 Okay. Hello, everyone. Hello, who are all there? All of you have joined? Okay, Sanjana Rittik Visist Purvik Koshal. Okay. So today, like as I said yesterday, Shruti is also there. Hi. As I said yesterday, today we are going to start our revision classes for this JEE mains. We are going to discuss chemical equilibrium. Equilibrium. Okay. See, actually, you all have done this chapter once. Okay. So we will not go into that detail. Okay. Like every derivation and all, we will not see. Okay. If you have any specific doubt, then you can ask me. You can stop and you can text me over this portal. You can ask me any specific doubt if you have. Okay. But I'll give you a brief, you know, brief introduction of this chapter. Brief formulas. I'll give you what all formulas are important and the important point that we have here. Right. Okay. So and then we'll solve, we mainly focus on problem solving. Okay. We'll try to understand the concept with questions itself. Okay. Since we don't have that much time. Right. So with problem only, we'll try to understand the concept mainly. Okay. So like you see in this chapter, the most important, you know, the portion we have, that is Lee Chatelier's principle. Okay. You will definitely have one question. Like if you see any previous year paper, Lee Chatelier principle based on this, you definitely have one. You will definitely have one questions. All of the questions related to KC, KP and all that you can do easily. It is not that much stuff. Okay. So basically this chapter is a bit easier. Okay. And then the other chapter. Okay. It's a bit easier chapter, basically. So, okay. So I think all of you have joined Sharania, Shweta, Rishali, Sriram, Swannarya. Okay. So let's start with this chapter. So what is an equilibrium? Equilibrium is what when like in physics also we define equilibrium and the forces are balanced. Like, no, when all the forces acting on a particular object, if it is balanced net forces zero, then the object is said to be in equilibrium. Right. That is also one of the definition of equilibrium. But since this is chemistry and we are dealing with chemical equilibrium, chemical reactions into it. So we have to understand how do we define equilibrium in any chemical reaction. So first of all, when we talk about equilibrium, for equilibrium, we require two opposite processes, right? For equilibrium, we require two opposite processes, processes, right? Two more important things we have over here, that whether it is given in the question or not, you have to keep this in mind that equilibrium is only possible whenever the process is going in a closed vessel. If it is open, then the equilibrium will never maintain, right? Like I've told this thing in the class also, the vessel must be closed wherever the reaction is taking place. It must be a closed vessel, then only equilibrium possible because we have to conserve the amount or the mass of the reactant that we are taking. Because when reactant converts into product and some of the mass, if it is open vessel, it is going into the atmosphere, then the possibility of equilibrium will not be there, right? Two things. So basically, like we say, when we talk about the direction or direction in which the reaction may proceed, there are basically two types of reaction, right? Two types of reaction we have. There are various other classification of reactions. We are talking about only in terms of direction we are talking about, right? So two types of reactions we have. One is irreversible reaction, irreversible, and the second one is reversible reaction. Irreversible reaction always goes into one direction, from left to right, reactant to product, okay? Reversible may go in both direction, like left to right or right to left also means into the forward direction and backward direction also it's possible, right? So in this chapter, we are mainly discussing or we will discuss about only reversible reaction because equilibrium is only possible in case of reversible reaction. If the reaction is irreversible, unidirectional, in only one direction the reaction is going on, then the possibility of equilibrium will not be there, okay? So first thing is this. In this, we are dealing with reversible reaction, okay? And the condition of equilibrium is what? Rate of forward reaction, rate of forward, I hope you all know these things, right? Rate of forward reaction is equals to rate of backward reaction, rate of backward reaction, okay? So I will go a bit fast over here. Backward reaction, rate of forward reaction is equals to rate of backward reaction, then only the equilibrium will be maintained. One thing you must keep in mind, at equilibrium, if you feel any point important, you may write it down, okay? At equilibrium, the reaction never stops, right? If the equilibrium has been achieved, it does not mean that the reaction is not going on, okay? It is going on but with equal rate, okay? The rate at which it is going into the forward direction with the same rate, it is coming into the backward direction. It is going to be the backward direction only, right? So reaction never stops at equilibrium, okay? So the next thing here, that is, suppose, there is one law over here, that is, let me take one reaction, suppose, A plus D gives C plus D, right? So for this, a law we have, that is, law of mass action, mass action, and this suggests that the equilibrium constant, Kc, is equals to the concentration of product divided by the concentration of reactant. This is equilibrium constant, Kc. This we call it as law of mass action, okay? If any coefficient is there, suppose, randomly, if I put any coefficient over here, suppose, if I write here, 2, 3, 4, 5, then we should write here, C to the power 4, D to the power 5, A to the power 2, B to the power 3, right? Like this we write, okay? So this we call it as law of mass action, okay? It says that the equilibrium concentration is equals to the concentration of product divided by the concentration of reactant. And one more thing over here is what, that we know the relation of pressure and concentration, B is equals to CRT. So this concentration term over here, if it is divided by RT, C is equals to, or concentration term, if it is multiplied by RT, you see, it converts into pressure, correct? So when we multiply here by RT, RT, RT and RT, we can multiply it in the numerator and denominator. So this concentration term converts into pressure, right? So when we write down the pressure over here, then the equilibrium constant, there we call it as Kp. It is a partial pressure of product, let me write down like this only, partial pressure of product divided by the partial pressure of reactant, okay? So when you take pressure over here, this term becomes Kp. When you write concentration, this term becomes Kc. One relation we have of Kp and Kc, Kp is equals to Kc RT to the power del N. This del N is what, this del N is the difference of the number of product and reactant, okay? Number of product and reactant, del N with the help of reaction we can easily find out, right? So if this del N is equals to 0, then Kp is equals to