Free Chemistry NEET Video Lectures for Electrochemistry

00:00:01 [Music] [Music] Good morning everybody. Uh today uh I'll start with uh electrochemistry. uh it is a branch of chemistry that studies the relation between electricity and u identifiable chemical changes where electricity can be cause or electricity can be output or effect. Now uh reactions involve electric char electric uh ch charge moving between electrodes or an electrolyte. Okay. So it deals with electrical energy and chemical changes. Now production of electricity from spontaneous chemical reaction. Uh a

00:01:02 large number of like metals uh chemicals like sodium hydroxide then chlorine etc are produced by electrochemical techniques batteries fuel cells etc. Here also electrochemistry is an integral part. Now uh reactions uh that are done with uh this electrochemical technique these these are basically you know in some cases these are eco-friendly and you know they don't generally produce u pollutions. Now also the signal transmission in living system is also uh known to have this electrochemical or

00:01:44 electrochemical in origin. Now uh when we uh talk about electrochemistry then the first thing that comes is uh you know conduction. So conduction means conduction of electrical charge across some circuit. Now uh basically uh here you know uh whenever we talk about conduction then different type of uh conductors are to be considered. One is uh like u you know this metallic conductor. Another is uh non-conductor or insulators. Another is semiconductor. And the fourth one is you know this electrolytic conductors.

00:02:33 Now uh electrolytic conductors means uh you know whenever we measure resistance across those materials like electrolytic conductors then uh you know this resistance is arising as a result of something which is a little bit different from what is observed in case of say uh metallic conductors. Now in metallic conductors what is happening that suppose uh this is a conductor. So you are applying some potential difference across this circuit. So electrons are transported from this side to that side.

00:03:24 this is transported from this side to this side. So uh so as such from outside there is no change in the material that is in the in the conductor. Now uh when it is the case of u electrolyte conductor the situation is a little bit different that that you have a solution okay and uh you are immersing two electrodes. So one is plus another is minus. And when you measure resistance that means some current is flowing across these two uh these two electrodes. Then what is happening that in this case you

00:04:09 know this ions which are there inside this solution. These are responsible for the for the carriage of charge from one place to another. Now so so uh different type of types of conductors like good conductor. So these are almost fully conducting almost fully conducting semiconductor. This is partially partially conducting insulator. These are not conducting. Okay. Now, uh I have just uh talked about this conduction through metal and conduction through electrolytic solution. Now what is the what are the

00:05:35 typical differences in this metallic and electrolytic conductors? So, so u in case of metallic conductor the electrons electrons are transported from one one position to the other and in case of say electrolytic electrolytic conductor ions are responsible. ions means when you talk about ions that means uh the substances which when are uh uh I mean dissolved in some solvent then they will produce ions and those ions against some applied potential difference they will you know move in a particular direction depending on the

00:06:40 direction of the applied electric field. Okay. So uh in this case in in case of metallic conductor so no transport of matter no transport of matter is there matter is there but in this case electrolyte or ions are transported these are transported. Now uh third difference can be like uh the resistance is almost proportional to temperature and in this case generally resistance resistance decreases with rise of temperature. This is just a rough approximation. I I'm not telling that exactly it is followed but this is a

00:07:41 rough approximation. And in this case no chemical change. But in this case chemical change is there at the electrodes. Chemical change at the electrodes. Okay. So these are the few uh I mean these are the differences between a metallic conductor and electrolytic conductor. Okay. So uh now let us move on to another thing which is common that uh that whenever we talk about uh this conductivity then or conductivity or resistance that that means when uh when you talk about this conduction of electricity then one

00:08:37 thing which is very important one parameter which is very important is the resistance of the of the medium. resistance. Now resistance it's uh it is basically proportional to length of the conductor and it is inversely proportional to the area cross-sectional area of the conductor. So for compound variation we can say R is proportional to L by A or we can write is equal to row L by A. It is row is basically the specific resistance or resistivity of the medium. Okay. Okay. So, it is the resistance of

