every element in its natural state is 0 so if you take sodium it is natural state its metallic sodium sentimental itself it will have 0 you take metallic silver that's how the element exists in its natural state it'll be 0 if you take America in the liquid stated the mercury as all of you now it's a natural state that will have an oxidation numbers 0 oxygen in its elemental state exists as all to H 2 in examined state exists Haydn exist H 2 chlorine exists a C O 2 so as long as the Ellen it existed its elemental state it has an oxidation state of 0 OK the 2nd is the oxidation number of Vermont atomic kind is the same as it signed shops Evitts a cat I know and I know it's model cabinet and beneath oxidation number corresponds to the charge and so in plus would be plus 1 seal minus 181 if the 2 plus 2 plus 2 F minus will be megawatts opposition number corresponds to the charges the 3rd when we deal with oxygen OK in most compounds containing oxygen the oxidation number of oxygen is needed to send it all to oxygen elemental state of the 0 but if oxygen is found in a substance then the common state is that it has a minus to oxidation numbers if you take magnesium oxide it has naked to so too is native to SO 3 negative C O C O 2 in formula where the common form is where it has oxidation number of negative to the only exception is other peroxides approximate the pretty rare and a peroxide is able to to minors so there to oxygen an overall it has a 2 -minus charge so if you take there to oxygen to have all brought to mind is charged with the charred each oxygen minus 1 right and that's why you take exception to the rule of the prop sites in which the oxidation number has a minus 1 of K cake hardly tell proxied look at the formula designed H 2 0 2 orgy of a medal like in the 2 0 0 2 or write a look at the charge that they you take any tool to you conceded to many classes so that means a World War Two mostly to minus therefore each oxygen has to be minus 1 K but peroxides not very common the most common wanted an on the ones that have minus to gained the 4th rule is that in most compounds containing hydrogen oxidation number of hydrogen is plus 1 the date C & H 3 h dual CH for these all have plus 1 the exception to this rule other metal hydride in which the hydrogen has an oxidation number of negative want to know if you have like lithium sodium potassium and metal with a hydrogen then it's a metal hydride or rights you have a metal attached to hydrogen the metal hydride and its oxidation number would be negative 1 now last is that this summer Of the oxidation numbers must be 0 for electrically neutral compounds for Polly atomic lines this summer the oxidation numbers was equal to the charge of the I'm signing oxidation numbers for every atom in a substance so you added the the oxidation numbers if its electrical neutral compound like water has no charge on that means when you add up all the opposition numbers of you have got such numbers for the 2 hydrogen and oxygen number for that 1 oxygen and together it needs to add up to 0 because it is charged in these across find the charts of Uday Chromium the oxidation of chromium plus the opposition Democrats wonderful oxygen you add the amount they have equal needed to and if you take in each for you take nitrogen and had the oxygen member of this To that station reported these missions that with a plus 1 solution state a number of the Secretary General is applied this but because of users often to figure out where the company's losing electrons of gaining chance so we'll start by by taking an example where you're asked to calculate the opposition numbers so what's out with a simple 1 calculate the oxidation numbers for carbon in C O 2 all right so you started point would be to take the compound and we know that overall this election "quotation mark neutral compounds so that some of the oxidation numbers corresponding to the to the Adams should at 2 0 2 since we need to find oxidation number for carbon were going to say we're going to call that and