Kc, greater than 1, then Kp is greater than Kc, sorry, greater than 0, then it is greater than, let me write down here. If del N is equals to 0, Kp is equals to Kc. We have del N greater than 0, it is Kp greater than Kc, del N less than 0, Kp is less than Kc, right? So these are the three important, from this also they ask question, okay? This relation also, they ask question on to this, okay? Now the next thing here it is what like the, which is important, okay? Some basic thing we have discussed, right? Now see, one thing let me tell you, it's a question, in the question form I'm giving you this thing. Suppose I have one reaction, right? And that reaction is A gives B, right? Its equilibrium constant is given, that is K1, and another reaction we have, we have, that is, suppose C gives D, right? K2. This data is given, the first two reaction, you have to find out the equilibrium constant of this reaction, A plus B gives C plus D. You have to find out K for this reaction in terms of K1 and K2. The first question is this, second question is A plus C gives B plus D, what is the value of K in terms of K1 and K2? Tell me the value, yes, anyone? K1 into K2 for the second part, okay? K1 by K2 and K1 into K2, yeah, it's correct. You see, actually, how do we get this reaction from the given reaction? That's the question first, okay? So first of all, you see, this two reaction we have, if we subtract these two, right? If you subtract these two reaction, we'll get what? A minus C gives minus D, correct? If I add these two, it becomes, okay, let me add this first, A plus D, A plus C gives B plus D. In this, I have made one mistake, this is not possible, actually. I'll check this, I'll tell you this, what is wrong? I should write down D over here, we'll tell you, wait. See, actually, what happens when we add these two? First of all, from this relation, K1 is equals to what we can write? Concentration of B by concentration of A. And from the second reaction, K2 is equals to what? Concentration of D divided by concentration of C, product by reactant. And for this reaction, for this reaction, equilibrium concentration in constant K is equals to what? Concentration of B into concentration of D divided by concentration of, into concentration of C, right? Now you see this, B by A is what? B by A is K1 and D by C is K2. So K is equals to what? K1 into K2. This is the relation we have for K, K1 and K2. So one thing that you have to keep in mind, whenever we add two reactions, right? Whenever we add two reactions, so the equilibrium constant of the individual reaction should be multiplied, right? So K1 into K2 will be the equilibrium constant of this reaction, right? Now here I made one mistake, I should write down D over here and B here. Then it is fine, okay? Then you see A plus D we have to add, right? So A plus D, now when we subtract the first two equation which is given, okay, make the correction over here. It should be A plus D and C plus B. Now when we subtract these two, we get what? A minus C gives B minus D, right? Which further we can write A minus A plus D gives B plus C. Now for this, if I write down the value of K, that will be concentration of B, concentration of C, divided by concentration of A and concentration of D. Again you see B by A is K1, right? B by C is K2, so C by D is what? 1 by K2, so K1 by K2. So when we subtract two reactions, the equilibrium constant of the individual reactions will get divided like this. We will take the ratio of 2, yeah? Now you see one more thing here. See this reaction we are subtracting here, we get this. One more thing we can do if we reverse because we have to find out, we have to write down A plus D, right here. So what we do, we just reverse the second reaction, D gives C if you write. So D gives C if you write, so we already have A gives B, it is K1. And when we reverse the second one, it becomes what? D gives C, right? But when you reverse this, so this should be what? This should be 1 by K2. The equilibrium constant also get reversed. Now when you add these two, you will get the same reaction which is this. And when we add these two, we know from this one that when we add the two reactions, the equilibrium constants get multiplied. So K1 into 1 by K2 is nothing but K1 by K2, right? Now to sum up this discussion, whenever we are adding two or more than two reactions, the equilibrium constant of the final reaction will be the multiple of the equilibrium constant of individual reactions, which we are multiplying, which we are adding, right? Second point is what? When we are subtracting, the equilibrium constant of the final reaction will be the ratio of the equilibrium constant of individual reaction, okay? The reaction which we are subtracting, which is in the minus, for that the equilibrium constant comes into the denominator. Third thing, when we reverse a reaction, the equilibrium constant will also get reversed. So K2 becomes 1 by K2 over here, right? So this is two, three important points we have which helps a lot in solving the question. Now on the basis of this only, one question I'll give you. You see this one, and the question is 2A plus 2B gives D. And one more real equation we have, A plus B gives C. For the first one, equilibrium constant is K1. For this, it is K2. You have to find out the equilibrium constant of the reaction A plus B plus C gives D. This K is equals to what? K1 by K2. How many of you are getting K1 by K2? Pratik is getting K1 by K2, Visist, Rithvik, Kushal. Okay, everyone is getting K1 by K2. Basically, when we subtract these two, 2A minus A becomes A, 2B minus B becomes B, and this side becomes D minus C, and that's C I have written this side, right? So the question or the relation here will be K1 by K2, the simple one. Okay, now you'll see the next thing that we'll discuss is degree of dissociation, which is represented by alpha. So it is what? It is the number of moles, alpha is equals to the number of moles dissociated divided by total number of moles initially taken. Okay, so basically degree of dissociation out of one mole, how many moles has been dissociated? That is what you have to find out. Okay, this I think you should know, you know all these things, right? There are a few formulas for this degree of dissociation we have, right? One formula, when the vapor density is given, right? When the vapor density is given. So when vapor density is given, if vapor density is given, then alpha can be calculated by it is capital D minus small d divided by n minus 1 into small d. Okay, here you have to keep this in mind that this D, capital D is the vapor density when there is no dissociation or this is the actual vapor density when there is no dissociation. This data will be given. Small d is observed vapor density. All these value will be given in the question. All you have to do is what? You have to keep this formula in mind. Okay, observed vapor density. Okay, this n is important. You must keep this in mind. What is n? It is the total number of product. Total number of product. Okay, only product we see nothing to do with reactant over here. Okay, total number