wanna do is I want to do some redox stuff now [Music] on Monday we're going to review the organic chemistry test okay let's take a look we started redox with our understanding of oxidation numbers there's some rules that we have to know for oxidation numbers and I tried to boil it down as much as I could I tried to just boil it down to four rules okay it's it's more complicated than that but for the most part elements are always what what do they always have an oxidation around zero right and the reason why that is is chlorine as this that's more-- there we go and the chlorine has this okay can you kind of see how each chlorine brings an electron to the table for this bond now the oxidation numbers are basically saying compared to the atom compared to this normal atom does this app does this substance this thing is it kind of stealing more than its fair share of electrons or is it giving away more than its fair share of electrons now it doesn't matter what the electronegativity of a substance is if it's a pure if it's an element like chlorine what's the electronegativity of chlorine no no not to charge 3.2 okay 3.2 is pretty high electronegativity its electronegativity shows how hard it's pulling on electrons in the bond but when this guy's electronegativities 3.2 and this guy's electronegativities 3.2 who's pulling harder on those electrons nobody doesn't matter how hard you pull if you're pulling on equal strengths right so who is winning the battle for these electrons nobody so their oxidation number is zero note there they haven't gained any electrons they haven't lost any electrons compared to the atomic level like that it's okay oxygen in a compound we always give it an oxidation number of what - - and that's because oxygen often makes two bonds with things so it'll steal an electron from this guy and steal electron from that guy right the only kind of little subtle difference is when you have a peroxide and that's two oxygens back to back so is the oxygen stealing the electron away from that oxygen no so it only has one bond to steal from so that's why peroxides we say the oxygens minus one now you didn't see a single example of peroxides in the entirety of this unit and I really really really suspect you will not see it on the Diploma exam day but I just have to say it just because it's Mac's question yeah but that's not that's not an O oh it's an O bonded to an O so it's different from this this is COOH yeah that's the only peroxide that I think you could ever see that's and even then hydrogen peroxide is in our table of half-reactions so probably you'll never have to deal with it okay I just I just want to say that okay hydrogen's in a compound are always what +1 right the total sum the total sum of all the oxidation numbers in a thing in an entity must equal the charge on that substance so if a substance is neutrally charged like in ch4 what do all the oxidation numbers have to add up to be zero zero but if they're like I Oh three - what are they all have to add up to be minus one so what I want you to do do you want me to recap this with you no okay you I'm gonna give you 30 seconds to a minute to try and figure out as many of these as you can and then I'm gonna write down what they are you gonna do this you're gonna test okay it seems like most people are kind of close to being done so say the oxygen is negative 2 and ayah dates so negative 6 and we don't want to get rid of all the negative sticks - this has to be plus 5 did you get plus 5 for iodine yeah okay good the co2 so that's minus 2 there's two of them so that's going to be plus 4 so the coppers plus their carbon is plus 4 the hydrogen's are plus 1 that means the carbon has to be minus 4 and then there's four oxygens there each minus two that's minus eight we don't want to cancel out all eight when I want to cancel out seven out of the Aces gotta be plus eleven so those are the those in the oxidation states or oxidation numbers for these elements and these entities any questions about that cool oxidation reduction or redox reactions must involve a transfer of electrons this is so important if something's gaining electrons something else has to be losing electrons right so if you if you draw two half reactions right if you write up two half reactions did you say bla bla bla plus electrons gives you a blob of block and then it in your other half reaction if you say bla bla bla plus two electrons gives you bla bla bla is the do those two half reactions make sense are they reacting with each other no they can't be reacting with each other you can't have both things give away electrons and nothing gained you can't have both things gain electrons and have nothing give away electrons does that make sense something has to be a reduction and something has to be an oxidation reaction so identify the following reactions as redox or not redox reactions if it is redox identify the substance being oxidized substance being reduced so stressed how are you gonna tell if something is being oxidized or reduced oxidation numbers is probably the best thing to identify and if you're oxidation number changes at all then you can be pretty sure it's a redox reaction do any of the oxidation numbers in this first equation change yes no they don't okay so let's let's try and prove that to ourselves nh3 what's the only oxidation state you know for sure in nh3 is plus one so three of them right that means minus three so let's see if nitrogen changes let's go over here this is plus one and there's four of them but do we want to cancel out all four positive charges no we only want to cancel out three of them so this is still minus three so that hasn't changed this is negative two and plus one that adds up to be zero right this is plus one and that's negative two that adds up to be negative one none of these numbers change this is not a redox reaction right I'll give you a hint acid-base