we have to oxygen is sold 2 times what is it won't tell us what is the oxidation number of oxygen needed to be alright so this will be negative too so we know that some of these 2 should correspond to the overall charge of the molecule so we know and plus 2 -minus 2 should equal 0 therefore any equality Class 4 so the oxidation number that corresponds that Coburn will be be 4 we always assigned oxidation numbers per 1 Adam are right so we have better without their 2 oxygen stare each oxygen individually has an opposition member of negative to him because if 2 of those have multiplied by 2 OK so this is another example line HT fuel for select saying calculate the oxidation number for phosphorus in 83 appeal for so once again we have reached 3 fuel for the 1 that we need to figure out what college and we have hydrogen and we have oxygen right we have 3 be hydrogen is and what is that will tell us that the opposition number for hydrogen and plus 1 right this will be there for oxygen is each oxygen we know from the rules will have a negative 2 so that is the sum of all of this should equal the overall charge so we know that 3 times plus 1 plus and plus 4 times negative too she equals 0 therefore and should be called 8 minus 3 which is plus 5 to the oxidation number for phosphorus in that ,comma ground is plus 5 natural I need you to be able to do this ,comma mentally in your head and quickly capillaries but for now will go through the details OK now let's take a good example calculating the oxidation number for chlorine in sealed 3 -minus OK so once again if you take this formula this is what we need to find a similar call that and you can see that the other component is 3 so we know that each oxygen is negative too yet 3 of those that will be connected to the nite considers poly atomic line that has attracted negative ones so that the sum of the sitution equal negative 1 so that means plus 3 times negative too should equal negative ones therefore equals 6 minus 1 of which is plus 5 all right and so once again you can see that when you assign oxidation numbers you have to put signs in India has 7 inside and find if it's a number of positive sign for Hassan's 0 against no last listed something life prior sulfate which is S 2 and 3 so calculate the oxidation number for Salford in this 2 or 3 to minus right so no remember oxidation numbers are always assigned per 1 added so that truce offers so many say to and right and their 3 oxygen is and we know from the rules the oxygen has an to oxidation number so that some of these 2 should he fall to minus right so we know to and plus 3 times negative too should equal negative too which is the overall charge therefore to N equals 6 miners to which is plus 4 and we always assign oxidation numbers per individual Adam so each South for Adams will have plus 2 divided by 2 each added has just gotten so like any formula that we should be able to figure out what the oxidation number for all the elements are usually most comprehensive deal with have hydrogen iodide oxygen on it so we used that those elements to figure out what the oxygen number for the other 1 is you have cancer and you know that they correspond to the charge monotonic and my new on Monday ,comma candidates monotonic and fines for corresponds to the charges well take that supply this In an example what we're looking at a redox reactions so it might take a redox reaction and we said and redox reaction involves electron transfer case so let's just take an example where we have to move reactants and let's say in this reaction a transfers 1 electron to be alright said 88 transfers 1 electron to be there were to end up with is it has lost electrons to be a plus plus B -minus all right so you have something there that you can direct the seed electrons being transferred sometime that 1 electron is being transferred all right now when we look at the docks reactions as electron transfer and a convenient way to kind of look at what's going on is to look at what we call half reactions are so it might take half reactions you can see that goes to aid last plus an electron In this case we right have reacted you can see that when a goes to a plus it's losing 1 electron occasion whenever bounced equations remember you have to maintain charge balance so begin on the inside everything is electrically neutral you end up in a plus so the balance that charges you can figure how many electron to balance that shocked see it