of product. So this is one formula. Now vapor density and molar mass also has relation. We know molar mass is equals to what? Molar mass is equals to 2 into vapor density, correct? So this formula, we can also write down in terms of molar mass, right? So the second formula will be alpha is equals to, alpha is equals to molar mass minus small m divided by n minus 1 into small m. Again, small m is what? Observed molar mass and m is what? The molar mass or the given molar mass when there is no dissociation. Okay, just d is equals to or molar mass equals to what? We'll write 2 into vapor density, right? Multiply by 2 here, 2d minus 2d and 2d here also. This 2d becomes m, small m is small. That is what the formula we have. One more formula which is not that much important. Okay, this formula, there are a few questions that you may see, okay? One more formula we have when, excuse me, when temperature and pressure is given, okay? When temperature and pressure is given, right? So alpha is equals to, we write T1P2 minus T2P1 divided by T2P1. This is the formula. This formula is not that much important. Yeah, we have one formula in terms of temperature and pressure that we have to keep in mind. Reaction quotient concept I think you know already, right? So that I am not discussing. If you have doubt, you ask me then I'll discuss. Otherwise, let it be a reaction quotient concept, okay? When Q is equals to Kc, the reaction is at equilibrium. When Q is greater than Kc, then backward reaction favored. Q less than Kc, forward reaction favored. Today also I have discussed this one of the class, right? This in the class, right? One relation we have of equilibrium K is equals to Ae to the power minus del H by RT, right? This only suggests that K depends on equilibrium constant depends upon temperature, right? When we write, when we take log and we derive the relation at two different temperatures, so log of K2 by K1 is equals to minus del H divided by 2.303R1 by T2 minus 1 by T1, okay? Now you see if the reaction is exothermic, del H is less than 0, right? So when del H is less than 0 as T increases, so T2 greater than T1 when T increases, correct? So 1 by T2 less than 1 by T1 and 1 by T2 minus 1 by T1 is less than 0. This term is negative, this negative, this negative becomes positive, del H is already negative, so K2 is less than K1 we are getting here, right? This is only the one I have, I am discussing here, rest you can understand, okay? K2 is less than K1, right? So what we can say in this that in exothermic reaction as temperature increases, equilibrium constant decreases and backward reaction will be favored, right? Whenever K is increasing, the reaction has tendency to go into the forward direction. If K is decreasing, then backward reaction will be favored, right? So what we can say, exothermic reaction as temperature increases, backward reaction will be favored since K is decreasing. Reverse of this, when the K is decreasing, then we will get K2 is greater than K1, so forward reaction will be favored. Similarly, you can understand for endothermic reaction, there will have del H greater than 0. Again, two case you can analyze into this what will be the relation of K1 and K2 that you can understand, okay? Now, we have one more relation of del G and equilibrium constant, right? One relation we have del G that is a change in Gibbs free energy is equals to del G0 plus 2.303 RT log Q, reaction constant, right? At equilibrium, what happens? At equilibrium, this is the Gibbs free energy at standard condition, del G0 it is, at standard condition, right? At equilibrium, this del G is equals to 0, it's not del G0, it's this one. Del G is equals to 0 and Q becomes Kc, when you substitute these two here, so we will get del G0 is equals to minus 2.303 RT log Kc, right? RT log Kc, okay? So, this is again one of the relation we have which is again important on the basis of this also, you will see some questions, okay? Now, the next thing we have here that is leach-athlete principle, we will discuss that with the questions, okay? We'll see few questions which has been asked, okay? But before that, one important discussion we'll do in leach-athlete principle which is related to the physical equilibrium, okay? Physical equilibrium we'll discuss. So, you all must copy and I don't know whether you have done this or not in the last year you have done it or not. I do not know but you do this, right? Okay, this one, right on leach-athlete principle and heading you put physical equilibrium. See, if del H less than 0, see, we are taking a condition. It is not about when exothermic or endothermic reaction is there, so what will be the final temperature? What I am telling you that if the reaction is exothermic then del H will be less than 0. Now, for this reaction which is an exothermic reaction, if we increase the temperature then what happens? And then if you decrease the temperature then what happens, okay? So, final temperature it's fine, like when the heat is going out, obviously the final temperature will decrease but the same reaction which is of exothermic in nature we can have that reaction or we can, like the reaction may be there at different temperature, we can give it higher temperature, we can do that particular reactions at lower temperature. So, what happens when the same reaction is at higher temperature and lower temperature, that is the question, okay? So, the condition we are taking that at this endothermic reaction when temperature increases, what happens? When temperature increases, what happens? So, exothermic, endothermic, we have two different cases, total four cases we have, okay? That is the condition we are taking. Now, you write down application of Leach-Atelier's principle, this is important, okay? So, you just try to understand application of Leach-Atelier's principle. You know what is Leach-Atelier's principle? What is Leach-Atelier's principle, do you know? See, Leach-Atelier's principle is what? When an equilibrium is subjected to any change, right? When you are changing the equilibrium state or if you are disturbing the equilibrium state in any process, equilibrium in any process or reactions, like if you are changing the concentration, if you are changing the temperature or pressure, right? So, any change in all these terms or if you are adding catalyst, right? And all these things depends on the stoichiometry of the reactions also, right? Suppose you have any reactions and suppose if you are changing the concentration of product, if you are changing the concentration of reactant, sorry, concentration of reactant, or if you are changing the pressure or if you are changing the temperature or if you are adding the catalyst, okay? Any change in this kind of will eventually disturb the equilibrium of the reaction. Suppose the catalyst is positive, right? So, that will increase the rate of the reaction. So, equilibrium will attain faster in that case, okay? If you are increasing the concentration of reactant, right? So, again, it tries to maintain the equilibrium. The reaction starts going into the forward direction, right? So, that