00:09:32 1 m long you know conductor and if the cross-sectional area is unit then it it will be called as the corresponding resistivity. Now in in terms of conductance of a solution the generally used term is the conductance I mean I mean not it is not expressed in terms of resistance but it is expressed in terms of uh conductance. So conductance is nothing but inverse of resistance. So conductance is inverse of resistance. Okay. So what you can write? So conductance is equal to 1 by row into a by l. I mean from here we can write

00:10:31 like this. So this is this was specific resistance or resistivity and this is specific conductance or conductivity. So unit of resistance is uh oh and unit of conductance is oh inverse or m ho and in SI system it is semens. Okay. So therefore we can write conductance is equal to specific or conductivity into A by L or we can write from here we can write specific conduct conductance is equal to conductance into L by A which is basically a term which is given a new name cell constant. Why uh do we write sale constant? I am

00:12:27 coming to that. So specific conductance. So let us talk about unit of specific conductance. Specific conductance equal to conductance into cell constant. Conductance is cements into cell constant is L by A. L by A means length inverse. Okay. So that means cements if it is centimeter then centimeter inverse or if it is u meter then it is uh meter inverse okay so it is if it is uh meter then cements meter inverse if it is expressed in meter but it is si system so therefore it is better to better to use meter

00:13:40 rather than cmter okay so specific conductance is given a symbol kapa So kapa is equal to conductance into cell constant. Now let us come to the point why it is a cell constant. Now whenever we measure an unknown resistance okay whenever we measure an unknown resistance we generally use this uh celebrated uh witstone bridge principle. Now this widstone bridge principle is basically having this diagrammatic representation. So this is your unknown resistance R1 R2. You have a device that which is in most

00:14:45 of the cases is a galvvinometer source of electricity. So when the deflection is when it is it is there is no deflection means the bridge is uh balanced then ratio of these two this by this equal to this by this. So R1 by R2 is equal to R3 by R4. So from this R1 you can write R3 by R4 into R2. So if if this and this is a variable resistance. So you can you can have this balance of this uh galvvinometer deflection. there is balance of this bridge when I mean at at some appropriate value of R2 then you

00:15:46 can at the balance point balanced point okay so uh this way you can find out the unknown resistance R1 okay so u now u when it is solution solution means you have an electron prolytic conductor other than I mean it is not uh common this metallic conductor or some other kind of conductor then you have these two electrodes and you have you you have to measure the resistance across these two electrodes. Okay. So across these two electrodes means you need to have one electrode over here another electrode over here and then

00:16:37 this two wires are basically these two wires. I mean you have to connect this this one this is represented like this your your electrolytic cell is represented like this. Okay. So this is one unknown resistance say R1. So you place this over here. Okay. So your this diagram looks like this one. So you have to replace this with this one. Okay. Now there is a little bit uh difficulty in measuring this this resistance or conductance of this electrolytic conductor. This is because of the fact that as I mentioned

00:17:23 to you earlier while discussing the difference between a metallic conductor and an electrolytic conductor that is there is a there is some chemical change at the electrodes. Okay. So, so since there is a chemical change uh at the electrode then then during measurement of the resistance of this particular sale then the the the characteristic of this of this material is getting affected. Okay. So therefore that's why you have to construct a cell like this that you have your unknown uh solution kept over

00:17:59 here electrolytic solution kept over here you deep to electrodes and then you measure resistance but while measuring resistance you have to be very careful that in this case in most in in most of the cases when you use this widstone bridge then you supply a DC current okay in that case there is no problem in the measurement of the unknown resistance but the moment to use DC current for this then there will be electrolysis or various electrode processes. So electrode is getting affected and if the