fosters needs 1 electron to bounce the charge in you know 1 electron has given up right now on the other so we called them the oxidation half reaction member Wise's their hot oxidation have reaction because oxidation is Electron lost and Larsen will look at the definition of oxidation oxidation it involves the loss of electrons wins a substance loses electrons colored oxidation when a substance picks up electrons which we call that a reduction so now oxidation reduction reactions we said last time have to go hand in hand you can't have 1 without the other it's something gives of electrons something has to pick it up so you need both of those components are right so you can have 1 substance giving a lecture on the rules electron the sitting out there in the are right can never have electrons just sitting in Kenya near if 1 is giving off another substance used to take it and they need to take place at the same time and so if you look at the reduction have reaction now this electron that's given our is pick baby any goes to B-minus once again charged that once you have a neutral -minus once on this said minus when charge if on this side I have to have a minds when charges were up this is called the reduction half reaction why this is where electron gain workers are right now I want to remind you that you know we write half reactions because it convenient for us to kind of rationalize what's going on in reality reactions don't take place in half reactions Duras and because the incident electron given all the others taken up and so you don't have this process where 1 electron comes out in other lecturers and picked up its immediately transferred from 1 to the other Sony oxygen reduction reactivated take place instantaneously and you don't have half reactions occurring but have reacted purely a mental process for us to kind separated out to understand what is going on said so if if I want to make a little table I can't say that might take so let's combined let's look at what happens at 88 and when it happens the members we have to look at the reactants arrive so you can see gate loses electrons in other than losing 1 electron 1 or more electron so it loses electrons B James electrons right AAA undergoes oxidation for it is oxidized and we said the undergoes a reduction for it is produced all right now last time we looked at we you get redox reactions you need to be able to identify what is undergoing oxidation or what is being oxidized what is undergoing reduction in what is being reduced arrived the next possession into now which is the alright so since this is undergoing oxidation and this is that it is reducing agent this is the age and that's responsible for reducing the substance which is undergoing a reduction and is a oxidizing agent all right whenever a substance undergoes oxidation the oxidation number increases so the oxidation number of these increases all right so the oxidation number of aid increases and if it's undergoing a reduction in the oxidation number of B decreases so this important points to remember you're looking at the oxidation reduction reaction I need you to be able to look at each 1 of these and Theobald identified for each reactor and need to know which 1 is losing electrons to figure out which is gaining lecture you need to figure out which 1 is being oxidized which is being reduced the need to figure out which is the oxidizing agent which is a reducing agent whenever you have an oxidation the oxidation of increases are right when the substance loses electrons it's oxidation number increases when a substance gains electrons its oxidation number decreases so it oxidation reduction reaction at the oxidation number changes you know that oxidation reduction reaction 1 substance oxygen will go up that means it's oxidized and another substance oxygen number will decrease that's the 1 that's being reduced caseloads take example and what stop simple examples more complicated ones so let's take some examples In the 1st example undertaking is where you have potassium solid and if so this is metallic potassium reacting with chlorine gas to give you an ionic compounds which is potassium chloride so quickly checked with this equation is bouncier 2 potassium stupid shift to to now the unit cigarette out with the redox reactions are not we have to look at oxidation numbers OK so to begin with we always look at it per 1 are right so in this there 2 potassium in last equation and so by take potassium this is an element in its natural state therefore it's oxidation number has to be 0 and there to coefficient the coefficients outside game over here