is what the leachatolias principle we have. Any change in concentration, temperature or pressure, or if you disturb the equilibrium, the reaction goes in that direction which will minimize the change that you have produced in the reaction, okay? So, yeah, it's under physical equilibrium. I'm just giving you a brief idea of leachatolias principle. Then I'll tell you, physical equilibrium, have you done this in the last year, physical equilibrium? Like, what is the effect in boiling point of water when we increase the temperature and all? Have you done this, physical equilibrium? Okay, fine, yeah, yeah, yeah, okay. So, tell me one thing then. Suppose I am taking application of leachatolias principle, I am taking what? I am taking boiling of water, boiling of water. So, H2O liquid, H2O liquid will convert into H2O gas, correct? Now, you tell me one thing, if we increase the pressure, right? If we increase the pressure, then what happened on the boiling point of water? If we increase the pressure, then what happens on the boiling point of water? Will it increase or decrease? If pressure increases, then boiling point increases or decreases? Boiling point increases, okay. So, I think most of you are saying increases, but it is a mixed response. Three, four responses are there, decreases. See, actually, you can understand this by two methods. Since we have done solution also, and I have discussed boiling point, why? If you remember, I have discussed why the boiling point of water is 100 degrees Celsius. Yeah, I have discussed this why the boiling point of water is 100 degrees Celsius, because at 100 degrees Celsius only, the boiling, the vapor pressure of water is equals to the atmospheric pressure. And when we increase the atmospheric pressure, then it requires, water requires more heat to reach that particular pressure of atmosphere so that its vapor pressure increases. And hence, we say that the boiling point of water increases, okay. So, boiling point will obviously increase since we are increasing the pressure. I have taken the example why cooking is difficult at higher altitude, because the pressure is less over there, okay. That is one way through which you can understand. We have one more way to understand, right. The point is what? S2O, liquid to gas conversion is there, right. Liquid to gas conversion is there. Now, when you increase the pressure, right. When you increase the pressure, then to minimize this, because according to Leach-Atelier's principle, whatever change we produce, the reaction will move in such directions so that that particular change is minimized, right. If pressure increases, then how do we minimize this? By decreasing the volume, according to Leach-Atelier's principle, when pressure increases, to minimize this, we have to decrease the volume, means volume decreases, right. It means what? When you increase the pressure, the reaction starts moving into that direction where the volume is less. According to Leach-Atelier's principle, right. Now, you tell me one thing, whether in which direction the volume is less, whether backward direction or forward direction. In which direction the volume is less, backward or forward. In backward direction, the volume is less, right, correct. No, it's not forward, Pratik, because you see in forward direction, we have gas, right. So, gaseous molecule always occupy more volume than liquid and then solid also, right. So, gaseous volume, gaseous molecule occupy more volume. So, obviously, this side, liquid side, we have less volume than the gaseous side, correct. So, here you see, the liquid molecule will have less volume and this side, we have what? Large volume or more volume, right. So, when we increase the pressure, the reaction goes in that direction where the volume is less. So, obviously, under this condition, the reaction starts moving into backward direction, right. Now, you see one thing, like you just listen to me carefully, right, this one. At the same condition, liquid is not converting into gas, but gas is converting into liquid. It means the vaporization or evaporation or boiling of water is difficult over here. If it is easier, then obviously liquid starts converting into gas, but it is not the thing over here. The thing is what? The gas is converting into liquid. It means the boiling is difficult, boiling is difficult. It means what? That the boiling point has been increased and that's why we say as pressure increases, boiling point increases. Is it clear? Is it clear? Tell me. Now, second case we take, that is melting of ice, melting of ice, okay. So, melting of ice means what? H2O, solid is converting into H2O, liquid, okay. In this, you tell me as pressure increases, then what happens? More water will form or more ice will form in which direction the reaction goes as pressure increases. Pressure increases, then what happens? Whether the reaction goes into forward direction or backward direction. Pressure increases, freezing point increases. Yeah, that's correct. Freezing point increases means forward. Yeah, correct. You see, you can understand. This is the special case because usually solid substance has high density than the liquid substance. Solid substance has high density or more density than the liquid substance. But it is a special case of ice because ice is a solid, but it has low density, right. Ice has low density in comparison to liquid. This liquid has high density, okay. Now, if it is low density, it means what? Low density means what? High volume, okay. If density is low, it means the volume is high volume. High density means low volume. I'm explaining you this thing in the same way. Like here, we have compared with volume. You see, less volume, large volume, then pressure increases. The reaction should go in towards the direction where the volume is less. The same thing I'm trying to explain over here. Yeah, volume of ice is greater than volume of water. High volume. Now, you see, again, the pressure we are increasing. So, reaction should go what? In the direction where the volume is low. So, this will go towards what? Forward direction. So, at the same, under this condition, the reaction moves in forward direction. Forward direction, right. Frizing point increases, right. So, in this case, when the pressure is increasing, forward direction, the reaction goes and more water forms. More water forms. This is the special case of ice we have, correct. But you see, if you take any other substance, right, suppose the third one we are taking, melting of other substance, other solid substance, in case of ice, the thing is different because ice has low density than water, right. But if you have any other substance, solid substance, suppose we have XS and if it is going into liquid, that is XL, right. So, in this, what happens, since this XS solid has more density than water, correct, than the liquid, okay. It has high density, high density and this liquid has low density. But in case of ice, this thing was reversed here, right. High density means what? Low volume. Low density means high volume. Now, in this, if we increase the pressure, if we