 Yeah, hi guys So, uh, you know, I can see that a few of you are there on the YouTube. There's Kirtana. There's Ananya There's Aditya You know, I can see that a few of you are there on The YouTube there. Yeah, but at the same point of time I see that show me is there on Skype guys, I would prefer if you can get on the Skype or hang out link, but if not, that's okay So all those who are there on the Skype it becomes easier for me to really interact with you guys You can also join the You know the Google hangout any of those because today it's more about a Conversation that I want to have with you guys then then then the You know theory part because we have done most of the theory even with electrochemistry I think we have spent enough time on those now show me. Are you able to hear me? Just a quick check? Aditya show me Excellent that's good Yeah, I have not shared my screen yet, so I will be sharing in some time. Aditya, are you able to see? Aditya, yeah, so Aditya is there on the call, but I'm not able to Find if he's able to see my screen or not show me. I'm sharing my screen now so that you should be able to see the screen From from here now. Okay Good, so you should be able to see the screen now. Yes, excellent. Perfect now So someone says that I they are not able to see Okay, that's Retry once now, okay I hope so there are a lot of people who is there on YouTube So it means that the YouTube is also working and hang out as well as Skype are also working That's good. Yes, I can see here now Okay, perfect, so let's begin guys, you know, so Coming to the point what what we had seen in the previous class. So we are talking about electrochemistry you know, there are some Discussions that I need to have on electrochemistry For you guys So what I'm going to do is I'm going to revise a lot of topics which I feel that we have already had a discussion on That's going to give you some boost in terms of understanding Electrochemistry topics all the guys who are there on YouTube. I want you to post any any Topics that you want me to revisit. Okay Someone is not able to join the YouTube channel So You join Skype or hang out Okay, so someone is not able to join YouTube Check the Capital and small letters Okay, so good. So these are the topics that we are going to really look at in electrochemistry today is this kind of a quick look at the previous topic so one is which we have discussed in a lot of detail is what is oxidation reduction and Reduction and redox reactions. Okay The second one is you can also what we'll also see is what are Redox reactions and equations. So this is the above is redox reactions. These are redox equations you can one second there is Still trouble for people to join in why is that still happening? I am seeing video unavailable. Okay, everything is correct It works Okay Okay, now the other part so redox equations is what we will see then we are also going to see what are Half reactions. Okay, what what are half reactions and half equations for that matter? This is what we have already seen. I'm going to spend very little time on that But if anyone has some misunderstanding get on all of these, please feel free to You know drop me a text or something so that I understand what really is You know, what topic should I really focus on? Okay, so that's that's one then What are direct redox reactions and indirect redox reactions? or indirect cells also Then we'll also see what are electrochemical cells and what are Electrolytic cells. These are two different electrochemical versus electrolytic This is one chapter which I want you guys to be really good at because it's it matters going forward a lot We are also going to see Daniel cell That's that's something that we have to you know, we are the quickly look at maybe we're going to spend Not more than 15 20 minutes all of these topics Daniel cell or then we are going to see what are other galvanics Yeah, the hangout also seems to be okay. Perfect. So I think everything is is is back on track One second, let me check if it's really working Okay, good so so these are the these are the points that so I was said talking about electrode potential So standard electrode potential what is oxidation potential and reduction potential? And which of these is do we really really see? Yeah, are you able to see now? It's not moving I'm going to share the screen once again from a car. Tell me if it works. It's moving now. Perfect. I think it's it's moving now Yeah, okay. Good Okay, so these are these are the oxidation potentials and reduction potentials that we will also see and their comparisons This is show me. Is it show me is it for you? I'll reshare I'll reshare the screen Yeah, I have reshared the screen show me. I think it should move now Even over feels a problem just feel free to bring back our talk to me. Yeah, yeah, so that's Yes, now coming back to the Yeah to the topic so this is these are all the topics that we've already seen Now quickly oxidation reduction We know that we have seen more than six seven definitions of oxidation reduction the basic Concept of oxidation is that your oxidation number should increase if your oxidation number is increasing That's your, you know oxidation happening there Now whenever someone is undergoing oxidation definitely has to reduce the other Reactant with it. So we also know what is reduction reduction is where oxidation number is going now below now when oxidation reduction happening Simultaneously, that's where it oxy reactions happen. It oxy reactions can actually be returned in two forms One is an ionic form and the second is what we call as the Molecular form now. What do you mean by ionic and molecular form is here? We talk in terms of compounds Okay, and You're sorry in any form we talk about ions and in molecular form. We talk about compounds Okay, we talk about compounds. So both of them are actually written depending on what what the Can't view the screen on YouTube or YouTube is still not able to see the screen Guys, let me share the screen. Okay, so I am saying in molecular there are compounds that we are written a common example is where you know, for example, in this is Zn plus Cu 2 plus plus SO 4 minus 2 minus giving Zn 2 plus plus copper plus SO 4 2 minus Okay, so this is this is an ionic Way of writing reactions and in molecular form. It could be for example FESO 4. Sorry Cu SO 4 you know plus I will take your zinc only because You know just to show a comparison you end up getting Zn SO 4 plus copper Okay, so this is a molecular way of writing reactions What is an half reaction half reaction is that where you are only showing oxidation and reduction? So if I have to show only oxidation I will show that Zn actually is ending up with Zn 2 plus plus 2 electrons So remember in oxidation Reaction you will have to balance the charges across the arrows on both the sides Whereas in reduction reaction you end up doing Zn Sorry copper 2 plus because copper is getting reduced here You know Copper 2 plus plus 2 electrons going to copper. Okay, so these are half reactions What is the significance of half reactions is half reactions actually tell us What is happening happening in a half cell? So it's not necessary that both the reactions should happen in the same container or same vessel for that matter You can have reactions happening in different vessels and yet at the same point of time creating chemical energy Into electrical energy and so forth So these are half reactions then what are direct and indirect whenever the reactions happen in the same container We call that as direct redox reaction whether when whenever they happen in different containers We call them as indirect The the beauty both of them have the plus and minuses So what is the usefulness of a direct redox reaction is we don't need a lot many Immovable parts like a solvage You know the dissolution and the reaction rates are very high So zinc and if we are using for the matter of zinc and copper zinc can dissolve faster reactions are faster Mechanisms are faster resistance is lesser. All of these factors are very important. The energies are conserved maximum Electrical energy can be taken out. These are all the factors of direct redox reaction The the problem with direct redox reaction, which is actually missing in your text also is that in directly redox reactions We we cannot it's very difficult to actually Separate out impurities. It is difficult to separate out substances at the end of the reaction If you want to reverse the reaction and charge Substances the efficiencies are very low in the