chlorine in there to chlorine atoms but this is an element in its natural state therefore the oxidation state of the 2 chlorine atoms and C to each 1 will have an opposition number of 0 OK so that the 2 times 0 ppm no on this side we end up with an ionic compounds are right this is a metal nonmetal combination it's an ionic company and we have to have a cat I'm and Indiana so by take the potassium you can see that that's K plus therefore each potassium will have a plus-one In each chlorine will have a minus 1 so what's outside is the questions the balanced equation of the number of Adams that's in there in the balanced equation appear to now we have to look at this equation and we want figure out this oxidation numbers changed the look of potassium each potassium Adam goes from 0 2 plus 1 so is there a change yes now you ask itself so that the redox reactions secondly the oxidation of increasing or decreasing so the did potassium egos and 0 2 plus 1 so increases remember it the oxidation of increases what is that the oxidation alright so we we start looking at the 2 reactants as saying that wind goes to that oxidation number increases and we know that's an oxidation and by how much does it change goes each 1 goes from 0 to negative 1 so that means that if there is a change by 1 I write it goes from 0 to class when that if there's a change of 1 that means 1 electron is being transferred but there to Adams so overall see to electronics have been transferred overall 2 electrons are transferred as each potassium atoms goes from an oxidation number of 0 2 plus 1 is net change of 1 the net change of 1 means that 1 electron is being lost but overall we have to see multiplied by 2 and so in this reaction to electrons are being lost right now if you go to know what's being reduced over here now you chlorine the Likud opposition but because 0 2 negative 1 so you know that oxidation number decreases and if it decreases as it means it's a reduction did each chlorine atom and it changes by 1 of so since the since electrons of being lost and would bring negative here to show me that electrons being lost Oregon native assignments electrons are lost positive signs mean electrons being game to be looked at this beach chlorine atom goes from 0 to negative 1 sits in a change of 1 so it decreases by once and then say 1 electron but since there are 2 Adams involved altogether 2 electrons are being lost so we figured out from this by looking at oxidation numbers that 2 electrons are lost and 2 electrons and gain right now the cardinal rule it is that the number of electrons given not have to equal the number of electrons taken up it doesn't work out you know there's something wrong with that we our the rationale duration and that because you can't have 10 electrons do not vilified taken up all right the number of electrons given not always have to equal the number of electrons take enough already indecency to electrons are given our 2 electrons picked that now so what is undergoing observation potassium this is oxidized you can see chlorine is reduced I right so the substance being oxidises potassium because it's undergoing oxidation that substance being reduced its chlorine because its oxidation number goes down so that there there substance being reduced if this is being oxidized This is the reducing agent and is the oxidizing agents and we know overall 2 electrons are transferred the all right so it's very important that you every example that you look at you have to be go to this process you gotta figure out what's being oxidized what's being reduced ,comma electrons have been transferred and make use of oxidation numbers to do that it does take another example for a look at the combustion of methane so what happens if you burn methane and oxygen now combustion reaction is also an oxidation reduction reaction so if I take met plus 2 0 0 2 yes giving me carbon-dioxide plus 2 the case of looking at the combustion of methane make sure the equation is balance you can see there's 1 common carbon for hydrogen for hydrogen for oxygen is 2 plus 2 for oxygen again so I can't tell you ahead of time that is the redox reactions a Case of You take a redox reaction I got a figure out what's being oxidized what's being reduced ,comma electrons of being transferred again so the common now by by now you should be able to do this when the facts behind the tap class won the 400 in the plus 1 so what's the opposition of Coburn needed for gate the take hydrogen there 4 times plus 1 that would be the oxygen number assigned to each of the hydrogen each oxygen can you see that there 2 oxygen she times to therefore oxygen against it's an element in its natural state each oxygen atom will be 0 OK now cover the figure out adults opposition stated of Discovery's returned oxygen number each oxygen atom has what is the oxygen number negative too so there is negative 2 times 2 give me negative for so the boxing is negative for the whole companies like the neutral what is the oxygen number of carbon over here plus 4 OK and we are there to oxygen so that's communicated to Nova here we