increase the pressure, reaction goes towards low volume as pressure increases, then backward reaction, backward reaction and then freezing point, freezing point decreases, more solid forms. Solid forms, correct. Yeah, that's what, that's what's with, correct. Freezing point decreases. There's a freezing point. No, it's not about water, Shweta. This is for any other substance. Here what we say as the reaction goes towards forward direction, so freezing point will increase over here because the formation of ice is difficult, more water is forming. If the freezing point decreases under the same condition, then more amount of ice should be there. Is it clear? One last application of this. We'll see some questions after this. Fourth one, diamond and graphite. And graphite, okay. See, diamond has high density. Diamond has high density than graphite. The density of diamond is high and this has low density. High density means low volume. Low density means high volume. As pressure increases, as pressure increases, the reaction goes backward and more diamond forms in this case. As pressure increases, yeah, right, Shweta. It should be opposite. So as pressure increases, the same thing, I'm not writing down everything here. More diamond forms. One more information I'm giving you here. This process is an endothermic process. Right? This is an endothermic process. You should keep this in mind. So del S should be greater than zero. Now in endothermic process, as temperature increases, what will be the K value? K will increase or decrease, tell me. As temperature increases, then what happens? K increases, right? So when K increases, then what happens? The reaction goes in forward direction. K will increase. Mine won't. Check your calculation. As endothermic reaction, when temperature increases, log K2 by K1 will be positive in that case. Log K2 by K1 will be positive in that case. Log K2 by K1 is positive. So yeah, so it will increase. So when K increases, as temperature increases, K increases, and when K increases, the reaction starts going in the forward direction. So more graphite will form. More graphite forms, right? If I ask you, as temperature decreases, when temperature decreases, then K also decreases. Then more diamond will form. Accordingly, you have to answer this, right? Yeah. Now you see some questions on this. Okay. The question is, we have to find out total pressure. Okay. Calculate the total pressure. Okay. I'll write down the question. Calculate the total pressure. Calculate Pt. Total pressure developed in a vessel containing a mixture of three parts of H2, three parts of H2, and one part of N2. And one part of N2. To give a mixture, to give a mixture, 10% ammonia containing 10% ammonia at equilibrium. 450 degrees Celsius. This percentage is given on the mole basis, mole percentage. It is. Okay. At this temperature, the Kp is given. It is experimental value, so it should be given. It is 1.6 into 10 to the power minus 4 atm. Try this one. Done. 0.04 atmospheric. Total pressure, Vaishnavi. We have to find out total pressure. It's not right. 1.4. What are you doing? Okay. See. Okay. The reaction is what? It is given that three parts of H2, right? So we'll write N2. Plus 3H2. And this gives 2N is 3. And Kp value is given for this one. Now, you see, since it is given in the question, three parts of it and one part of nitrogen. So we have to take this mole ratio in 1 is to 3 only. That ratio you have to maintain. You cannot assume one mole and one mole over here. Okay. That is one thing. So what I'll do here, I'll just take one mole of this N2 and three mole of H2 here. 1 is to 3 ratio. So I'll take the simplest ratio. But whatever you take, the ratio must be 1 is to 3. 1, 3, and this is 0 initially. Now, we'll write what? 1 minus x. 3 minus 3x. Right? Because one mole reacts with 3. So x reacts with 3x. 3x. And this is 2x. 7.13 is also wrong. Okay. Now you see what is given next. Make sure containing 10% ammonia at equilibrium. Now, suppose we have equilibrium over here. So what is the amount of ammonia present? That will be what? Amount of ammonia is what? 2x divided by, it is the amount of ammonia moles of x, moles of ammonia divided by total number of moles. Total number of moles will be what? This plus this plus this. That will be 3 plus 1, 4. 3 plus 1 minus 4x plus 2x. So I think 4 minus 2x we have total number of moles. 4 minus 2x is the total number of moles. Correct? This into 100 is equals to 10. Is it clear? It is given in the question. The percentage composition of ammonia. Since it is given as mole percent here you see. Mole percentage is given. I have taken mole over here. 0.43. Shweta, that is also wrong. Fine. No, this one is correct. Now from this you can find out x. Right? And when you solve this, you'll get x is equals to. So, okay. So I'll write down, suppose this is 2 and 2 will get cancelled. So x divided by 2 minus x is equals to 0.1. So that will be x is equals to 0.2 minus 0.1 into x. So that will be x is equals to 2 by 11 we are getting. This is the value of x. 2 by 11. Correct. 2 by 11. Now it's simple now. KP you have. So KP you have to find out. Make sure containing this how we have to find out total pressure. So KP is what? It is the partial pressure of NH3. Right? Partial pressure of NH3. Square. Yes. Because 2NH3 we have divided by partial pressure of h2 cube into partial pressure of N2. Partial pressure of NH3 will be what? It is 2x divided by 4 minus 2x into total pressure. I'll write down separately this one. It's better to calculate PNH3 separately and then we'll substitute over there. Okay. So 2x is what? 2x is 4 by 11 divided by 4 minus 4 by 11. So you'll get 11 into 4 is 44 minus 4 is 40. So it is 1 by 10.1. Right? Now. Pressure of N2. Forgot to write here. Total pressure Pt. It was P the total pressure. So 0.1 into P. Pressure of N2 will be what? 1 minus 2 by 11. So 1 minus 2 by 11 is 9 by 11 in the numerator. Divided by again 4 minus 4 by 11. So 40 again. So 9 by 40 into P. You also will write P. Right? This is 1. This is again. And the pressure of H2 will be 3 into 1 minus x. 1 minus x is 9 by 11. So it is 27 by 11 divided by again 40 by 11 into P. That will be 27 by 40 into P. Okay. Then we have to substitute this here. And then you have to solve. Little bit of calculation. I know it is there. This question was asked in Bitsack. Okay. The answer is 30 ATM. Yeah. 30.03 is the correct one. Okay. So total pressure. We are getting here. 30.03 or 30 atmospheric. It's right. So little bit of calculation you have. What else? If this kind of question you have, you got this kind of calculation. You should leave this kind of question for the last. If you have, if in the last you have 10, 15 minutes left, then you can solve this calculation and then you'll get the answer. Okay. So 30 atmospheric is the right answer. Okay. Another question you see. Okay. You see this one. One reaction is given. I will not give you much questions in which the calculations are involved. Okay. Conceptual. I want you to understand the concept. You see this reaction is given. Plus Y. Gas. And this gives. X three. By gas. This