reversible case. So for example, you know, you have your zinc dissolved and Copper deposited in a direct redox reaction So if people who are still not aware about what direct redox reaction is for example We take a container and we put both the electrodes in inside it So this is a zinc electrode. This is a copper electrode and we connect that to a Battery, okay, so when that is happening, we will find that either we connect to a battery This is the reversible case and if you are connecting it to a load, okay So let's say a resistance or a light bulb or any of these things then it becomes an electrochemical cell So in an electrochemical cell Let's say this is zinc and this is copper then, you know as zinc dissolves You'll find that the impurity will be formed here and as copper starts getting deposited This becomes fatter and fatter now if I have to reverse this up for some point of time Let's say I convert the electrochemical cell into an electrolytic cell That is the only way that I can reverse the reaction Okay, so then what happens is that all the copper that has to dissolve now in the reverse reaction Where zinc would be here and there will be deposition on the zinc whereas copper will be Dissolving and now you know so your zinc was dissolving just Make so now I am convert. This is an electrolytic cell because I am converting an external battery In this scenario if I have to drive it further if copper has to dissolve You know, this is going to be the negative and so this is how the battery would be okay because all the electrons would Be no, it's the other way round. Sorry. Yeah, so How do I decide this whether this is the positive and this is negative is because when copper is going to dissolve It's going to give all the electrons. So the electrons are going to end up being here So electrons have to come from your and and get inside the other other You know side of the battery now the idea is the drawback of a direct cell So these are direct cells why direct cells because both the electrodes are in the same vessel The problem with this is if I have to reverse Depositing copper back on to a zinc back on to it's electrodes So this is zinc and this is copper is difficult than In a indirect cell in an indirect cell I only have an environment or Electro-lightless electrode of the same stuff there for example. Yeah, let's let's compare this Okay, so if I would have had an indirect cell it I would only have had zinc Okay, and Z in S of four solution Whereas here I would have had copper and C us of four solution. So the interactions are much stronger and the reversibility is much larger Okay, so I will have to connect this with a zinc. This is an indirect redox reaction. Okay And now Okay, now, let's let's look at Yeah Now, let's look at what are the advantages of indirect redox reactions one advantage of indirect redox reactions is the studies of the reaction abilities for example You know if we have You know Zn dissolving which is an oxidation Vessel so this is an this is an oxidized in not in the electrochemical series But here this would be oxidation and this would be reduction that is happening here We are able to study the properties like its rate of reaction the amount of substance deposited all of that pretty well You know, we can determine All of the parameters distinctly. That's not possible in direct redox reaction. So that's an advantage of indirect the disadvantage of indirect redox reaction is there is a lot of You know resistance because now the ions have to travel through the salt bridge There are a lot of inefficiencies that will be built in because of this The energy will be spent unnecessarily the hunt efficient, you know, the output will be lesser So all of those are the drawbacks of an indirect redox reaction. Okay So that's about direct indirect now. Let's look at what's the next that Topic yeah, we now electrochemical series and electrolytic series electrolytic series is when so this is this Distinguished between electrochemical electrolytic is something that is very important It has been asked in your exams previously also twice in the law in the past two or three years a direct question from this So what is an electrochemical series as does any galvanic series for so if I have to really write this Let me write is electrochemical and electrolytic So some point of difference that I can I can directly mention to you is the first point of difference is Your electrical energy is produced. Okay, so electrical energy produced and here it is consumed Okay, your electrical energy is actually consumed The other thing is that, you know, this is this is what we call now commonly as a battery Okay, and this is what we commonly called as, you know Electroplating engine or You know, so this is this is more from a Uses perspective. So this is used as a battery. This is used as a Electroplating reaction now here the reaction is spontaneous. It is natural natural spontaneous You know, it is Yeah, spontaneous It is self-driven basically it is self-driven. Okay, which means that the chemicals themselves are willing to give out this energy Here it is an external energy or external work that I have to do External work or external energy is what I have to I have to supply to the Electrolytic cell and that's when the cell will work without that the cell is not going to work now generally in electrochemical series, you know, we have the cells set up in different Vessels so therefore this is mostly an indirect This is an indirect You know redox preferred and you're mostly direct redox is preferred Okay, direct redox. The reason is in direct redox the electroplating is the strongest because we need least resistance So we need less of the work to be done. So therefore here it is preferred here My direct is preferred is because we want to study The abilities we want the impurities to be minimized We want more control on the reaction and therefore your indirect redox is preferred here direct redox reactions are preferred And therefore the number of parts that are your is including with a salt bridge and here we don't have a salt bridge Okay, generally salt bridges are our day that does not mean that electrolytic cell cannot have a salt bridge It simply means that we are choosing not to have a salt bridge. Okay, so that's that's that's one more difference that we can have Of course the anodes and cathodes, that's one very important aspect So from an external perspective last time we told you that what are external and internal perspectives? So from an external perspective in a electrochemical cell anode is negative Please note anode is negative and cathode is positive Cathode is positive where whereas from an external perspective here when I see when I say external This is just for your understanding. It's not a scientific term But because people confuse in this time and again when we look from outside the cell is what I'm talking about we find that anode still has a positive charge here and Your cathode has a negative charge the definition of anode and cathode are given by Movement of cations and anions this this year to please remember movement of anions and cations inside Move and cations. These are the ones which define anode and cathode. Okay Anode cathode right now some of the most You know twisted concept that we have is I'm going to quickly again go through the salt bridge and you know last time We did this for the second time probably we are doing now for the third time But even in spite of that I will you know, I find there are there are a lot of doubts with it So I'm going to talk this about about this anode cathode Concept one more time. So let's say we have two electrodes and two separate cells I'm not drawing the salt bridge just to avoid a lot of parts So if we connect this to a salt bridge and we have a zinc here, which basically Dissolving into Zn2 plus 2 we realize that zinc is basically giving out electrons Okay, so zinc when it dissolves there are a lot of electrons accumulated and it gives out electrons So this is the one that supplies electrons So if electrons are supplied here and this is copper copper actually is getting deposited So copper ticks in the electron So this is how electrons move if I have to talk about current the current is exactly in the opposite direction because the movement of the electrons Is the opposite direction of the current now this entire cells if I have to replace by a battery You'll realize that the battery will look something like this So you would have a current sorry the the the resistance or the load whatever