00:18:34 electrode is getting affected then you are not going to get the right value of R1. So in this case what you have to do you have to use you have to make use of a different technique but the same bridge principle but here in place of a DC supply you have to use AC. So AC means it is a cosine profile as a function of time in this case intensity of the field and this is your time. So what is happening that in the say first first positive half cycle if this electrode is positive then the other electrode is negative in the next half

00:19:23 cycle over here the polarity is reversed this becomes minus this becomes plus and if this alternation is symmetric that is area under the carve over here and area under the carb over here. These two match. Then then what is happening? Uh then in the positive up cycle whatever is generated over here and also over here the reverse is generated. But the point is so therefore what is happening if a simple electrode is used then the accumulation of various material is there especially when you use water as a

00:20:01 solvent then electrolysis product of water that is oxygen and hydrogen these are produced in equivalent amount on each of the electrodes. So electrode will be affected electrode will be affected in the sense that it will be covered with those gases. So therefore characteristic of the electrode will be changed. So therefore in this case if you use a platinized platinum electrode. Platinized platinum electrode means it is a smooth platinum plate on which this finely divided platinum metal particles

00:20:39 are deposited on this and these are acting this can act as this can act as a catalyst for the recombination of oxygen and hydrogen to produce water. So therefore electrode will be electrodes will be you know freed from these accumulating gases. So therefore electrode characteristics will not be changed and and and as a result of which you can you can measure the actual resistance across these two electrodes. So basically you are putting putting this cell over here. That's why the sale constant is coming uh over

00:21:16 here. So cell constant is nothing but it is the ratio of the length length with between these two electrons. This is your L and A means this is your A. This is the area you are talking about. Okay. So therefore L by A is the cell constant. Okay. So this way uh so uh this way you you make use of this AC supply to measure the resistance I mean the conductance of the of the of the cell that means conductance of the cell which is containing your required material. Now how do you how will you will you

00:21:57 identify this balance point of this whe bridge? This is done in a little different way. Here this frequency of AC is about say 500 to say 1,000 or similar values are there and when the bridge is balanced that means you change your R2 in or you you uh you adjust your R2 in such a way that uh that if you put a headphone over here then minimum sound will be will be uh you know will be here and therefore therefore you will be uh you will be confir you you will you will get a confirmation that this uh bridge is

00:22:40 balanced and at the balance point whatever values of these are there I mean R3 R4 and R2 is there use make use of this to find out the value of your unknown resistance that means in turn you measure the the conductance of your unknown solution okay so uh so therefore so what is the The expression that you generally use is specific conductance is equal to conductance into cell constant. Okay. Now let us have some idea about various conductors uh various materials as far as their conductance value values are concerned.

00:23:30 So if you uh if you consider materials like materials and their conductance it is in cement inverse. Okay. So say for example copper copper metal its value is about 6 into 10 ^ 3 silver its value is about say very close to this value I mean copper value okay glass its conductivity is very low it is about 1 into 10 ^ -16 pure water it is about about 4 into 10 ^ -5 for example uh if it is 0.1 molar HCl its value is close to four geranium it is about two. So you see that if you think this think about these two

00:25:09 and think about this metallic conductor then it is its value I mean this conductivity is very high in case of pure water it's very low but but it is much better than glass or some other non-conducting material in case of you know this.1 molar HCl it is about 10 ^ 5 times more than that of pure water. Okay. So, so why this is uh this is happening? I mean I mean the clearcut answer is that in.1 M HCl you have H+ and Cl minus ion. These are responsible for the transport of electrical charge from one position to the other. In case

00:26:03 of pure water, it is fibly ionized. Water is fibly ionized to H+ and O minus very fibly ionized. So therefore, since the ions present in water in pure water, so these are very less in number, therefore conductivity is quite low. Okay. So this gives you some idea about the conductivity of of various materials. Next next we'll uh we'll uh move on to another quantity which is called the molar conductivity. Molar molar conductance. Molar conductance is the conductance of a solution which is