reactions are not redox reactions double replacement reactions are not redox reactions single replacement reactions are okay and combustion reactions are so we need to take a look at the second one is this a redox reaction yes yes 100% how do you know immediately this is zero it changes into minus 2 and minus 2 boobs straight out of the gate straight out of the gate we immediately know that this is a redox reaction something changed now did the oxygen gain or lose electrons it became more negative so it gained right so this thing gained electrons what does that mean was the oxygen reduced or was the oxygen oxidized reduce yeah I mean ger Cola right but but we don't really care about the color right now we're just looking at dirt so gain electrons is reduction absolutely this thing is being reduced okay if this thing's being reduced without doing any more work what's being oxidized another one down yeah this has to be oxidized let's prove it to ourselves the hydrogen's plus one the nitrogen is minus three what's the nitrogen over here it's plus four did the nitrogen lose electrons okay are we okay with that yeah give which what's things being oxidized what things being reduced um if this thing is being oxidized is it acting as the oxidizing agent no if it's being oxidized it's acting as the reducing agent right so this is the reducing agent and then this thing okay good hey so when I take a look at this half reactions are a way of showing the gain or loss of electrons we can balance half reactions using the following procedure balance all non oxygen and non hydrogen elements then balance oxygens using water balance of hydrogens using a high and then balance charges losing electrons some half reactions are super easy what do you have to do to balance this reaction to electrons you don't have to do either of the first three steps right where am I gonna put the two electrons on the left side or the right side is this an oxidation or a reduction half-reaction we always you always look always looking always look at your starting material is this thing combining with electrons do you see this + electrons no no so it's losing electrons so this is oxidation if that thing is not combining with electrons this + electrons then it has to be oxidation yes if you yeah okay the next one how do you want to start balancing this IC O's and I see some other stuff like so what what do you want to do first you don't want to add water you want to balance the non oxygen non-hydrogen elements first what do you see that's not oxygen and no hydrogen iodine how many you got on the left side how many got on the right side - so that's a problem right we need two of these now now that we're done balancing the iodine's now we can move on to water so how many waters do you want to put on whichever side you want to put six on the left or the right side right right so six so how many hydrogen ions doing but yeah I want to put 12 - where do you want to put them now is this is this balanced it doesn't follow our tool us it follows one of the laws would you agree it follows the law of conservation of mass but it does not follow the law of conservation of charge we gotta add electrons where do you want to add them left side or right side okay let's figure this out what's the total charge and what's the total charge the left side is positive 10 the right side is zero so where do you want to add electrons probably the left side right 10 electrons on the left-hand side okay so now now those 10 electrons cancel with these 10 positives and we got a charge of zero so we're fine right good label the half reactions is oxidation or reduction Kate that top one was oxidation what's the bottom one would you agree this is reduction this is gaining electrons yeah Jonah's hey let's build some half-reactions we can balance reactions would you agree this reaction is not balanced straight out of the gates you can you hopefully tell from a mile away yeah because what do you have on the left side that you don't have on the right oxygen this is not balanced so there's two ways there's two ways to balance whole reactions you knew the half reaction method or you can do the PA fu method now some people like half reactions some people like PA fu does it what did I not say after you and I said PA okay let's balance this yeah I'll email you when it goes up and you push hey let's separate this Shh into two half reactions what the hell's SN selenium no I always get caught on that one it's I'm glad you know what selenium is like most people don't even though some use an element that's fine so accent what's that said turning into so SN is turning into a genetic to plus how would we balance this half reaction to electrons boom love it done okay moving on to the next one what is permanganate turning into manganese 2 plus right so we need permanganate to turn into manganese 2 plus how are you gonna balance this are there any non oxygen hydrogens that need balanced there's manganese but there's one in one good what are we gonna balance next water I'm going to put four waters over here so now that I have four waters over there what are we gonna put over here hydrogen ions I mean this is on your data booklet but it's we can build it it's just as it's just as fast to build it so how can i balance this out okay the right hand side is +2 the left hand side is +7 yeah so there's a difference what's the difference between 7 positive 7 and positive 2 5 so I got to add 5 electron okay so let's make let's make a net reaction let's make a net reaction what's the lowest common multiple of electrons and moles of electrons need to be transferred so this needs to be multiplied by 2 this needs to be multiplied sorry 5 and 2 so let's just write this all out my guess is 16 hydrogen ions 5 SN 2 pluses [Music] then we're I can't believe you've done this I mean I don't know I don't know I like you understand I don't know what's