work we are doing and since the current is moving in this direction We will have the positive here and the negative here Okay, so this is how the battery will look like this is a positive negative and hence this ends up being an anode Sorry this become ends up being a positive terminal rather than an odd I would say a positive terminal and this ends up being the negative terminal But if you really look out here since anion is moving towards this this is an anode and Yet the anode turns out to be positive here here since cations will move you know and cations are moving away Sorry Yeah, so so cu2 plus is is a cation actually, okay, and Electrons moving you're taking correct That's right, so this is our eye. This is how the electrons move Yeah, and and therefore is yeah perfect plus minus right now Since this has to be cathode. I'm sorry. This has to be cathode Yeah, because cations are moving towards the electrode. So therefore this ends up being a cathode Now if you really see that the cathode is actually the positive terminal because this is how the cell would look like and this is a comparison of both of them So cathode here becomes positive Yeah, because see this is a cation moving towards an electron and hence it's a cathode and The current is moving from the cathode towards the other electrode. So it has to be a positive terminal Whereas here since cation is moving away So therefore obviously the negative ones will be moving closer or the electrons will be moving closer This ends up being an anode But if you really compare this anode to the battery here anode is where we have negative terminal Okay, so this is this is a tricky part which you know, you should really remember how to distinguish between cathodes and anode and What is the difference between their charges in an electrochemical cell and an electrolytic cell now apart from this Quickly checking if everything is good on the redox reactions again. Okay Okay, that's right Then let's let me check at Skype if there is any questions there Okay, no hand on hangout everything. Okay Perfect. So now let's go to the next topic which is How do what you know the electrode potentials and how to really a certain the electrode potentials now We have realized in the previous class that you know, electrode potentials can be defined in multiple ways. Okay To define a little potential. It is a very relative quantity. Remember all potentials are relative There is nothing called as an absolute potential We talk potential with respect to something for example when we climb the mountain We talk that we have a potential with respect to the surface of the earth when we are talking about large objects in space An object in space has a potential with respect to some other objects For example with earth if we talk about it, then it's an object is there in space We'll say what is the potential with respect to earth, right? Similarly in this when we talk about potentials we talk it about what what is it with respect to hydrogen electrode? Okay, hydrogen electrode hydrogen electrodes potential is considered as zero, you know, and This is also called as this standard hydrogen electrode in you know, like a So it's like a reference point, you know The one that we actually benchmark everything with now when is the standard hydrogen electrodes potential assumed to be zero There are certain parameters to that when the H plus concentration So what is the standard hydrogen electrode last time also we saw that we make a vessel in this vessel We actually put a glass tube Okay, a glass tube and there is a platinum wire with a platinum black box. Okay a platinum black plate Why platinum because it basically helps in Maintaining the pH at a more stronger level. Also, it actually works like a Add Sorbent to actually keep hydrogen, you know gas hooked on to the plate So platinum is like an adsorbent which will keep gas in the liquid also. So that's that's one So what are the necessary conditions that we have to do here is that of course? We have to maintain the temperature as 298 Kelvin, which is your room temperature We have to maintain the atmospheric pressure as one atmospheres We also have to you know, see that the molar concentration of H2 and H plus is one molar, okay So the hydrogen concentration is is one molar. Okay, so this is this is very important And once this is set up then whatever is this electrode connected to and whatever reading we actually get on a volt meter So, you know how we take voltages, right? We take it on a volt meter So when a when a volt meter is connected to let's say any other substance That voltage considered as whether it is positive or negative either of that is considered as the standard electron Road of that reaction. Okay, so electrode potential is always about a reaction So let's say I connect this to zinc to Zn plus two so zinc and zinc sulfate solution It will be the standard electrode potential of zinc can zinc sulfate now standard electron potentials can be both Oxidation and reduction. Okay, either ways now when we write the electrochemical series So, let's say what how does this voltages look like? So for example for sodium It might look like 1.6 1.96 to you know, so I'm actually going to show you some numbers of standard electrode potential So that we have an idea about A standard electrode Potentials so here's a Yeah, here are a few Maybe I'll look into Yes, if you really see the here are all the standard electrode potentials. I hope it is large enough Maybe I can zoom this a bit for you. Yeah So you see all the electrode potentials are given now if you connect hydrogen to all of them You'll realize that for lithium sodium and all of those the electrode potentials are given in negative here But they are negative because these are reduction potentials Which means that lithium cannot reduce if you connected to hydrolyte hydrogen lithium will prefer to get Oxidized and it will try to reduce hydrogen and therefore if I'm talking about the reduction potential the reduction potential is negative because it's behavior is is exactly opposite of What we are measuring here as whereas if you connect hydrogen to any of those like copper You know, you connect it to oxygen iodine even up to fluorine these guys will easily get reduced and Depending on their ability to get reduced their electrode potentials are much higher For example in this scenario the electrode potential is almost 2.87, which means that it is excellent reduction reagent with respect to Sorry, it's excellent oxidizing reagent of hydrogen and itself getting reduced with respect to hydrogen, okay, so Now both of these, you know can be written the this standard reduction potential can also be Measured so the point here is if I connect a hydrogen electrode to any of these I'm going to get a voltage. Okay, and how the voltage will be I will have to decide the direction of that Also, for example, if the current is flowing, let me draw this for you So let's say the current is actually flowing in this direction. Okay, then I'm going to so voltage is going to the Indicator here is going to deflect in either directions on left or right I have to decide which direction will I consider it as positive and negative if the current is flowing into hydrogen Then this is going to be positive. Sorry. This is going to be negative This is going to be negative because the current is it gets into the negative terminal and this is going to be positive Right now in this scenario since the current is flowing Therefore hydrogen is getting oxidized. Please remember wherever the current flows It gets oxidized and opposite direction of the electrons is also oxidized So if this is the current direction the I direction the electron flow direction would be in the opposite direction This is E minus direction. Maybe I can draw it with a still different color. So this is the electron So wherever current flows, this is getting oxidized So if this is getting oxidized obviously, this is the one that is getting reduced And if this is getting reduced then whatever potential I get here if I take that as positive It will be the reduction potential It will be the reduction potential if I actually take that as negative. It will be the oxidation potential So I decide it is our choice to decide that which of them I'm going to consider as positive or negative and depending on that I will name the potential as either oxidation reduction potential. This is a very tricky point And I'm going to say this again one more time is sometimes you are just given standard electrode potentials If