00:27:10 having one molar substance dissolved in water and it is measured measured with two electrodes. Those are separated by those are uh these two electrodes are separated by unit distance 1 meter. Okay. and uh whatever conductance value you are getting it is called the molar conductance. Okay. So uh molar conductance is basically given in notation lambda m and lambda m it is expressed as expressed as kapa by concentration where lambda m is having unit cements m²ared mole inverse where capa is expressed in cement m inverse

00:28:16 concentration is mole per m cubed. Okay. Now uh if we would like to know why how how this molar conductance will depend on concentration of the of the material. But before that let us have some idea of how simple conductance will will vary with concentration and other factors. Okay. So before that let us have some idea. So conductance as I mentioned that it is due to the due to the transport of transport of ions across the electrons. So therefore ions means ions means things are to be considered are

00:29:17 basically you know number of ions. So that means if more number of ions are there in the material then it is expected that that the amount of charge that will be transported across the electrons will be more. So number of ions is very important. It is an important factor. Then charge charge of the ion. Okay. Charge means suppose you have you have say M plus say M1 plus say M2 2+ and say M3 3+. Okay. Suppose you have M1 ion with uniositive charge. Say M2 ion, M1 ion, M2 ion and M3 ion with bipositive charge and M3 ion with

00:30:24 tripositive charge. That means one ion contains three unit charges. This ion contains two unit charges and this ion contains only single charge. Then suppose if this ion is transported across this two electrodes from here to here say M_sub_1 plus then only one unit of charge will be transported from here to here. If M2+ is transported 2 plus is transported from here to here then if the other factors are remaining same then you'll be saying you'll be you can you can tell that that in the same

00:31:04 time or in the same duration suppose these two are reaching this this side in same time like t1 time and here also t1 time then the amount of charge that is carry forwarded from here to here it will be double for this it will be triple for this. So therefore charge of the ion is very important in the conduction process. So therefore conductance will also depend on the charge of the ions. And next one is the speed of ions. Speed of ions. Suppose you have you have two ions. Say ion one and another is ion two.

00:31:53 Say this is also uni positive. This is also uni positive. But the thing is that suppose that it can swim faster than this one. That is its mobility is more than this one. then in in same time interval the amount of charge effectively it will it will transport more charges than this one because it is it can move faster than this one. So therefore that's why these are the three important parameters important factors that are needed to be considered while you know while discussing the conductance of a solution. Okay. So

00:32:33 therefore therefore uh therefore when a solution is diluted what do you expect to have? Suppose you have one one molar suppose you have say for example uh one molar say NaCCl solution suppose you dilute to say 10 ^ minus 2 molar and then you measure its conductance okay some value you can expect with the help of your device that is you know this using wit stone bridge uh principle. So so some value you you can expect that is maybe say for example x is the is the measured conductance. Now now you dilute it to say

00:33:35 half into 10 ^ -2 molar. Okay. Initially it was this much. Now it is half into 10 into the minus2 m. Then conductance is expected to be expected to be reduced. Why? This is because of because of the fact that the number of ions okay number of ions that is present in a given volume it is now reduced. Okay. number of ions is reduced and since number of ions is reduced therefore conductance is expected to be reduced. So go back to the formula specific conductance equal to conductance into cell constant.

00:34:21 So cell constant is remaining same. So what you are doing you are diluting the solution. So what happens to specific conductance? What is specific conductance? It is the conductance of a solution which is placed between two electrodes unit distance apart say 1 m apart and also the electrodes are having 1 m square cross-sectional area 1 m square cross-sectional area. So, so if you dilute it initially, say for example, X number of say ions, say for example, say X prime number of ions were present in this unit cube. Now

00:35:12 if you have dilute it then this becomes X prime by two. Okay. So xind by 2 means your number of charge carrier is reduced reduced to half. So number of ions is reduced then charge carried by ions charge on ions no change and speed of ions. This is also also al also you know you can consider this that this one is also remaining unchanged. So therefore since the number of ions is reduced specific conductance decreases cell constant is fixed. So therefore conductance is expected to be reduced. Okay. So therefore therefore again come