have hydrogen each hydrogen is plus 1 how many hydrogen do I have to tends to 4 and if I take the oxygen 2 oxygen is and I know that's negative to the members have assigned oxidation numbers for all of the and now I look at 1 better time and figure out which ones are undergoing changes so sell company starts from negative for 2 plus 4 if you are right so that's 1 now this hybrid in change the and share plus 1 of the and plus once a hydrogen does not change but said that oxygen oxygen goes from 0 2 negative to overhear a negative over there to see them so that means of oxygen is changing and it's changing both sets of oxygen is undergoing a change again so let's start with carbon now look at the oxidation number Coburn is that increase or decrease it increases goes from negative for 2 plus 4 so since oxidation number increases waterway known visitors the oxidation and methane is being oxidized right now look at my howling doesn't change member there's 1 carbon atom at the beginning 1 Covenant and so from negative for two-plus for what is the change 8 so that these are electrons involved are right and so this is oxidation like transit mingle lost so we know that there are 8 electrons involves overall 8 electrons have been transferred OK now called to the oxygen side it goes from 0 . 2 negative to as the oxidation of increased or decreased it decreases member of the opposition number decrease as we call that process reduction a now that the harmony oxygen atoms there are there is to 2 times to for oxygen atoms there's 2 plus 2 for oxygen atoms are therefore oxygen atoms and oxen and goes from 0 to negative attitude so what is the change 2 electrons it's a reduction of electrons picked up on electrons lost picked so you know that there are are times plus 2 which gives me plus 8 electrons so how many electrons are being transferred here 8 electrons so in this oxidation reduction reactions you can see that the substance that's undergoing oxidation is methane so that's being oxidized the substance being reduced over here is oxygen all right so this is being oxidized this would be the reducing agent if this is being reduced that would be the oxidizing agent and how many electrons that transfers 8 electrons are transferred OK I need you guys to be able to do this in you sleep OK because if you can figure out how many electrons have been transferred then the whole exercise is a waste of time and you get itself and later on we elect electric chemistry I need you to be just look reaction figure it out and no harm electrons have been transferred to to evict stylistic another example where am let's say I have inside sealed for plus let's say that's liquid plus 2 new H 2 0 liquid gives me for 8 Cl it costs plus side to solid OK so once again let's take a look at this and now we can go pretty fast therefore chlorine each chlorine has minus 1 so what is the oxygen state of silicon plus for therefore chlorides In each 1
is negative 1 because Member chlorine still minors as a negative 1 oxygen number here there are 4 hydrogen is the chided in plus 1 there 2 oxygen and each oxygen will be negative too now on the product side we have for hydrogen so the 4 times plus 1 and therefore chlorides 4 times negative 1 it might take Silicon over here you can see it's plus 4 this is 2 times negative too non-standard move pretty fast because that that's sort of the pace at which you need to be with analyzes reactions cake now look at this and tell me anything undergoing change must open so it is possible that accession numbers plus and the in the reactor plus for the SEC changed not whether that chlorine each chlorine atom to begin with his negative 1 on the product side each scoring this nigger wonders that change not turned to what the title plus 1 on the product side the 100 is plus 1 and oxygen the dioxin is native to the Parkside jocks is negative to sell do oxidation numbers change here not there no changes so is this a redox reactions no but it is no electron transfer all right so reaction is there's no it has to be the acid presentation oxidation reduction reaction look at the hydrogen atom TCU hydrogen atoms move from 1 to the other where decided to start with water it is a hydrogen moving away from waters it's staying together with water city as a proton transfer their proton transfers taking place his approach on transport ,comma reactions that pacifist obtain itself so this is not a redox reactions Synod reaction that you look at what has to be read and with figured out is to look for opposition numbers and with his change obtained so now only to look at something that's very very important and that is balancing the oxidation reduction reactions right no up to this point said