nothing is mentioned, if nothing is mentioned, you have to consider that as standard reduction potentials But if they have clearly mentioned that this is the standard oxidation potential If they have mentioned standard reduction potential there is no doubt about it Standard oxidation potential also no doubt about it But if they do not mention what potential it is then it is always standard reduction potential This is kind of a subconscious or unwritten rule that we have in chemistry Where we talk about reduction potential This is again something that is very difficult to figure out if you are not aware about it Now so that's finding electrode potentials Once you know different electrode potentials as in this You are able to find how much the potential will be generated In fact to tell you that the hydrogen's electrode potential actually even if we compare with other You know CVs for example, let's say I plug the hydrogen electrode into our socket tomorrow It actually gives us the amount of current that will flow If we devise that I will be able to find out that hydrogen's potential actually turns out to be zero So how do we say that in our socket, let's say our 2 pin plug You know third pin is anyways neutral So let's say this is the 2 pin that you actually put inside a socket When we say that this is actually 240 volts What does that really mean? It simply means that the difference between these two is 240 That does not mean that one is at zero and the second is at 240 only No that's not that's not true Sometimes it might so happen that this is at minus two and this is actually at 238 Then still then the difference is 240 So what is the difference is what is needed We don't need that this has to be zero and the one has to the upper or what we call as the life Is always at 240 that's not necessary Similarly when we actually connect the hydrogen electrode We actually find that what are the potentials of each of these So because all of so if we connect with the hydrogen I will get this as minus two and I will get this as 238 Because hydrogen electrode is something that we consider as zero And that's the benchmark of considering all electrode potentials even in electricity Okay, so it's not that the electricity is in chemical and in Electricity is in electronics or electrical engineering are different It's just that their correlation has to be understood Okay, so that's that's with electrode potential We've also seen in the last class how do we find the voltages of different cells I want to quickly pause here for a minute to really see if all of you are there following Or am I just having a monologue here Quickly if you can just respond wherever you are Whether you are on Skype or whether you are on YouTube With a quick yes and no So that's That's show me because it's yeah, perfect. Thanks show me Who else is there on the Skype here? There's one more Aditya, I guess. Yeah, all all the guys who are there. Okay. Yeah, that's perfect All the other guys who are there on YouTube can you quickly? Yeah, I can just see a little there How about Kirthina and Ananya was there Are you guys dropped out? Are you able to connect? Yeah, so Kirthina is there. That's good. Mansi is there. Arpita is there. That's good Nice Okay, perfect. I think Ananya must have dropped out probably Okay, that's good. So a few of you are there. Most of you are not here today But I'll put this on the YouTube as well Is there any questions that you have? Okay This is most of the theory part that we we have looked at But is there any questions that you have? Just go ahead and type it on the screen or wherever you are If you have any that is Okay Okay, good. So now we will just quickly look at a couple of other theory points You know, because I think the discussion is still not Happening here, but okay. So now what's a what's a dry cell? Okay Now it's been ages that we have been using this pencil cells or you know And there are multiple types of these pencil cells a cells two a cells two a plus cells I'm going to tell you something interesting about that as well You know most of the times you go to a shop and you actually You know try to buy cells, right? What are those a and a? I'll show you that for a minute. Yeah See all of these images that you actually see So this is this is what your a battery looks like, okay? And I don't know if they have given nomenclature. They have not there are multiple types of even fatness thickness that these cells come with Okay, and yeah, so this is yeah, this is where it is So look an a uh Yeah, show me. Did I lose you? Yeah Okay It's hung Okay, uh, I am resharing Is this I hope the screen is not hung on the youtube Okay, you can see it. Maybe I'll just check with the youtube Guys Yeah, I think it's there on the youtube also now Yeah, probably I lost you for a bit, but now it's back Okay Yeah, so what I was saying guys is that all the pencils that you actually go and buy in the market They have different Names, okay, so they like I don't know till where did you hear it? But I'm just going to say so the smallest one is a triple a and the larger ones are double a So please note that as the size decreases the number of a is actually increases the other way round It's not it's not the way that uh, you know, we so this is an ever ready cell box type and So if you can see this is a double a cell, this is a triple a cell, okay? And this could be a c and this could be a d type cell Yeah, this is the one now if you see all of these cells, let me see. Yeah, all of these cells are 1.5 volt I don't know if you're able to read here They're all 1.5 volt now if I have to increase the voltage I generally would put just a cell behind the other so two cells on top of each other will give me 1.3 There's one very important thing that I have to tell you see what happens if I put this battery over this battery will I get that You know adequate voltage of three volts. Yes, I will but that is a very bad thing to do And I'll tell you why is because this battery has a lot of charge to really get into but Yeah, so this battery actually has Huge amount of charge inside it but The smaller one has lesser amount of charge now if you force a lot of charge to move So the current that you are Making happen that current will actually consume the smaller battery faster And since it consumes a smaller battery faster The bad battery will actually hamper the performance of the higher battery Now, please note in batteries if you have one small it's like rotten mangoes, you know one mango is rotten All the other mangoes will rot very fast. So if you have one battery that is Not functioning very well It will try and ruin the other batteries because the other battery will try and force the charge But you will not be able to give the performance Because the smaller battery is restricting that performance and hence it is a very bad idea to do that But having said this you will still be able to achieve the potential that is needed So in most of the scenarios, you know, they actually say that If you are stranded somewhere and if you really need a particular voltage to let's say charge your Your your cell phone. So a classic question that it's always asked is We always connect our cell phone to our laptops and our cell phone can get charged But can you actually charge a laptop from your cell phone? And the answer to this question is yes It is not the size of the batteries that matter that who is charging whom It is the potential or the voltage that you are using that matters So if if a battery of a cell phone has a higher voltage It will charge the battery of a laptop also The only difference would be that the That the charging would be very small for the for the laptop because the entire energy that the Battery has with little as compared to what a laptop battery would have So that these are some tricky things about batteries whose concept should be very clear Now coming back to a dry cell, uh, it's you know, this is something that is that is involved in your syllabus, so A dry cell is you know, the first uses where they're actually 1868 and generally it's all all these dry cells are of 1.5 volts How it really works is you actually have a carbon rod and it is surrounded by so let me draw a figure for you I'm not sure if the figure is also there in your textbook, but if you don't have you can actually use this In fact, we have the figure here. I can just use the help of that as well So me really drawing it save it will save some time Yeah, so you basically have a carbon electrode and the carbon electrode is the