is the reaction it is given. The question is. Equilibrium is affected by. Okay. The question says. Equilibrium is affected by first option. We have temperature and pressure. Second one. Only temperature. Only pressure. Temperature. Pressure. And catalyst. Think on it. And then answer. Answer. Why not be. Sanjana. Vrishali. Rithvik. Why not be answered. Changes both equally. Catalyst. The reaction proceeds faster. That's all. Because alter forward and backward reaction equally. It only increases the. Rate of reaction. Correct. Correct. See actually what happens. Catalyst won't affect the. Equilibrium condition. Equilibrium thing will not change by catalyst. It only helps the reaction. To go with a faster rate. If the catalyst is a positive catalyst. Right. If it is a positive catalyst. The equilibrium will attain faster. Right. It won't change the equilibrium condition means what. Suppose you have a reactions. Without any catalyst. Right. So you try to understand like this. Suppose if I. Take one graph here. Okay. Now suppose like I. Have told you the. Graph. Goes like this. Okay. For any reaction it goes like this depending on. The reaction is endothermic or exothermic. Right. If it is exothermic. The product will be. Will have the lower energy than the reactant. This is the energy. And this is the progress of reaction x axis. Of reaction. Okay. Now what happens this is suppose this is the reaction we have. Without catalyst. Without. Catalyst. Now if I use one catalyst into this and if the catalyst is suppose. The positive catalyst if you have. Then that positive catalyst what happens. Will decrease the activation energy. And the reaction proceeds like this. So this is the decrease in activation energy. Initially the activation energy will be here is here somewhere here. Now the activation energy decreases. So you see the final and initial and final position are same. But since this blue one this yellow one is with catalyst. With catalyst. So what it does. It decreases the activation energy. And helps the reaction to attain equilibrium with a faster rate. That is what the purpose of catalyst we have. If it is positive. Suppose the catalyst is negative catalyst. That will increase the activation energy like this. And then the reaction proceeds. But again the final position will be same. Okay. So that won't change the initial and final position. So equilibrium does not affected by. Does not affect by the catalyst. It only changes the rate of forward and backward reaction. Okay. That is only the thing we have. Now as this pressure thing is concerned. I'll just discuss one thing here. And that's why I haven't discussed this thing. Separately in Lee Chatelier's principle. Okay. Effect of pressure if you have to understand. Correct. So how do we. First of all I'll tell you the answer of this. The answer is it's correct. All reactions. Get affected by temperature pressure. Concentration. Of them of reactant and product. Okay. Temperature pressure will always have some effect on the equilibrium. Right. Because. Most of the reactions are what it is exothermic or endothermic. Whatever it is temperature will have one effect. If it is not mentioned that there is no del S will be zero. Then maybe one thing it is there. But since it is not mentioned. So. Temperature will also have. Will definitely have one effect. Okay. Now pressure like how do you assume. Suppose I'll just. Explain you one thing over here that is effect of pressure. Okay. Suppose we have a gas. Plus B gas. I'm taking any general reaction. And that is what we have here. Right. This gives you. See. Gas and D gas. Now in this you see. Since. Dell NG is zero over here. LNG is zero. Right. So KP if I write for this reaction. KP if I write and this is the type of reaction where. Dell NG is equals to zero. Because. Number of product one plus one two minus one plus one two it is zero. Correct. So KP is equals to what the partial pressure of C. Into partial pressure of D. Divided by partial pressure of A. Into partial pressure of B. And that will be mole fraction of C. Into mole fraction of D. Divided by mole fraction of A. Into mole fraction of B. Into P square here also we get P square. Here also we get this P is what it is a total pressure. P is the total pressure. Correct. So this P. Square and P square gets cancelled over here. Right. Is it clear. Basically what happens. If the reaction is of this type. When Dell NG is equals to zero. You see if KP is independent of pressure over here. Right. This KP is independent of pressure over here. When it is independent of pressure. So pressure won't have any effect on equilibrium. Won't have any. Effect at equilibrium. So if the reaction is of this type. Where Dell NG is equals to zero. Suppose the same question if I ask you. For this reaction. Then the answer will be only B. Only T. That is the option. Okay. Since Dell NG is equals to zero. So in the expression of KP. There is no pressure term involved. So pressure won't have any effect in this reaction. And the reaction is only affected by. The temperature answer will be B. For this particular reaction. Understood this. Now if I write down this reaction. Where Dell NG. Greater than zero suppose. And that will be suppose this. A gas. Gives B. Gas and C gas. Suppose this is the reaction we have. Obviously for this reaction. Dell NG. So if it is. It was liquid state. The product. The reactants. Gases state. We won't consider liquid state here. Because for liquid. For liquid molecule and reaction. We don't consider partial pressure. So we'll not get any liquid state over there. If it is there. You just have to ignore them. Okay. You have to ignore them. Now suppose if Dell NG is greater than zero. So I'm just in short. I'm right on the KP expression because I hope you have. You have got it already. So KP expression will be. The mole fraction of B. Into mole fraction of C. Divided by. The mole fraction of A. Into total pressure will be there. Because in the numerator we have P square. And here we have P. Is it clear. This one. The second one. Is it clear. Tell me. Right. So this kind of reaction. Where. Dell NG greater than zero. Or less than zero. Will have some effect on. Equilibrium. Right. So that's why you see the reaction here it is given. It is Dell NG is what in this case. Sorry. Dell NG. Is less than zero. Which is the next case we have that will see just now only. Like I told you in the beginning. That will try to understand the concept with the help of questions that has been asked. And let me tell you one more thing. This question was again asked in J. Okay. So we are only discussing good questions now. Okay. So you see. Now you tell me one thing. Obviously that you have understood this. That pressure will have some effect because KP terms involve KP expression involves pressure terms over here. Correct. Now if I ask you this thing as pressure increases here. Then in which direction the reaction proceeds. Tell me. As pressure increases. In which direction. Reaction proceeds. Forward or backward. Backward backward. So. Backward right. Why it is backward because you see when