review 1 example solicited an example and let's say you want to balance the equation copper plus the Channel 3 giving you copper nitrate the plus With nitrogen plus of H 2 0 4 now it turns out that up to this point if you want a balance the chemical equation all right you only looked at trying to balance Adams are right and you you pretty well versed at balancing equations but it turns out that there is a class of oxidation reduction reactions that are virtually impossible to balance all right and this is 1 such example said you want to use on the general form that views in the past remember usually we say when you bounce equations the number of Adams at the beginning should equal the number adding to the end and you just play around with this and there's no hard and fast rule on how to balance it turned out be tried about this equation you can work on it for a month and analysts who follow a general strategy will not be able to balance equation are right and so these are challenged the equations to balance and the reason is that of that you have be the redox reactions and immediately actors a balance redox reactions the underlying principle that anyone remember is the number of electrons given off half to equal the number of electrons to taken up OK so that's going to the underlying principle so if you are 1 analysis equation and the right amount so that it's it's in 1 line because so we have the 1003 giving you copper nitrate plus in 0 2 plus inched toward the 1st that is willing to sign oxidation numbers OK you have to be a lot about this equation you have to sign oxidation numbers sounded dubious faster 0 he chided plus 1 each oxygen will be 3 times negative to arrive so can you do this this'll be 6 is a big plus 1 selection nitrogen come out to be plus 5 each copper
this is copper two-plus because they're too nitrates a united opposition number copper is costume and therefore you can see the charges to oxygen embraced to each nitrogen there to nitrogen each nitrogen will be plus 5 each oxygen there 6 accidents will be negative too now we here
I have 1 nitrogen What is the oxidation number for that nitrogen plus 4 because they're 2 oxygen is over here am I going to fast I need to work at this pace of his itself people complain that they don't have time and exam I have not mastered the skill or haven't practiced enough to be able to do it kind intuitively so Water is there to Haydn's each had his plus 1 and is this area remain so and that is that is assigned oxygen numbers for all the elements of pain now my next step is to figure out which ones are undergoing changes are right so what is the first one that undergoes a change copper are you what those changes nitrogen McKinney stayed that the mentioned this kind of tricky because some of the nitrogen don't change and some of them do change to see that this is why this equation is so hard to balance because can you see there in all 3 Roma and altering the nitrogen here has a plus 5 oxidation state some of them remained hospitalized and some of them a plus for our rights and therefore we need to figure out how many of these actually change and how many of those nitrogen don't change at all so what is the underlying principle the number of electrons transferred it has to be the same as the number of electrons given off has to be the same as the number of electrons taken up to now the stranded that's you take each copper copper goes from 0 2 plus 2 Is the oxidation number increasing or decreasing increasing amid increased as what we know it's an oxidation and copper changes from 0 2 plus 2 therefore to electrons are lost all right so if 2 electrons are lost ,comma electrons need to be taken up so we don't hear it goes from plus 5 2 plus 4 you see that so that means this is the reduction and we know that each nitrogen goes from plus 5 2 plus 4 so that decreases that's quite reduction promised by how much does it change by 1 so I know that each nitrogen is picking up 1 electron if I want to make is equal to each other I have to multiplied by 2 so that 2 electrons picked up all right so that means that I have to have 2 nitrogen is here to see that because 2 of these are the ones that are being reduced a cake so now let's go back to equation I have copper 1 copper 1 copper so I can't change that now because if I doubled its bite to them for electrons when given up some restricted to electrons being given out I can't change that now I have to an ode to that you change but remember there too in 0 3 there to 906 here that don't change so what is the number needed to put here he said to