on your diploma right you know like yeah but I know I know what's the relative probabilities of most of them right but yeah yeah that's right you're gonna have it you're gonna have a bromine reaction question you're gonna have a functional groups question right what's it you're going to have an oxidation state the chloride anomaly has been on the diploma for semesters in a row hey so that hey how hard was that like was that okay yeah okay so that's that smell hey there's always a check here we could always add up all our charges 16 positives and two negatives make positive 14 what's on the other side ten and two or four is positive 14 so yeah this is balanced that's totally fine now this was the first method Shh that's one method it's just as accurate as this method this method is the PAF huge even if even if you don't care for the PAF you method I still need you to just be quiet and not bother anybody else because maybe they need to remember what the PM what does PA nfu stand for okay I was really glad what oh there is no other definition for PA okay let's try this this did we have to do did we have to do oxidation numbers for the previous example no you have to do oxidation numbers here our whole goal is to identify what's being oxidized what's being reduced and balance them using the lowest common multiple of electrons and then we can balance non-oxygen hydrogens then balanced with water then balanced with hydrogen's in should just magically work out okay let's do the PAF you method the oxidation state for oxygen is negative 2 what does that mean the oxidation state for nitrogen has to be it would be +8 but how many nitrogen's are here in two of those so they each have to be +4 so the O is minus 2 and dichromate 14 but we don't want to cancel out all 14 12 12 divided by 2 is +6 good awesome if you want if you want to take that slowly then that's fine that's no big deal ah minus 2 so has to be +5 and then this has to be +3 so let's identify what's gaining and what's losing electrons the nitrogen and dinitrogen touch oxide lost it lost okay so this lost one electron per atom and how many nitrogen atoms are in here so this number times two right two electrons in the formula unit yes or no did the chromium's gain electrons yes they went from plus six plus three instead of becoming more negative so that's three electrons per atom and how many chromium's are in there so that's times 2 6 electrons so now I know we have PA and fu but you only care about fu that's the only thing you care about right so what's the lowest common multiple between 2 & 6 6 6 so the LCM is 6 moles of electrons I would bet that you're gonna have a question that asks you how many electrons are transferred in this reaction how many electrons are transferred in this reaction 6 moles of electrons right so okay so why do I have to what do I have to multiply any of these things by what do we know I gotta multiply the first thing by 3 and this the dichromate just leave it this is one of them right so 3 n2o4 and I'm gonna Ford those states because I'm lazy and we want to go quick + CR 2 O 7 2 - and oh look they give myself a little bit of room oh and now a three minus plus three plus cool now the rules the rules are the exact same as balancing half reactions except because this is a whole reaction we shouldn't have to add electrons the electrons from here and the electrons from there should cancel are we ever gonna have to up arrows no you can't have two things being reduced rate not with not without something not being okay so how am I gonna balance this what's the first thing you want to do yeah why am i stuffing a six in front of the no.3 okay what else am I gonna be gonna put a 2 in front of the chromium now are we done all the non oxygen on hydrogen's yes we are we're done the nitrogen's and the chromium's all I have left was ox is oxygens so now let's let's analyze how many oxygens on which side so there's there's 12 plus 7 is 19 and on the other side there's 18 oh that's easy so I'm gonna put plus 1 water on this side now let's look at the total number of hydrogen's cuz maybe there's hydrogen somewhere else how many on the left side none how many on the right side to now to that now that we put the water's ok so that's easy to H buses let's see if we boned up somewhere let's see we messed up is it perfect do all the charges are they all totally balanced yes they are the two positives and two negatives right two to one pluses is still two pluses and one two minuses so this side adds up to be zero and does this okay what what method what method seems like more work to you is basically split 50/50 stop some people love PA fu and some people hate pas building half reactions I find I find building half reactions more intuitive that's if you're if you're in a bind and you've got no clue what to do building half reactions is probably the easier method if you've got no idea what to do but the PA fu is faster so if you take five hours and 59 minutes I I will feel really bad for your brains yeah come up with a thumper sense then I guess it was worth it yeah okay but hey do you remember what spontaneous and non spontaneous means alright I don't pay attention I don't pay attention to how fast people come out of there I'm not over there at all okay so I'm I'm in here working on other stuff for the next semester that I cannot I cannot be in the room with you really I am I am I it is not allowed for your teacher to be in the same room as you when there's a diploma exam yeah I I could easily help you out on an exam right yeah yeah okay spontaneous reactions are down the hill on the table of half-reactions non spontaneous start uphill so is this reaction spontaneous you tell me I don't know well yeah maybe my dad hey does anybody want a data booklet okay thank you for being honest make sure is this spontaneous yes okay bromine br-2 liquid is way up here and lead is way it out