metals. They're not really Mentioned here. It's actually covered by a mixture of mno2 and powdered carbon And what what is done is zinc is filled in the container with nh4cl, you know all around it Let me see if I have The one with mno4 written on it Maybe this is the one still not there Here it is. Perfect. Yeah, so you see there is a carbon rod and this is just a jacket, you know, which is generally of stainless steel something that is not very Corrosive which can resist and which is durable enough Now you see the anode material is of mno2. So this carbon rod is does not touch the lower tin plate Okay, the tin is the one that they use to conduct and zinc is Stainless steel is what they generally use to Resist or a pvc jacket also inside that is to as an insulator now What what really happens there is also an nh4cl that is put inside this which is not actually Mentioned here. So what are the reactions that happen here is basically zinc and carbon are the ones that so carbon is used as an electrode but zinc can Mno2 nh4 are the ones that actually trade the electrons So when we say trade the electrons is basically they are the ones that exchange the electrons So these are the two reactions if I have to write zm gives zn plus two Plus two electrons from the Zinc chloride solution that we have and it is the mno2 and nh4cl that that actually takes the Electrons so nh4 plus plus is takes those two electrons To have a fused mixture of mno mn2 o3 Plus twice of ammonia Okay Now as more and more ammonia actually comes out the cell starts dying So I'll tell you one more good thing if you if if some time at some point of time you actually have to Charge a dry cell battery. You can just take ammonia water, which is readily available in stores You know since this ammonia is released The it is difficult to charge a dry cell But if you are able to put ammonia water inside the dry cell just you can just take a syringe or something and put Ammonia water and then actually Put small amount of current in it not very large because if you put a very large amount of current You'll find that the cells tend to explore because the reaction is forced very strongly onto them But if you are able to put small amount of current into it a current with a voltage of about one volt or Or so you will find that you will actually be able to charge the dry cell Because this ammonia from the ammonia water ends up going giving out mno2 and nh4 plus Whereas zinc actually ends up zinc solution ends up being zinc metal and So if you actually break a dry cell, you'll find that a liquid flows out You know out of it all that liquid that flows out is nothing but A solution of water and mno2o3 Okay, and it also a lot of ammonia is also given out So if you really smell that smell a dry battery, you'll find that it's it typically smells like zinc Which is a what we call as the iron smell or iron taste, you know metallic metallic smell or metallic taste And you also have ammonia coming out of it. So this is one The the cell is see, you know if I have to speak something more on the cell It's basically the Diagram that is very important. Now. How do we have seals? These seals are basically used for insulation. The metal cap basically is used to Transport the charges carbon electrodes are used because carbon electrodes are the most durable and there is a lot of carbon Dust also that is used inside all of these carbon dust help Make electrons move through mno2 mn2o3 and ammonia and zinc all of these three are Involved, I don't know if there are some more reactions dry cell Dry cell reactions I can show if Yeah, this is this is the one so this is the core reaction There is zinc plus mno2 plus water actually gives mn2o3 plus z in hydroxide. Okay Uh Let me see if some yeah, there's this is with the nh4 cl the same with nh4 cl So see z in hydroxide is not very stable. So therefore there's ammonia also help it convert to zinc chloride Which is also a very stable compound So mn2o3 and ammonia is released plus electrical energy is given out These cells go for a very long duration, you know So so long that you are not able to not not using the electrical energy the reactions can be prohibited Uh, you know Now one more important point that I need to tell you about dry cells and another interesting fact is that After you have removed the cell it takes some time for the cell to actually You know stop sending electrical current. So let's say you connected this electrical current to a Bulb and the bulb is now lighting with the dry cell Now as soon as you remove the bulb that does not mean that the Energy or the electricity given by the dry cell is finishes, you know It takes some time for this z in an mno2 to still give some electrons And once those electrons are given out the electrons accumulate so much on the karma electrode that no more electron can be taken out And that is when the reaction stops Uh, and hence whenever you take a battery and put it uh into a new uh, let's say an old uncharged battery or a dying battery If you take the dying battery Leave it for a day or two and then whenever you put it into Another torch in the very first instant you will still find that the light will come up and again It will die down and why does the light come up is because over the two days There are some more electrons that get accumulated here and as more and more if you remember chemical equilibrium More and more electrons are accumulated. Uh, you know, they get into an equilibrium where no more electrons can be saturated There so if you remove the battery from a working model, uh, it takes For you know for a typical dry cell it will take a few seconds or maybe less than that But for normal very resistant batteries. It sometimes takes days to actually accumulate a lot of uh, electron and There you can also use a dry battery After a day or two after it's completely died out. So this dry cell is something that's also very important that I suggest all of you guys really look at Yes, so now talking about another You know battery I would say Which is your lead battery, you know lead storage batteries or the ones that we use in car engines So dry cells are generally used for household purposes or for travel leisure entertainment, you know, so for all your cameras and In fact, even the cell phone battery that you have these times these days you have My own battery something that I would also like to show you on lithium ion batteries is its reactions Uh And it's construction. Yeah, so this is this is your typical Mobile phone batteries, you know, so you actually use lithium's and On the other side you actually use any metal oxide But most of the times you actually use metal oxides that are from calcium cobalt I also have seen copper oxides being used. I don't know if let me see if I'm able to find a copper oxide reaction for you So this is your your typical lithium ion, right? So how does it work is? They are not really seen here. Let me show you Yeah, so these are all, you know, the small ones are all your, uh Uh electrons, yeah, and the red ones should be your Protons or the positive charges. So if you see that the electrons all the negative ones Uh, yes, that's right. So all the negative Uh, uh ones are, you know, are actually taken out. So this is a mixture of lithium and silicon This is a mixture of lithium and some metal oxide Uh, so lithium's are the ones that actually give out The electrons and the metal oxides are the ones that actually taken So here's a lithium cobalt reaction. So at cathode, uh, lithium actually changes giving out electrons and at anode Now you'll find that the same lithium ions with carbon are actually being converted into a carbon lithium complex This can also be a silicon lithium complex. Sometimes they use germanium lithium complexes The key part is that the lithium itself is actually giving out electrons and forming compound Okay, so as more and more of lithium compound is formed We find more and more of the energies given out By lithium ions are better. You must have heard that lithium ion are much better than Your dry cell or even your lead acetate batteries or sorry lead sulphate batteries And that is because the efficiency of lithium giving out electrons is much better Also the equilibrium between c li x and the lithium ions is achieved much faster Why is that important? Uh, is because uh, when you have uh, c li x actually in the solution If we have leakages of c li x getting out or very unstable Amount of c li x without really taking out the electrical energy We will find that the lithium positive