00:36:08 back to again come back to molar conductance. So that that we we started to talk about and in between we we wanted to you know learn about how conductance is dependent on various factors and we have you know explained to you that these are there are the major I mean three factors one is number of ions another is charge on the ions and speed of the ions. So molar conductance is lambda m which is nothing but your specific conductance kapa by c where c is mole per meter cube and kapa is cement's m inverse. Now if

00:36:52 you now plot if you now plot molar conductance that is lambda m with square root of concentration. It has been found that for the It has been found that for the strong electrolyte the curve follows like this that is if you dilute it in this direction if you dilute it then molar conductivity increases. So why is this so why mar conductivity should uh should increase when you you know when you dilute the solution. Now, now again lambdal lambda m is your kapa it is your conductance okay then specific conductance

00:37:54 and then inverse of sale constant okay that means a by l okay okay so the idea is that you have to place your solution. You have to place your solution against or in between two electrons that are separated by unit length. Unit length L is equal to 1. Okay. So therefore if your volume of the solution volume of the solution is V then effectively area of the electrode is nothing but V is equal to A into 1 because A is the area because you have to place your entire solution in between two electrodes. those are

00:38:54 separated by separated by unit length and your there is no restriction of the of the area of the electrodes. So therefore area is freely changeable depending on the dilution of the solution. Therefore you can write from here v is equal to a. So therefore from here you can write lambda m is equal to capa into volume. Okay. So therefore how does lambda m change as a function of dilution. So when you dilute means volume is increasing. Okay. And what is going to happen to kapa? very simple that as I already

00:39:45 explained to you here that when you dilute then kapa is reducing. So therefore there are two opposing factors one is kapa which is reducing as a result of dilution and volume which is increasing as a result of dilution. So what is going to happen that your ultimately it has been found that the effect of change of volume is much more than the effect of dilution of I mean effect of lowering of kapa. So therefore in effect lambda m is found to increase. So therefore that's why lambda m as a function of square root if you plot it

00:40:30 it it follows a trend like this. But only thing is that important point to note is that this type of linear dependence this type of linear dependence is observed for strong electrolyte. Strong electrolyte strong electrolyte means the electrolyte which is which is completely ionized when you dissolve it in water. Okay. But uh the situation is not so easy. I mean it is not like that like a linear dependence for a weak electrolyte. Okay. So for weak weak electrolyte what is happening? Let me draw it again in a in another piece of

00:41:15 paper. For weak electrolyte, for weak electrolyte, uh the plot you know it is square root of C and this is lambda M. It follows a trend like this. Whereas the strong electrolyte follows like this. Say this is CH3 CO and this is say for example KCL. So this is quite you know understandable. I mean why this is increasing like this. But in case of weak electrode you see that as you dilute it there is not much perceptible change in the higher concentration range. Say for example u if your concentration is in mole

00:42:14 per liter and the value cements cm² mole inverse then say for example it is say about 200 and here it is say for example 0.2 0.4 these values are 0.4 okay and 0.2 two. Then you see that in higher concentration region it is almost flat. Okay, it is it is following the same trend as your you know this axis it is parallel to almost parall to x-axis but when you decrease the concentration you know it's it follows a trend like this and in very low concentration region it steeply rises. So why is it happening?