pressure increases. When pressure increases this KP is independent of pressure. Right. It depends only on temperature. Right. For equilibrium to maintain this KP wants to be constant. Right. The tendency for KP is to be constant. Right. So when this pressure is increasing to maintain this ratio over here. Now XA will also have to increase. Correct. Then whatever amount by this pressure is increasing. If XA will also increase then this ratio will be maintained and KP will not change. The point is what KP tries to maintain this value its value. Right. Since it has it always always have the tendency to maintain the equilibrium. So KP does not have the tendency to change. Right. To get itself change. Right. So when it is increasing the pressure XA has to increase so that this ratio will maintain and when this XA will increase. So what I should write here as P increases according to Lee Chatelier's principle XA should increase when XA increase it is only possible when the reaction goes in backward direction. Backward direction. So as pressure increases backward direction. Right. Backward reaction favorable. Again we can say what as pressure decreases then reverse of this will be true and that will be what forward forward reaction favorable. Right. So one more case the last one I just which is nothing but this Dell NG less than zero for this reaction only suppose if I write down the KP expression that will be what a fraction of this product X3 Y divided by mole fraction of X cube into mole fraction of Y divided by P cube into P P4 and P over here here we have P cube. Right. So basically this expression is not important the only thing you have to keep in mind that the KP expression involves pressure term. So obviously the equilibrium affected by the pressure here. Right. So answer will be temperature and pressure option. Right. So like this you can easily write down the expression of KP and you can understand whether that whether it is independent of pressure or not. One more thing you see this question is also has also been asked in J this one for one reaction and the reaction is this next question I'm giving you. Reaction is A2 plus B2 gives to AB to AB and for this the equilibrium constant is given which is K. Right. What is the equilibrium constant for the reaction AB gives half A2 plus half B2. Tell me the equilibrium constant for the second reaction one by root K. So all of you are getting the same. Yeah, I think it's correct. Okay. So by whatever number we are multiplying that will come onto the power of K. Right. So basically like so when we reverse this for this it becomes K one by K and since we are multiplying this equation by half so one by K to the power half whatever number with which we multiply the reaction that number comes onto the power of it power of it this K why one by K because we are reversed this we have reversed this reaction. Okay. Next question you see same kind of question you see this question was also asked is also asked in J this was also in J. Okay. This is also asked in J and the question is H2 gas plus I to gas gives to H I to H I gas. Then the question is KP changes with KP changes with first option total pressure PT second option catalyst third option amount of H2 and I to H2 and I to and the last one is temperature. It's D. Vaishnavi is saying it's D. This is also asked in J. Yeah everyone is saying so it's correct. You see actually for this reaction you see Dell NG is what? Dell NG is zero. So obviously it is independent of pressure just now we have discussed. Okay. So this is not possible. Catalyst again we have discussed not possible amount of H2 and I to won't KP because accordingly this ratio of product also will change also not possible only temperature it is possible. Right. Simple reaction. It is simple one. It is nice. One question that they have asked in this. Okay. See this one the degree of dissociation question is this the degree of dissociation is point four. I'm giving you in short data only I'm giving you alpha is one point four four hundred Kelvin at four hundred Kelvin and one ATM pressure and one ATM pressure for the gaseous reaction and the reaction is this PCL five converts into PCL three plus CL two. All these are gaseous reaction. All gases behaves ideally calculate the density of equilibrium mixture. You have to find out density of equilibrium mixture at the same temperature and pressure the relative atomic mass of phosphorus is given it is thirty one and for chlorine it is thirty five point five. You have to find out the density of the mixture. The relative atomic mass is given gases are behaving as an ideal gas. Why not see. Okay. See why C is not possible because suppose if you the thing is KP changes with obviously KP will have certain value right at equilibrium because every reactant and product will have certain number of moles at equilibrium and according to that will have the partial pressure. Okay. So when the KP will change when the number of moles of these reactants and product will change. Correct. So what we are doing we are amount of suppose if you take the higher amount of H two and I two according to that only the amount of H I also will also form. Understood. So this KP since temperature we are not changing. So KP value will be maintained accordingly if you take high amount of H two and I two more amount of H two and I two more amount of H I will also form so that the ratio will be maintained ratio of partial pressure will be maintained. Understood. This question is a subjective question. There is no option in it. Okay. The question that I've given you subjective question as in J means 1980s 84 or something 1998 J main 98 10.64 the density of the mixture 10.64 you are getting how it is 10.64. It's wrong. It is not tough check your calculation. 5.97 strong. It's not 5.97 4.53 is right 4.53 is close enough is right. Kushal 4.53 is correct. You see actually this is like you know it looks it looked like a bit weird because chemical equilibrium is a chapter and the question is we have to find out density. Okay. But it is not tough at all because you see density we know density is what mass by volume right and in the question I've told you that the all gases follows ideal behavior right 4.53 is correct for week. Okay. Ideal behavior so density if you have to find out it is what it is mass by volume. How do we find out so mass is the masses given in the question tell me mass is given in the question or not. See PCL 5 molecular mass we can find out that will be what 31 plus 5 into 35.5 and this will come somewhere around it is 177.5 177 plus 31 it is 208.5. This is the mass total mass correct. The reaction is starts from this PCL 5 was total masses to not 8.5 gram and since it is the case of equilibrium so which is the reaction takes place in a closed container like I told you whenever the equilibrium case is there the container must be close right open container equilibrium won't establish right and when the container is closed so the mass will be conserved. Mass will not change total mass will not change it is a different case that some of the PCL 5 has been