lithium will keep on getting into lithium positive and making carbon compounds So we don't want that right? Uh, so once c Li c is achieved We and if you're not taking out any electron from the battery, we want the reaction. This is these are all reversible reactions So we want the reaction to stop If if the reaction does not stop which happens a lot of cases in dry cells or even in your lead Lead acid batteries is even after the we are not taking any electrons Some amount of this substance will get formed because of what we call as leakages, you know Leakages to multiple stuff, you know Covering or even to you know, because there is enough not enough energy To oppose the reaction. So electrons can be lost there So those are lithium lithium ion batteries Let's also talk about lead storage batteries Now lead storage batteries are again lead working with lead itself So, uh, maybe I can show you that those reactions also So like lithium goes to lithium plus two and forms compound their lead is going to uh, lead Uh, lead sulfate Uh forming compound. So these are all different types of lead sulfate. So this is a typical lead acid battery. So you have uh, Lead oxide on one side and lead on the other side. In fact, these plates are alternately placed Maybe yeah in this it can be seen that these plates are alternately placed that maximum contact can be achieved between Lead oxide and lead by maximum contact so that more amount of ions can be exchanged The reaction is very simple PBO2 has PBE plus two and You know all the lead actually dissociates uh forming PBE SO4 and gives out all the Electrons so as PBE goes to PBE plus two electrons are getting here which are used as a current And these electrons then come to the other side where more of PBO2 is is uh Is produced now you you remember lead acid batteries We have seen that we keep on putting water, you know at home also You will find that distilled water is added a lot many times the reason there is look all the electrons that come from this cathode and then it reaches PBE Here you will find that Uh, the electrons have to be absorbed by someone. Okay, it's either this hydrogen that absorbs the electrons Or if you have any PBE plus two in the solution that will absorb the electrons to get deposited at this point, right? Now when hydrogens are getting absorbed, uh, uh, you know, either it, you know, we have to end up getting hydrogen gas or You know, if you do not have enough water in it then the pH of the water Will not be maintained. That's point one point number two is that You know, we also need a cooling effect With all the batteries being used. There is a lot of cooling effect that is necessary Maybe this is the one that where here you will apply much better So this is PBO2 which reacts with sulfuric acid to form lead sulphate So, you know PBE from here Is actually giving out all the Giving out PBSO4 And so the PBR is already in plus two actually it gets into PBSO4 here is the Lead where it is getting into plus two form and giving out electrons All these reactions are there in your text as well. There is Not much to really know on it, but yeah, this is this is a typical lead acid battery where lead and lead Dioxides are Arranged one. Here the voltage is actually two point one, you know, roughly about two So you generally use six. So it's these are all 12 volt batteries, you know So earlier if you remember dry cells have generally 1.5 volts lead acid acid batteries are generally about 12 volt batteries Okay now Okay, so Maybe I can also give you handouts on this in the next class whenever we meet Yeah, so this is just a much of theories what I want you guys to do is actually go through your text You know on all of these battery issues or topics and if you have any questions, then you know, we can discuss that But that's the basic theories are these are three enter four four things that you will have to study in all the batteries Okay, so all the batteries or cells that we have the most important parts that you have to know is first It's the construction of this battery In construction. What are the parts? Okay, and what are their uses? Okay as in how does what what what is their role basically uses our role in the Entire segment and there is their position Okay position role so for example As we use pin in the outside of the dry cell Now lead is placed alternately inside the lead acid battery Lead oxide is also placed alternately and very close to the lead Chamber all of that is where the positions and all of this the second is What is the working of that battery? Okay, so in this working? What all do you get is you basically get half cell half cell reactions You also need to know so in half cell both oxidation and reduction is present You need to know the potentials that it gives You also need to know that What happens when uh, you know the what we call them as Uh, uh, you know supplementary or Uh, subordinate reactions. So for example in lead acid battery It is the lead who does all the work But it is h2so4 which helps maintain the balance of so4 minus so4 2 minus and h plus right So all of those subordinate chemicals that are there. What are what are its roles and how does it help the working? That's the second part the third part is uh, uh as a battery where it's uses It depends on the potential and it depends on other factors like You know the transportability of it the storage facility transport transportation and the storage Uh facility that it can have for example dry sales can be stored for a very long time But that's not the case with lead acid batteries. Lead acid batteries if you keep uh for six months You'll find that the lead acid batteries would generally Be useless because that either the air will you know, sorry the water will actually dry out And its efficiency will also start coming down. So it's very ideal to make a lead acid battery and start using the same So this is the third third is the uses parts and fourth, which is the most important is the figure Uh, so this has this this actually carries a lot of weightage Without the figure i've seen that people losing about a mark or two Generally the questions are some these batteries are always four markers So, uh, you know one of one of the most important questions that you should actually look at So these are all the battery questions that we have The last topic that I have on this chapter is about corrosion of metals You know different metals this corrosion also decide is decided upon the reduction in oxidation potential That is because uh, you know, uh, who is corroding is basically oxygen Okay, and when oxygen corrodes a lone metal, uh, there is some energy that is needed for it also to Form so this this is an o double bond so when it forms a o atom It needs electrons to be taken in two minus each to form an o two minus. Okay. Now. This actually needs electrode potential Or what we call as energy o two minus So this this is this actually has your electrode potential Standard electrode potential because it's the reduction potential now this reduction potential has to match with the metal Through which it is actually reacting. Uh, so, uh, uh, if if the reduction potential of oxygen is lesser This is an important concept that you have to know is lesser this reduction potential is lesser than the reduction potential of the metal, uh, uh, then you know the reaction than the oxidation potential of metal. I'm sorry This reduction potential will have to consider with the oxidation potential then, uh, we might not be able to get the Uh, you know, uh, corrosion happening. I'll give you an example Let's say in the reduction potential the energy given out by oxygen is 20 joules But let's say there is a metal m which goes to m two plus To form the molecule mo at the end of the day if this energy required is 40 joules Then this metal cannot be reduced by in the same situation if the metal goes to m plus at let's say only 10 joules of energy This will be a spontaneous reaction and we will definitely have corrosion happening. So, uh This we spoke in terms of joules. Uh, the same can be spoken in terms of electrode potential So saying that let's say o going to o two minus the potential, uh, given out is 2.1 volts But the metal going to m plus the potential required is 1.7 volts. This will happen Uh, whether or whereas the metal going to metal two plus the potential required i'm saying required It's not, uh, the spontaneous potential that is happening. Okay. So the potential required here is 2.3 volts To make me happen then, uh, it will not happen. Okay. Now, this