00:43:06 This is something strange. Uh why strange? Because it is unlike this strong electrolyte. This is following a different trend. Why it is like this? Now one thing that that you should take into account that this CH3 CO it's a weak electrolyte. So it is not completely ionized. So if you dilute it then its ionization increases. So that means CH3 CO it is mostly in this form CH3 C minus. So degree of dissociation if it is alpha then 1 minus alpha then alpha then alpha. So therefore degree of dissociation since degree of

00:44:12 dissociation is very small in moderate concentration range. Therefore you know number of charge carrier that is you know less in this region. The moment you keep on I mean the moment you increase the dilution that means if you add more of water then the degree of dissociation I mean the amount of dissociation increases and therefore therefore what happens that whatever factors were there like like you know lambda m is equal to kapa into v. So V factor is there V increases at the same time you know this

00:44:50 capa is also increasing because if you dilute it then number of ions number of charge carrier increases. So total number of if charge carrier increases means your kapa although there is a dilution effect but the effect of this increase of charge carrier is coming into action and as a result of which a nonlinear dependence of you know nonlinear dependence of this uh this lambda m versus root over cpl plot is there. So in case of strong electrolyte you know this u for strong electrolyte lambda m that is the uh

00:45:35 molar conductance follows a trend like this lambda m0 plus a square root of c where lambda m0 is a constant quantity and you can understand from here that that if if you go close to zero concentration that is infinitely dilute condition then then whatever lambda m value you are expecting that is nothing but lambda m0 so it is nothing but the value of lambda m extrapolated to zero concentration okay now so therefore this is called the limiting molar conductance or molar conductance at infinite dilution

00:46:25 Molar conductance at infinite by infinite dilution. One can understand like this that it is a state of dilution at which if you further dilute the solution there is no perceptible change or there is no further change in the conductance value of the solution. So that is called the that is called the um state of infinite dilution. So therefore if you have a strong electrolyte if you plot like this then you have got certain points. So so these are all measurable things. So you measure and then you

00:47:18 extrapolate just because the trend is linear. So you extrapolate. So wherever it is extrapolate wherever it is cutting the y-axis is nothing but lambda m0. So, so for for uh strong electrolyte the job is easy easier that you can measure the the value of lambda m at the infinite dilution condition. But the problem comes when you have you have this uh this weak electrolyte that like acidic acid then you cannot apply you cannot apply this uh uh this extrapolation procedure to find out the find out the

00:48:01 infinitely dilution condition this lambda value. Okay. Now, so in that case what uh you can do? So it was first proposed by kolas long time back that uh so kas and long time back kolas it is called the kolas's law of independent migration of ions. So what was the observation? observation was like if you measure like lambda m0 for say KCL and then lambda m0 for ncl and then again if you measure lambda m0 kr lambda m0 navr I mean if you if you Take a difference of lambda m0 for KCL and NL. Then KBR NABR

00:49:24 or uh lambda M0 KI 0 N AI. It is found that its value is uh say close to 23 simmons cm² mole inverse. Okay. At some given temperature. Okay. In the same way, lambda m 0 n a br minus lambda m0 n a cl is equal to lambda m0 kbr minus lambda m0 kl and that comes out to be close to two uh semens cm² mole inverse that is your molar conductivity at infinite dilution if you take the difference it is found that this is following like this. So this is a very strange behavior that for electrolytic conductor electrolytic uh when we talk

00:50:34 about the electrolytic conductance then then um then it is uh it is very strange uh that KCL minus NaCCl KBr minus NABR Ki minus Ni so you see that here these coions here also coions You see we if we if we want to take the difference of this lambda zero with same coins then this difference k plus na plus this is k plus na plus this is k plus na plus this difference is almost same in the same way uh you know this coion sodium same this co potassium same so Br minus cl minus l they are following the same

00:51:23 trend so this is a strange behavior happen. So, so it is proposed that that at infinite dilution something is happening. What is exactly happening conceptually that I already have explained to you or or discussed that that the conductivity of a solution is dependent on the number of ions, charge carried by ions and speed of ions. So when you have reached the state of infinite dilution condition then the number of ions present in unit cube it is also fixed. Then charge on the ion it is already fixed. Only thing is that the

00:52:02 speed of ions. Now speed of ions is is an important factor for the transport of electricity from one position to the other. Now if the speed of ions is not changing any further due to dilution as I mentioned to you that state of infinite dilution is nothing but that can be that can be stated in terms of conductance that if you further dilute the solution it does not bring in any change of the conductance of the solution. Therefore no further change is happening even if you dilute. That means when you dilute a solution a a say a