put forward their because 2 I could to hit a bouncer to electrons so I have to nitrogen sources here plus there to hear so this issue does this to use me for nitrogen is on the side so I have to nitrogen atoms coming from here to nitrogen atoms coming from here or overall I should have for nitrogen atoms on the site to did that once you get back equations balanced otherwise it is trying to add balance to be sitting there for days and you will not be able to figure it out you do it's purely by chance all right just pure luck that he got OK so once you figure that out now I can go back and say so I have full height against their to waters on this side of now let's make sure equation balanced right and I would not confirm I have 1 copper 1 copper I have for hydrogen is I have 2 times to 4 hydrogen so that its goal to oxygen so I O nitrogen cited for nitrogen here so I thought I is here I have to nitrogen and to hear for nitrogen now lets me do the match for oxygen 4 times previously 12 oxygen it's alright so here I have 2 times 3 gives me 6 plus 10 plus 212 so I know all my oxygen is a balanced and I know now I balanced equation to Dubai's get that and sold this way you can balance the equation by looking at oxidation numbers obtained for discussion next week I will give you lots of examples to practice not within the last 3 minutes I moved to another example and and so we still have 3 minutes so if I have been this is my bounced equation in ACL plus H 2 vessels 4 plus a to giving me mn 2 cancel floor plus mn C 2 plus speaks to bowl plus C 2 playing on this question comes directly from an exam that idea 2 years ago right Sanders pulling an old exam questions and you asked to balance this equation all right if you were trying to balance this
aquarium lies the methods that that you've used before which is just looking at AT balance you would not be able to balance this equation all right so it's a redox reaction I have to figure answers equation by looking at the number of electrons given and the number of electrons taken up so quickly and in a sign of oxidation numbers plus 1 -minus 1 2 times plus 1 this will be a negative 2 times for so remember this is 8 minus 2 plus so this has to be plus 6 right now look at manganese is the transition metals to better align oxygen oxygen is 2 times needed to for each manganese will be for on this side I have to manganese so 2 times now the sulfate is for away at my follows wrong wooded area of this should be an ancient story characters the charge bounced itself and act covered is wrong think so there to sodium each 1 is plus 1 each oxygen is negative 2 times 2 each self-rule plus 6 over here each chloride is 2 times negative 1 so this be plus 2 this'll be plus 1 times too negative too 0 Over here we hear yes thank you right now I I need to figure out what is undergoing changes are right so it was plus 1 sodium is lost once a sudden change take chloride is negative 1 goes to 0 so we know chlorine has changed but there are 2 types of chlorine some points that don't change and some that do and the other thing that changes is manganese goes from plus 4 2 plus 2 alright so let's start with manganese singles from plus 4 2 plus 2 is that oxidation that reduction increases and decreases so the decreases it's a
reduction How many electrons are being as if it's a reduction gains electrons those for close to 2 electrons picked that now Kerkorian each chlorine goes from negative 1 2 0 0 6 increasing so that means that an oxidation and it increases by 1 so that means that 1 electron is being kicked out lost answered 1 electron is being lost netted balance this I need to send a multiply that by 2 so that means I need to Florence on this side survived 2 glorious on side 2 0 then undergo a change that is to that don't change somehow interpret here 4 right because there 2 Florence that goal from negative 1 2 0 and 2 . cycle from negative 1 2 negative ones all right so I need for any once I got that now I denied sodium so Simon put to Sudan's there now if you look at the solvated I have 2 entities of the sulfates I need to solve until we hear now I for hydrogen is so I need for hydrogen so we here and a migrations that I will repeat his example I wanted to take a look at his example at home and think about it I will repeat this example at the beginning of class next time angle to this once again because if there is 1 that you understand how to balance redox reactions of
Chemische Forschung
Gummi arabicum
Elektronendonator
Single electron transfer
Memory-Effekt
Erstarrung
Besprechung/Interview
Reaktionsgleichung
