Electrochemistry in Just 15 Minutes 🔥 NEET 2026! Wassim Bhat

Hinzugefügt: 2026-05-03

[00:00:00]Hey students, the first topic that is Daniel cell. You know in your Daniel cell we use two electrodes. One is your zinc and one is your copper. Zinc behaves like the anode. In the Daniel cell copper behaves like the cathode.

[00:00:13]The moment of electrons in the Daniel cell is from anode to cathode. The direction of current in the Daniel cell is from cathode to anode. In the Daniel cell there are two moles of electrons which are exchanged between anode to cathode. Right? And this is how you exactly represent your Danielson cell.

[00:00:32]In the middle you have got a solid bridge. On the left side you are writing the anodic part. On the right side you are writing the cathodic part. Perfect.

[00:00:39]What happens when the Danielson works?

[00:00:42]The thickness of the zinc rod decreases.

[00:00:44]Thickness of copper rod increases. Now what is a salt bridge which we use in the Daniel? Salt bridge it's basically you know it. It is the inverted utype tube which contains inert electrolyte mixed with gelatin. And what do we get at the end? We get a jelly- like paste which is fitted in that inverted utype tube. Now what are the functions of the salt bridge? You already know salt bridge. It completes the internal circuit. It maintains the electrical neutral as well. Now my dear students the inert electrolyte which we use in the salt bridge what kind of behavior it should show. My dear students, the whatever inert electrolyte you are using in the solder bridge, remember one thing, the kion and the anion of the inert electrolyte, they should have same ionic mobility. That means their speeds should be the same. The kion and anionic speeds of the inert electrolyte they must be same. Then only the liquid junction potential will be avoided. Okay, my dear students, how do we represent the cell?

[00:01:48]Well, you know in the middle it's a salt bridge. On the left side of the solid bridge, we always write the anode. On the right side, we write the cathode.

[00:01:55]Right? Okay. And this is how you exactly represent your Daniel cell. Right? See your zinc gets converted into zinc dipostor in the anodic part. In the middle is the solid bridge. On the right side, you have got cathode, right? At which reduction takes place. Copper dipostor gets converted into copper solid. Perfect. Before going ahead uh I would be sharing the PDF of this particular session as well and it will be shared in the telegram t.me/w a ss i m s i r c h e m. Right. This is the telegram channel on which I shall be sharing the pdf of this particular chapter. Okay. Perfect. Moving on to electrode potential. How do we define the electrode potential? It is the potential difference that exists between the rod and the electrolytic solution.

[00:02:42]Right. And when this electrode potential is measured under standard conditions which involves pressure 1 bar uh concentration 1 molar temperature constant generally 25° centiggrade at that point of time whenever you measure the electrode potential that's what you call as standard electrode potential which is represented by E not now this standard electrode potential is of basically two types. One is called as standard oxidation potential SOP and another one is what you call as standard reduction potential that is SRP. Now for an element SOP is always equal to minus times its SRP. Now my dear students what is the significance of the standard electro potential? Do you remember more the standard oxidation potential of a specy more is its tendency to undergo oxidation better the reducing agent more the reducing power. Similarly more the SRP of the specy more is its tendency to undergo reduction. Better the oxidizing agent more will be its oxidizing power.

[00:03:41]Right? And similarly you would have heard about the standard hydrogen electrode that is taken as the reference electrode whose SOP as well as SRP both the values are taken as zero. Right? As per reference now talking about the emf.

[00:03:54]How do you exactly define the term emf?

[00:03:56]Emf is nothing. It is just the maximum potential difference between the two electrodes when the cell is not in use.

[00:04:02]Right? And how do we calculate the standard emf? E not cell. It is E not of cathode minus E not of anode. E not of cathode means SRP of cathode. E not of anode means SRP of anode. Right?

[00:04:14]Similarly, moving ahead, there are few results which you need to remember and from these results questions are directly asked. First result is between delta G and E cell. My dear students, delta G for the cell is equal to minus NF cell where N represents number of moles of electrons exchanged. F represents the faradase constant and E cell is basically your emf of the cell.