here that's definitely down though right now Jonas and Jordi the reason why this is spontaneous is because when you put the two together when you go cathode - anode it makes a positive voltage right that's the reason why it's spontaneous it's got a positive voltage but we don't know that yet because we're only reviewing chapter chapter 13 so just keep that in mind so yes is the reaction spontaneous yes why because it's downhill that's like but the reason why it's it's spontaneous because cathode - anode is now what are we going to get when we were at bromine and leg what are we going to get what are our products and we're gonna get to VR now just this follow our two laws BR 2 BR 2 PV PV adds up to 0 adds up to do good ok awesome nickel 2 plus and copper is that spontaneous that's non spontaneous right when I look at it coppers way up here hey where's the nickel 2 plus way down there the reason why the reason why okay we'll just let's let's predict what what it would be first okay now I know that this is a non spontaneous reaction but we can still predict what we would get what would we get copper two-plus ions [Music] now it's the reaction spontaneous no why okay the reason why who is a stronger reducing agent who's the stronger reducing agent we had so we're not look at this copper who's the stronger reducing agent the copper or the nickels the nickel is the stronger reducing engine right so does it make sense would you spontaneously make a stronger reducing agent no stronger reducing agents mean they're more reactive right so are you gonna sponte if you had copper are you gonna make a stronger reducing agent than copper no the reason why is because nickel is a stronger reducing agent the copper the moment you make nickel it would immediately react with the copper two-plus to turn the copper back into copper so the reason why it is we say it's downhill we say that it's got a positive voltage like the proper reason why is because nickel 2 plus is a reducing this is where people where a lot of people got really confused about some things and it goes back to our idea of major entities do ionic compounds split up and when we put them in water yes absolutely they do do acids split up when we put them in water strong acids do right strong acids do those are the only two things that can split up so if you see an ionic compound split it up if you see a strong acid split it up as well and then you can take a look and you can see what do we get so list all the major entities identify all the possible oxidizing agents and reducing agents but most importantly identified the strongest oxidizing agent and the strongest reducing agent react the SOA and SRA together predicted the reaction is spontaneous or non-spontaneous right we react that's the way in that's our a using the lowest so a solution of nickel nitrate is that gonna split up or is it gonna stick together split up so what is it gonna make what two things do we get out of nickel nature we get nitrate I understand we get to nitrate ions to get that for everyone that's what's up we get two nitrate ions but it doesn't matter we get nitrate ions and then it's placed in a container made out of iron so what else do we have in here iron solid why is it not iron two-plus or ion three plus water if this was if this was metallic iron it's metallic iron is that this sound like an element to you and elements are always atoms they never have a charge right an element is atomic and it's doesn't how much charge okay what else do we have in here do we have water how do you know it's anything aqueous in here yes then we have one okay perfect so what in here try and find trying to use your data booklet and try and identify the strongest reducing agent and the strongest oxidizing well it's pretty hard when there's movement atoms with cylinders trust me your way this one's way faster okay what is nickel 2 plus that's our strongest oxidizing agent what is higher so we've got these two things and we don't just react them together you have to make your half reactions first right so nickel 2 plus is gonna make nickel and it's gonna accept 2 electrons and the process and the iron is gonna turn into an iron 2 plus and it's gonna give away 2 electrons in the process so what's the lowest common multiple of electrons 2 so we don't have to apply anything really we just add it all up you say iron solid reacts with nickel 2 plus 2 give us iron 2 plus and nickel soft and is this reaction spontaneous or non-spontaneous it is spontaneous good okay three hey-ya always glad I could help hey let's try the next one we've got hydrochloric acid we've got iron two-plus ions and we've got sodium nitrates and they're they're all being mixed together and we want to figure out okay what what is gonna be the reaction here what's the strongest reducing agent with some strong stocks aging blah blah blah blah blah so let's list all of our major entities what's the first major entity you see here I see hydrogen ions do you yes hydrogen ions and what else chloride ions what else I am two plus ions and what else I see sodium ions I seen nitrate ions anything else hold wacom woman how are you gonna be able to figure out what your strongest oxidizing agent is where do you start start up the top left just work your way down go one at a time go real slow too you have to have all the things in the half reaction or development what is your strongest oxidizing agent that's yeah that's awesome yeah that's really really good so the the nitrate and hydrogen ions that's your strongest oxidizing now what's your strongest reducing agent go from the bottom right and go up and go slowly figure out if you have all of those things do we have sodium in our mix yes not solid sodium we have sodium ions but we don't have solid sodium's to keep going what do you got keep going keep going do we have iron iron what I have two plus ions thank you going iron two-plus