is the required potential to oxidize So this is what I would supply. Okay. This is the supply that I will do in the electrolytic cell, for example If I write simply this, you know, when I when I write m going to m plus and I write here as 2.3 volts This is called a standard electro potential and which means that m going to m plus it gives me the potential If I'm not writing as a supplied potential or an electrolytic potential in common terms This would mean that m going to m plus is simply providing the potential to me. So this is actually a electro electrochemical potential or this I can call as the standard oxidation potential. Okay Minus 2.3 would be standard reduction potential. So what is the concept of corrosion? The concept of corrosion is oxygen itself needs You know, it gives out certain amount of energy when it goes to o two minus from o two Which is a molecule to an atomic ion An ion problem only, you know two minus that energy has to come from the oxidizing agent And uh, that oxidizing agent can be iron can be aluminum can be copper any of those You know, we all have studied this also that aluminum actually creates a layer of cover and hence it cannot be corroded further One of the major things of that also is that that layer becomes so strong That the oxygen is not able to have enough energy to penetrate the layer Break down the layer and actually form oxides of uh, aluminum further So the energy that That is given out by oxygen to form o two minus is not enough to actually break down al two o threes layers and From oxides of aluminum inside the uh, you know inside the aluminum vessel or You know container or whatever we are using so all of these corrosion Properties are also something that's very important. Now. What are the factors that can affect corrosion? You know, so first of all what what is very important is The necessary condition to have corrosion is we need to have oxygen in air But you know, there's one more very important condition is that we also need to have a presence of moisture or water And the reason for the presence of moisture and water is that is the one that Enables or facilitates the oxygen Iron movement as well as the cation movement. This is something that is always overlooked that and and you know, uh This is a question that we should have all the time is that see when we say corrosion is happening We are only talking about oxidation. So for example, f e goes to f e two o three But we have never seen this happening with plain Iron we've always found that f e goes to f e two o three Uh, only in presence of water Uh, you know, this is a question that we should ask ourselves why what is the role of water here because Is the water that is the one that is giving oxygen? Well, no What happens with water is it facilitates the movement of f e plus two and o two minus to end up giving f e two o three So oxygen definitely comes from the air itself Maybe a some amount of oxygen that might come from water But it does not have enough amount of oxygen dissolved that it can actually corrode an entire iron plate So definitely we need oxygen coming out from the atmosphere at the same point of time We also need water molecules to be there to actually help these uh hydroxide ions move in the water Or h plus ions move to take uh o two minus and f e three minus Moving in either of the directions to make oxidation reduction happen So these are the two necessary conditions for corrosion one is presence of oxygen and second is presence of water or moisture Now let's look at what are the factors that actually Matter, uh, or which which which help corrosion the first factor that helps corrosion is Or which increases the rate of corrosion. I would say, uh, let's talk only about what the rate Increase, okay So one factor that helps increase the rate of corrosion is of course, uh, having a presence of one more metal You know, which can actually work like a catalyst, right? So when the corrosion is happening now and if there are two metals If one having a larger Affinity towards corrosion, uh, it will actually increase The ability to corrode the other metal also The reason for this is because it just helps speeds of the movement and the activity of the oxygen ions Which can you know further be utilized to corrode both the metals? Yeah, so, uh, that's that's one. So I can say here is that the presence of another metal Yeah presence of another Metal which has more affinity to corrosion. Okay, uh, the second factor that actually increases the rate is You know, whenever the air is polluted with uh substances like NO2 SO2 You know the air has a much larger acidity in it And when we say acidity basically more of H plus ions Again, if you have moisture and you have such acidic conditions, uh, you know acidity themselves are very corrosive The presence of O2 minus ions are also very high. So presence of all the pollutants actually increase corrosion So this is they are these are also one of the factors which actually has a very higher rate of Corrosion in it. Uh, now, uh, how do we avoid avoid corrosion? Okay, so what are the Factors that we can do to or I would say Factors, what are the ways, you know solutions to avoid uh, corrosion? Okay, solutions to avoid corrosion. Uh, I would say that You know, uh, there are more six seven of ways to do that One is of course, you know, and you know some of them are very very easy One is basically to have it painted. Okay, uh, second is actually to do electroplating electroplating of You know elements that can actually, uh, they do not have more of affinity to corrosion For example, electroplating by aluminium, uh, even by the third thing is actually galvanizing something, right? So galvanizing is nothing, but we actually do, uh, electroplating of zinc, you know So that's the third the fourth is actually to do what we call as tin plating What do you mean by tin plating is you basically hit tin sheets on the rods or electrodes or metal Uh, and and you keep very little gap or mostly it is airtight very very similar to your dry cell So most of them if you keep it airtight then you'll find that tin plating can also reduce Corrosion by a large extent Yes, so these are these are some of the ways to actually do protection of corrosion from multiple solutions Yeah, now one particular corrosion of iron is what we call as rusting. We also know that And this this rusting is basically Uh, the one that is of the most nuisance because it's the the scale of rusting that happens Especially if you go to the gujarat and kachiria, you'll find that even cycles which are lying for a year or two On the road, you will find that it actually Wasting off, you know, you can just pick up the parts of the cycle and bend it with the hand. So that's that's a dangerous Consequence of the salty water that you have there again salt is another factor that can actually increase the rate of corrosion now the Corrosion of iron is something that we need to look in iron and aluminum are the two reactions that are important for us in the sense as to For example, the brownie flakes are given in iron In aluminum the it is generally blackish in color blackish greenish in color So So the color is important the reactions are important. You guys know the reaction So, okay one major thing that most of you ask is when iron corrodes does it form feo or fe2o3? Actually both of them in the end if enough time is given the final product is fe2o3 But till fe2o3 is formed a lot of feo is also formed and fe2o3 also is formed So it is actually a good idea to generally write this as fe3o4 and if if someone tends to Give enough time or if there is a clarity in in the question that is there This is the final product that would form so iron in this plus three oxidation state is most stable And therefore fe2o3 is what it would always like to be into right? So that's that's the That's that's the rusting of iron and of course aluminum has only one product which is al2o3 So this reaction is also something that you guys might want to Look into so actually this is the last topic that I wanted to really share today And this actually brings us to a closure of this Chapter there is no more Topics in this what I would do in the next class is actually have Faraday's laws and a couple of questions on What are really? We definitely going to have some more discussions Because here I don't know whether all of these topics you have been You know reaching to you or again as I said is just a monologue But we'll do problems on what on on the electrode potentials The problems on Faraday's