[00:04:36]Now when you calculate the standard Gibbs free energy change for the cell it is minus NF a E not cell perfect. Now the most important part of this chapter that is Nest equation right. How do we write the Nest equation? First of all in this format E cell is equal E cell is the EMF of the cell under non-standard conditions. E not cell is the standard EMF minus 2.303 RT / NF log of QC where QC is the reaction quotient. Right? And my dear students the modified form of nerist equation which we use in the equations that is E cell is equal to E not cell minus 0.0591 divid N log of QC right now you know you can make millions of galvvinic cells right you just have to take two electrodes connect them externally and internally you will be getting a galvanic cell. Now what is the condition for that galic cell to be working my dear students for the galvinic cell to be working for its cell reactions to be spontaneous delta G for the reactions should be negative or you can say emf of the cell should come out to be positive and my dear students when the galic cell works you know a stage arises that's what you call as equilibrium stage at equilibrium the potential difference between the electrodes that becomes zero and cell at that point of time does not work so at equilibrium your E cell as well as delta G for the cell that comes out to be zero. Okay. Now the point is how do we calculate the oxidation potential and reduction potential of the half cells under non-standard conditions or I can say how do we calculate the oxidation and reduction potential of the electrodes under non-standard conditions. For that purpose again we'll be using the earnest equation only. Have a look. Oxidation potential of the halfell is equal standard oxidation potential of the halfell minus 0.0591 0591 divided by N and log of QC.

[00:06:25]Similarly, how do we calculate the reduction potential of the half cell? E is equal to E not minus the same result.

[00:06:33]Right? And how do we calculate the emf of a complete galvvinic cell of a complete cell under non-standard conditions? This is the result. E cell is equal to E not cell minus 0.0591 divided by N log of QC. Now you must be thinking how this QC expression is to be calculated. For example, this is your balanced chemical equation. How do we write its QC expression? Before writing the QC expression, you should know whenever you see any reactant or product in the aquis phase, right? Its ectoass is taken as its concentration. If you see any reactant or product in gaseous state, its ectoass over here will be taken as its partial pressure. If you see any reactant or product in pure solid or pure liquid phase, their ectoass is taken as unity. Right? Now, QC is equal. Start with the product.

[00:07:19]This is the product. So it's in solid form nothing to do with this. Now moving on to this product right it's in aqua state. So concentration of d raised^ n4 divided by concentration of a raised^ n1 is in gaseous phase partial pressure of b raised^ it to stoometric equation that's n_sub_2. Now one more thing that's important what is that concentration cells. In concentration cells what do we do? We use two same electrodes. Right? If we are using two same electrodes that means e not cell has to be zero. So whenever you see any complete cell involving two same electrodes first thing that should come into your mind that is its e not cell will be zero right same electrodes are used now this concentration cell is basically of two types one is called as electrolytic concentration cell one is called as electrode concentration cell in electrolytic concentration cell what do we have in electrolytic concentration cell we keep the concentration of electrolytes in both the containers anodic container and cathodic container as different due to which emf gets generated. Similarly, in electrode potential in electrode concentration cell what do we do? We keep the partial pressure of the electrodes different by means of which emf gets generated and once emf gets generated cell automatically starts working. Now these are again two important points which you need to remember. Reduction potential of the half cell reduction potential of the electrode is directly proportional to the concentration of electrolyte kept.

[00:08:42]If you keep the concentration of electrolyte more in the container, the reduction potential of the overall electrode will be more and if less then reduction potential will be less and inverse is the relation with the oxidation potential. Right? If I move ahead and talk about few more things that is thermodynamics of the cell. How do we calculate delta G for the cell minus NF cell? Do you know it? Right?

[00:09:05]How do we calculate delta S? Entropy change for the cell reaction is equal to NFD upon DT where DE upon DT is called as temperature coefficient of the cell.

[00:09:15]Right? And if you got delta G for the cell, if you got delta S for the cell, you can calculate delta H as well. This is the relation, right? You know delta G is equal delta H minus T delta S. From that particular relation, you can calculate delta H for the cell as well.

[00:09:29]Now guys, talking about products of electrolysis, right? When you do the electrolysis of different electrolytes, right? What are the products of electrolysis which you get at anode and cathode? Three main I have mentioned over here. You're supposed to remember them. When we do the electrolysis of molten ACL at cathode sodium gets deposited at anode chlorine gets chlorine gas gets liberated. NaCCl aquis at cathode hydrogen gas gets liberated.