00:52:37 concentrated solution then suppose initially say there are there are two ions like this. So they are interacting one with another and this is that that will be a natural consequence because this one is charged this one is also charged. So there will be charge charge interaction and many other factors maybe solvation and other factors are also important. So when you dilute means it is separated. So interaction between this ion and that is expected to be reduced. Okay. So therefore therefore uh if this ion is

00:53:13 moving if they are in close proximity these two ions are in close proximity then the movement of this ion is expected to be affected by the movement of this one and vice versa. But if you keep on diluting then a situation will be reached when this ion and the other ion they are so much separated that practically there is no effect of the interionic attraction or or or the influence of this ion on this one. So therefore the ions can move freely. So when ions can move freely that means they can freely contribute towards the

00:53:50 conductance of the solution. Okay. So that's why at infinitely dilute condition this one is independent this one is independent. So their difference their difference in conductance or molar conductance is also also independent I mean it is not also dependent on the co-ion because coions are also separated from one I mean from from this one this ion or this separated a lot. So that's why that's why the difference is nothing but the but the difference uh I mean here KCL minus NL KB minus N they are

00:54:24 following the same trend. So that is called the uh that is called the cold resis law of independent migration of an and basically basically you can write at infinite dilution lambda m 0 kl is nothing but lambda 0 m k plus lambda 0 m sorry cl minus okay so in the same way If this this um uh you know electrolyte is um having more than one ion so accordingly you need to have some stoometric coefficient to be included over here. Okay. So, so therefore, therefore um therefore um basically at infinite dilution condition

00:55:15 each ion will contribute each ion will contribute to a definite extent toward the toward the total conductance of the solution toward the total conductance of the solution and uh let me uh write some numbers I mean some of these uh numbers for different uh ions few ions I have uh I will just uh uh write for you. So lambda 0 it is semens cm² mole inverse for h+ it is 349.6 6 for H minus it is 199.1 K plus it is 73.5 Cl minus it is 76.3 so you see that that for different ions this contribution this contribution is

00:56:11 is different okay so therefore therefore uh see this independent ion migration this concept has to be applied in in in in finding out in finding out the uh the conductance uh conductance of the I mean um in finding out the the lambda zero lambda this lambda m0 for weak electrolytes. I mean direct you know direct uh finding out of this uh lambda m0 for weak electrolyte is not possible is not possible although that is possible for strong electrolyte in that case indirectly you have to find out the

00:56:54 contribution of this okay contribution of these uh uh these ions individual ions and then you can find out you can find out this u this lambda m0 so uh this much for today so Um we will take up this issue. I mean uh how to find out I mean um how to make use of this lambda m0 for weak electrolyte in finding out in finding out uh um some important u quantity important quantity important characteristic quant quantity of the weak electron. So what we have learned today? So uh we started with this uh

00:57:35 conductance. Okay. Now we have talked about uh this metallic conductor then some idea of the you know basically this uh insulator then this semiconductor we have just given some example that's it and then we have come we have we entered into this electrolytic conductor because in electrochemistry this uh this is relevant in electrochemistry. So electrolytic conductor we have uh we have entered into and the cause of this um this conductance we uh discussed and then we we have used this uh the concept

00:58:16 of simple chemistry concept to to know how this uh you know uh this conductance and specific conductance these uh these will uh will you know vary as a function of concentration. So uh and and we we try to understand this um this variation of molar conductance as a function of concentration for strong electrolyte and for weak electrolyte the direct determination of this uh lambda m by the by this u graphical extraolation is not possible. So in that case we need to find out the some some you know

00:58:54 roundabout way in in in getting the value of lambda m0 for weak electrolytes and and we'll take up this application of this lambda m0 measurement for for weak electrolyte in the next class. So till then that's all for today. Thank you.