are very important Faraday's law. We have seen that the Faraday's law is The amount of substance that is deposited the mass is directly proportional to the Charge that you make it flow through the electrolytic cell So if you remember in the last class, we saw that the mass is proportional to q or m is equal to z it Which is basically z is the Faraday's constant i is the current and t is the time so Now we have also seen an example where we can simply count the number of electrons that were given out During a certain amount of time and with those number of electrons. We can actually have mass getting deposited so Faraday's laws is something that I will also Look into in the next class and Okay, and then we'll also talk about some reactions. So how does the reactions Make us predict Whether uh, there will be an oxidation reduction or nothing will happen So finding electro potential is one type of problem But finding the reactions and their consequence on the cell is a second type of problem These are three types of problems and we are also going to discuss on the batteries and all of that So I would like to have one more session on electrochemistry because after this chapter There is only one topic that will be left with us, which is our uh, I think Uh, one second. Let me look at it. Uh, we have done metal sulfur also. We have done Uh, reads we have done Okay So the only topic that will be remaining is chemistry in daily in the service of man Is that what is hydrogen also remaining? Yeah hydrogen and uh chemistry in the service of man Maybe these two topics. Yeah, uh, yeah, so those are the two topics that might be remaining Again, I'm going to pause here for a minute and uh, since we are also coming to the end of the time We have 10 more minutes left. Uh, I would just like to look at uh, uh, everyone, you know, how Could you connect? Could you do you have any any more questions? Uh, who are there on the sky? Yeah Okay, so show me is good Uh, how about others who are there on the youtube? Let me check. Where are you guys? Uh Aditya is here. Okay Yeah, Mansri Ketna Arpita Any other questions that you may have Okay, so the youtube guys are with a small lag so far. So maybe they are still waiting for the same Okay No, no, okay Uh Yes, so, uh, okay, so i'm going to send these pdfs on the On the whatsapp group, you know, uh for for today's class as well. Uh Yeah Most of them I think they're only about seven or eight of you on the call right now So there are about six watching and one I have on sky Uh, I would have referred all of you to be on the google hangout So I could have spoken to all of you but maybe that's still not happening. So there are six viewers here Uh Okay Okay, our pita says no doubt. Yeah, so guys, here's here's the important key thing. Please go and visit So I'm I'm I'm leaving you actually five minutes early But you know over the time, uh, electrochemistry is slightly tricky chapter Uh, you know, uh, we will we're gonna get a lot of time to do a lot of problems on electrochemistry In fact, some conceptual questions is also something that I'm gonna do But what I also feel is that you guys, please have a look at the chapter today Or today or whenever you find time but earlier the better because since we have finished a class today If you're able to read through the chapter, uh, please underline anything that you still feel doubtful I'm going to spend one more class on electrochemistry and that would be the last class because I need to spend Uh time physically interacting with you in terms of the concepts and the problems Post which we'll actually start revision. Okay, uh, maybe we'll spend another one more class on but by the end One more class on hydrogen or chemistry in the service of man, but by the end of uh, November 15 or maximum by 20th November the week of November 15 We'll be done with our syllabuses because in other two classes we'll be done with everything that we have to work on Uh post which there will be only tests problems and uh, uh, and and and you know Discussions problem solving so let's not wait till problem solving comes because at that point if you're not having, you know There's generally a confidence loss that you might have on that, right? So if there are any doubt, let's do that before the uh Before we end up going to problem solving because there We we would like to focus only on the math part of it the numerical spot of part of it So that you know, we have a much more, uh, clearer clarity on the topics as such Okay, so, uh, I'm just going to pause here for a minute. Uh, Yeah, anyone who has any questions or else will Uh stop for the day Uh So you don't know how to take a log or you don't know, uh, what is the problem? Yeah Okay, so see basically whenever I say two square is equal to four or I say three square is equal to nine Then the when I take log of four to the base two I'm basically asking what power of two can I raise to To get four. So this answer here is two or here. I say what log log of nine to the base three I say what power of three can I go to to get nine? There's answer is also nine Now sometimes we might not have to do exactly a whole number for example 10 square and a cube root of this Okay, will be cube root of actually 100 Now cube root of 100 would be somewhere. So you see five cube is actually equal to 125 and four cube is actually equal to 64 Okay, now Cube root of 100 is going to be somewhere between four and five. So let's assume that maybe it's about 4.64 Okay, so basically what this means is that 10 to the power 2.3 2 by 3 because you know cube root of 10 square is 2 by 3 Right, so 10 to the power 2 by 3 is 4.46 So this means that I can actually take log of 4.46 4.64 to the base 10 and actually get an answer of 2 by 3 which is 0.66 Okay, so what it means is that any number tomorrow if you say sir take 2532 And I want to find log of this number with respect to 30 or forget even such a Good number that's it with 31. I can do that. I can say, okay log of 2532 to the base 31 Is equal to x now. How do you find this either? You know, there are log tables. There are calculator There are some log rules that you can do for example Like this can be written as log of 2532 to the base 10 divided by log of 31 to the base 10 Okay, now this answer would be somewhere around maybe This thousand right, so it's going to be somewhere around 3.5. I don't know. Yeah This would be somewhere around 1.2. So the answer would be, you know, maybe around 2.6 whatever Okay, so these this is the way that logs are found There is an entire log table process where all the logs can be found with 10 Maybe we can use log tables in some point of time, but log tables might not be directly given to you either the log values will be given to you or you will be You know, so they will directly give you for example log of 25 to 32 to the base 10 is 3.5 You just have to use that in the equations and solve the problem Okay, so log is nothing but what power can you raise something to so I can always raise any number to anybody's power You know tomorrow someone says 1.5. I have to find log of this with respect to 3.2 I can do that. I can say log of 1.5 to the base 3.2 I can always get a power for that Okay, and I can get an answer to this so 3.2 raise to x is equal to 1.5 Now let's find x this x can be found through lock table or through calculators. Okay, so that that can be done Yeah, is that clear does it work? Yes Yeah, now with this formula you simply have to write is that pH is equal to now the definition is given as pH equal to minus log of h plus Okay, this is to the base 10. So if pH is 7 It means that the h plus ion concentration is nothing but 10 to the power minus 7 because this minus sign comes here Okay, so 10 to the power minus 7 is h plus ion concentration Yeah, and when we say concentration this means moles per liter Is it clear is the concept here? Yes, yeah try and implement that at a couple of points, you know in in some problems We can do some problems in a citizen basis also whenever we have get time Yeah Okay, good. So uh guys good session, uh, I don't know how many if you could really Maybe is when I don't get to see you. I'm not sure, you know, what's happening around Uh, but okay, you have good time. Have a very happy Diwali to you and Enjoy the next two days or so You know, there are no classes on venus day on thursday also probably Yeah, maybe we might have an online. We'll see what we can do but have a good time and we'll see I'll see you next week in the Next class. Yeah, take care. Bye. Bye. Yes Thank you. Bye