[00:09:54]At anode CL2 gas gets liberated. Aquis CSO4 right when you do its electrolysis at cathode copper gets deposited at anode O2 gets liberated. Right? And over here during the electrolysis of all these three electrolytes do remember the electrodes are basically your inert ones. Okay. Now moving on to Faraday's first law of electrolysis. What paradise first law of electrolysis is all about.

[00:10:21]My dear students is a very simple thing.

[00:10:22]Since during electrolysis either metal gets deposited or gas gets liberated.

[00:10:27]Right? Now the amount of m the amount of substance deposited or liberated at any electrode that is directly proportional to the charge which goes into the solution. More the charge going into the solution more will be the amount of substance either deposited or liberated at the electrode. And this is the result by means of which you can calculate mass of substance deposited or mass of gas liberated at a particular electrode.

[00:10:53]Similarly, this is the result by means of which you can calculate the moles of substance deposited or liberated at a particular electrode where E stands for the equivalent mass of the substance. I stands for the current which goes into the solution. T is the time duration in which the current goes into the solution. Similarly, what is your Faraday second law? Okay my dear students Faraday's second law says that whenever you have got two or more than two electrochemical cells or I'll say it like this whenever you have got two or more than two electrolytic cells containing different electrolytes connected in series do remember the gram equivalence deposited or liberated at every electrode will be the same right whatever electrode you have gram equivalence depos or liberated every electrode is definitely going to be same now my dear students Over here you would have seen this n factor right? How do you calculate n factor of different substances? Whenever you see a balanced chemical equation like this right for example you have to calculate n factor of a it will be electrons exchange 12 divide by it to stoometric equation. So 12 12 x2 this is going to be 12 / 3 this is going to be 12 / 6. This is how you exactly calculate n factor of different substances in a complete balanced chemical equation. Number of electrons exchanged divide by its chrometric coefficient. Now talking about few more terms about the conductance part. The first thing is the resistance.

[00:12:17]Resistance of the conductivity cell.

[00:12:19]Resistance of the electrolytic conductor. Right? It is something which you all must be knowing. It is the obstruction in the flow of the current.

[00:12:25]How do you calculate this resistance? It is nothing but R is equal to row L by A where L is the distance between the electrodes and A is what? And A is the area of cross-section of that part of the electrode which will be inside the electrolytic solution. Then you have got resistivity. This particular formula you have got conductance which is defined as inverse of resistance right it its unit is simon particularly conductivity 1x r into l by a this l by a particularly is called a cell constant right and the units of kapa over here is simon cm inverse molar conductance how do you define the molar conductance it is defined as the conductance shown by one mole conductance shown by the solution conductance shown by the electrolytic solution when one mole of electrolyte is present in in a given volume of solution. Perfect. This is how you calculate molar conductance. Molar conductivity kapa multiplied with thousand divided by normality. Right?

[00:13:18]When it's to be calculated in simon centime square per equivalent. Now you should remember with dilution with dilution molar conductance equivalent conductance they increase but conductivity it decreases right?

[00:13:31]Conductivity decreases and it's valid for both weak as well as strong electrolytes. And the last topic which you all must be knowing that's gold rush law. Gold rust law says that the equivalent conductivity at infinite dilution of an electrolyte is basically the sum of sum of their ionic conductivities. And this is how you write the statement. And its main application is to calculate the degree of dissocion of a weak electrolyte. How do you do that? Molar conductance of the weak electrolyte at a given concentration divide by molar conductance of the same electrolyte at infinite dilution. Similarly, molar conductivity of a sparingly soluble salt is nothing but capa multiplied with,000 divid by solubility or marity when you have to calculate simon cm² per mole. My dear students this was a very quick revision of the chapter electrochemistry I believe it'll be properly clear to you. Now I have already taken its marathon right from the marathon it would have got cleared in detail and from this particular session I believe all the important things which I have to share with you I have conveyed them all over here. So with this I'll be taking a leave. I'll keep on coming coming up with all these such sessions and for those sessions please and please do subscribe to this particular channel and do hit the like session on hit the like button on this particular session as well. So with this I'll be taking a leave take care God bless you all and love you all guys. Bye-bye.