Atom
Redoxsystem
Säure
Elektronentransfer
Paste
Funktionelle Gruppe
Systemische Therapie <Pharmakologie>
Oxidationszahl
Aktivierung <Physiologie>
Elektron <Legierung>
Reaktionsführung
Oxidschicht
Niederschlag <Chemie>
Chemischer Reaktor
Tank
Base
Protonierung
Thermoformen
Multiple chemical sensitivity
Adamantan
Sauerstoffverbindungen
Metallatom
Pegelstand
Wasser
Stickstoff
Computeranimation
Domäne <Biochemie>
Atom
Chlor
Redoxsystem
Weinkrankheit
Molekül
Kalium
Phosphor
Elektron <Legierung>
Fülle <Speise>
Reaktionsführung
Hydride
Krebs <Medizin>
Oxidschicht
Quecksilberhalogenide
Ordnungszahl
Brandsilber
Peroxide
Ionenbindung
Iodwasserstoff
Metall
Thermoformen
Metallhydride
Chemische Verbindungen
Mineralbildung
Chlorwasserstoff
Chemisches Element
Kohlenstofffaser
Benzodiazepine
Hydride
Magnesiumoxid
Chemische Verbindungen
Lösung
Reaktionsgleichung
Werkzeugstahl
Elektronegativität
Dachschiefer
Elektronentransfer
Chrom
Aktives Zentrum
Oxidationszahl
Neutralisation <Chemie>
Tiermodell
Hydrierung
Schönen
Quellgebiet
Natrium
Katalase
CHARGE-Assoziation
Wasserstoff
Anomalie <Medizin>
Chemische Formel
Lithium
Cupcake
Sauerstoffverbindungen
Chemisches Element
Redoxsystem
Adamantan
Sauerstoffverbindungen
Methanisierung
Metallatom
Kohlenstofffaser
Carboniumion
Brennbarkeit
Nichtmetallverbindungen
Oxidans
Nahtoderfahrung
Chemische Verbindungen
Computeranimation
Reaktionsgleichung
Atom
Altern
Chlor
Reduktionsmittel
Redoxsystem
Kaliumchlorid
Antigen
Allmende
Zigarette
Kalium
Oxidationszahl
Hydrierung
Elektron <Legierung>
Reaktionsführung
Oxidschicht
Famotidin
Mähdrescher
Ordnungszahl
Katalase
CHARGE-Assoziation
Komplikation
Chemisches Element
Quantenchemie
Chemischer Prozess
Sauerstoffverbindungen
Methanisierung
Chemische Forschung
Kupfer
Stereoselektivität
Single electron transfer
Kohlenstofffaser
Wasser
Disposition <Medizin>
Stickstoff
Computeranimation
Reaktionsgleichung
Atom
Chlor
Ionenkanal
Reduktionsmittel
Redoxsystem
Simulation <Medizin>
Übergangsmetall
Säure
Elektronentransfer
Transport
Hybridisierung <Chemie>
Dioxine
Oxidationszahl
Hydrierung
Elektron <Legierung>
Molekülbibliothek
Reaktionsführung
Oxidschicht
Chemieingenieurin
Silicone
Chloridion
Protonierung
Nitrate
Thermoformen
Cupcake
Verletzung
Kohlenstoffatom
Chemischer Prozess
Sauerstoffverbindungen
Kupfer
Chemische Forschung
Wasser
Stickstoff
Computeranimation
Reaktionsgleichung
Reduktionsmittel
Zündholz
Aktives Zentrum
Oxidationszahl
Hydrierung
Elektron <Legierung>
Oxidschicht
Querprofil
Quellgebiet
Gangart <Erzlagerstätte>
Ordnungszahl
CHARGE-Assoziation
Schmerz
Cupcake
Titan
Chemisches Element
Advanced glycosylation end products
Valin
Hydroxybuttersäure <gamma->
Sauerstoffverbindungen
Ader <Geologie>
Chloride
Oxidationszahl
Hydrierung
Elektron <Legierung>
Oxidschicht
Querprofil
Setzen <Verfahrenstechnik>
Magnetometer
Natrium
Computeranimation
Reaktionsgleichung
Chlor
CHARGE-Assoziation
Reduktionsmittel
Redoxsystem
Bukett <Wein>
Übergangsmetall
Sulfate
Alignment <Biochemie>
Zellmigration
Manganerz
Sauerstoffverbindungen

Metadaten

Formale Metadaten

Titel Lecture 16. Electrochemistry Pt. 1.
Serientitel Chemistry 1C: General Chemistry
Teil 16
Anzahl der Teile 26
Autor Arasasingham, Ramesh D.
Lizenz CC-Namensnennung - Weitergabe unter gleichen Bedingungen 3.0 USA:
Sie dürfen das Werk bzw. den Inhalt zu jedem legalen Zweck nutzen, verändern und in unveränderter oder veränderter Form vervielfältigen, verbreiten und öffentlich zugänglich machen, sofern Sie den Namen des Autors/Rechteinhabers in der von ihm festgelegten Weise nennen und das Werk bzw. diesen Inhalt auch in veränderter Form nur unter den Bedingungen dieser Lizenz weitergeben.
DOI 10.5446/19005
Herausgeber University of California Irvine (UCI)
Erscheinungsjahr 2013
Sprache Englisch

Inhaltliche Metadaten

Fachgebiet Chemie
Abstract UCI Chem 1C General Chemistry (Spring 2013) Lec 16. General Chemistry -- Electrochemistry -- Part 1 Instructor: Ramesh D. Arasasingham, Ph.D. Description: UCI Chem 1C is the third and final quarter of General Chemistry series and covers the following topics: equilibria, aqueous acid-base equilibria, solubility equilibria, oxidation reduction reactions, electrochemistry; kinetics; special topics. Index of Topics: 0:00:00 Oxidation Reduction Reaction Review 0:02:55 Oxidation Numbers 0:04:50 Rules for Assigning Oxidation Numbers 0:10:13 Calculating Oxidation Number Example 0:16:26 Redox Reactions 0:17:10 Half Reactions 0:23:09 Example of Redox Reactions 0:37:58 Balancing Oxidation-Reduction Reactions 0:47:04 Challenging Redox Question

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