is one of those things that can act as both an oxidizing agent and a reducing agent and a stronger it's a strong reducing agent than water so the iron 2 plus is carboxyl very introducing so the iron 2 plus is our strongest reducing agent so we will we will write out those half reactions we will write up those half reactions and then we'll balance it over um can we skip this like all we're gonna do is write up the half reactions and balances can I is that like do you need me to show you how to do that no okay so but is this gonna be a spontaneous reaction yeah it is the the night Trade and the hydrogen ions is gonna be higher up than the FE 2 plus so I'm gonna move on because that's that's just doing something we've done a million times I feel like already yeah Fe 2 plus can act at in disproportion a ssin it could react with itself alright so let's let's take a look at this let's take a look at at this particular reaction and what let's see what happens in our in our oxidizing oxidation states so the oxygens - - so what's the nitrogen + - okay then we move on the next compound oxygens - - what's the nitrogen plus one so what happened to the nitrogen did it gain or lose an electron it gained an electron and then what about the no.2 yeah it's it's +4 so the nitrogen the nitrogen that we started with did they gain or did they lose electrons both they've both gained and lost some of them gained and some of them lost electrons it auto oxidized itself what that means is is what two of these molecules of no.2 of these molecules law are gained an electron and one of them lost two electrons okay you have to be able to identify a disproportion Asian reaction but it's pretty easy it's just it's a redox reaction that has how many reactants one it's got one reactive it's got many of itself that's all okay creating a table of half reactions some things to remember about tables of half reactions oxidizing agents right when you make a table of half reactions the oxidizing agents are always on the left side and the reducing agents are always on the right side so the strongest oxidizing agent is always top left and the strongest reducing agent is always pop or a bottom right so let's take a look at this and what are you thinking to yourself what are you thinking to yourself when you're looking at like these reactions yeah you're trying to figure out who won the battle for the electrons who ended up with the electrons and then whoever ended up with the electrons goes on top right whoever ended up whoever lost the electrons goes on the bottom so who who ends up with the electrons does platinum end up with the electrons or just rhodium who ends up being more negative in the end platinum so platinum is gonna go on top okay so PT PT and which which version of the Platinum should I put on the left and which version should I put on the right yeah whichever one is the oxidizing agent right so the platinum two-plus should go on the left and the platinum solid should go on the right and if you don't if you don't know just look at look at all of the metals on the right-hand side what did they all seem to have as a state of matter solid and what do they all seem to have on the left-hand side a charge with aqueous right okay so we know that rhodium rhodium is gonna go below platinum cuz rhodium lost that battle now to lyrium and samarium who ends up with the bathroom with the electrons to lyrium and samarium and like so delirium ends up with it so kind of kind of separately separately from this i'm gonna put two lyrium and samarium okay so kind of separately [Music] delirium on top turns into a delirium solid and samarium hey bourbon okay so now what we have to do is we have to figure out who's gonna go on top here like what in what order are these gonna be so to lyrium does tellurium win the battle for a row diems electron no no it doesn't so lyrium unsuccessful in getting rhodium is electrons so who should be higher to leiria morodian rhodium rhodium should be higher Wow so basically I'm just gonna put the two Miriam and samarium on the ball so let's double check let's let's take our table and let's just double check does it look like platinum two plus and rhodium should make a spontaneous reaction climb them to plus and Rohde yeah using our table that makes sense to lyrium plus and samarium should it also be spontaneous yes and tellurium plus and rhodium should to lyrium plus and rhodium be non spontaneous yes so this table works out perfectly fun what is our strongest reducing agent in this table SM solid right now SM 2 plus but SM solid what's our weakest oxidizing agent sm 2 plus right correct man you guys are packing up early why are you packing up early we're not done yet [Music] okay we're not gonna do the whole thing but we are gonna talk about this you you are mine for another three minutes and 20 seconds titrations titrations are not always acid-base and do not always have an equivalence point of seven right they don't have we can do redox titrations and if there can be tons of acid in there at the beginning and tons of acid in there at the end make sure your titration volumes agree within 0.2 mils of each other the highest and lowest has to be zero point two away from each other example of standardized solution of blah blah blah blah blah I just want you to figure out are we keeping all four of these trials okay but it doesn't matter if it's usually three are we keeping all four of these trials oh are you sure okay what no no why don't you figure out if we have to cross any of these trials on the last one why is it too high or too low too high so we're going to cross off this one and we're only gonna get our average volume from here on Monday the first thing we're gonna do is we're going to review the organic chemistry test then we're going to go back here finish the titration and then we're gonna start reviewing chapter 14 electrochemical cells