converted into PCL 3 and CL 2 but total mass at any point of time it will be to not 8.5 gram correct. So mass basically we have right mass is to not 8.5 this is already given in the question only thing is what volume we have to find out. Okay. Now how do we find out volume for that the second data is given in the question which says that the gases behaves ideally right and for that we have to apply PV is equals to nRT right. So you see the pressure is given one atmospheric temperature is given 400 Kelvin r value we have already r value will take 0.0821 right. So volume we can find out from here so volume is equals to what nRT by nRT by P everything is given only n is not given that is number of moles right n is not given now how do we find out n n is what n is the total number of moles we have basically right total number of moles so for that we'll apply the concept of chemical equilibrium for this reaction if I write PCL 5 converts into PCL 3 plus CL 2 if it is 1 initially 0 and 0 right. So it is 1 minus alpha this is alpha this is alpha right PM is equals to DRT no it's not wrong you'll get the same thing Shweta you'll get the same thing that is what I'm doing these what is the PM by RT right PM by RT and that is what I'm doing I am taking volume what is the answer you are getting with this PM is equals to DRT check once now in this you see 1 minus alpha alpha and alpha total number of moles at equilibrium will be 1 plus alpha alpha value is given 1.4 that will be 1.4 so n value will be 1.4 yeah I'll check it wait n value will be 1.4 this n value will substitute here 1.4 R is 0.0821 into 300 so 400 to 400 divided by 1 right this gives you volume this volume you substitute here you'll get the answer okay one thing Shweta you cannot use this formula here because this is applicable when we have only one gas present understood PM is equals to DRT applicable when we have only one gas for mixture of gas we cannot use that understood my point for mixture of gas you have to calculate the number of moles why you are getting different answer there because of number of moles because at equilibrium we have PCN3 also present and CL2 also present which has different different number of moles so PM is equals to DRT everyone concentrate on this PM is equals to DRT if you remember there we have we can use this formula only we have only one gas present if you have mixture of gas we cannot use that because which density we are calculating over here density of the mixture no here we have in this formula it is the density of the gas one gas so answer you will get is 4.5354 understood then 4.5354 will be the answer just you substitute this volume over here you'll get the answer the important thing is what you have to keep this in mind that the molecular formula PCN5 you know already calculate the total mass and that mass will not change since this is a case of equilibrium ok ok next one you see this reaction is given A plus 2B gives C plus some heat releases in this process the question is forward reaction is favored by forward reaction is favored by option A low pressure and high temperature low pressure and low temperature low temperature high pressure low temperature and the last we have high pressure and high temperature after this one more question small one I'm giving you you have to find out the active mass active mass of active mass sorry active mass of 64 gram of hi liter flask option C yeah option C is correct low temperature and high pressure you see the reaction is what the reaction is exothermic because heat is releasing it is releasing so reaction is exothermic del H is what del H is less than 0 ok forward reaction we have to go means K must increase into this according to the question K must increase so log K2 by K1 is equals to minus del H by 2.303 R 1 by T2 minus 1 by T1 so this is negative del H negative negative positive this has to be positive for forward reaction right because K2 must be greater than K1 that is a condition we have to satisfy this must be greater than 0 right so 1 by T2 greater than 1 by T1 so T2 is less than T1 means the temperature should decrease so low temperature favored so either this one or this one ok either this one or this one now high pressure since it is the case of what del NG less than 0 just now I have discussed this is favored by high pressure only so option C is correct into this ok yeah 0.25 is also correct 5 minutes more kushal I will give you break ok 0.25 is also correct active mass is nothing but concentration active mass is nothing but concentration so number of mole per liter one last question then I'll give you a break ok one more question one more question we'll see then we'll take a break ok ok you see this one after this you'll get a break one more question we'll solve the vapor density of a mixture consisting NO2 and N204 we have a mixture of NO2 and N204 for this mixture the vapor density is given and vapor density is equals to 38.3 38.3 at 275 Kelvin 275 Kelvin we have to find out the number of moles of NO2 present in the mixture moles of NO2 is equals to what vapor density is the only thing which is given number of moles of NO2 what is the answer tell me the answer 1 by 2 1 by 2 is not correct ok you see I am doing this first of all you see vapor density is given right and what would be the reaction in this the reaction we can write like this N204 converts into NO2 right and when you balance this reaction we should write here 2.5 is not characteristic ok this is the reaction we have ok so now when it is 1 mole it is 0 so 1 minus alpha gives you 2 alpha and what we have to find out moles of NO2 means we have to find out what is 2 alpha correct so if you know alpha you can find out 2 alpha also so basically we have to find out what is the degree of dissociation right and since vapor density is mentioned in the question so you don't have to do anything but you have to use only this formula D minus D divided by N minus 1 into D what is capital D it is a vapor density before dissociation right what is this given this is nothing but the small D vapor density of the mixture small D is the vapor density of the mixture capital D is the vapor density before dissociation so when there is no dissociation there is only N204 present right ok so it's vapor density you have to find out so that will be what molar mass of this is what 14 into 2 plus 16 into 4 divided by 2 this is nothing but the capital D vapor density before dissociation right why by 2 because we know the molar mass is equals to what 2 into vapor density so vapor density we are calculating so molar mass by 2 16 into 4 is 64 64 plus 28 is 92 by 2 is 46 now you have everything substitute here you will get D D is 46 minus small D is 38.3 divided by N I told you this N is the number of product molecules we don't have to do anything with this right how many product molecules we have 2 N is 2 2 minus 1 into 38.3 so when you solve this you will get 0.7 7 and they had divided by 38.3 so that will be approximately if I take 0.2 38 into 2 is 76 right so 0.2 something you'll get 0.2 approximately I'm taking ok and you have to find out 2 alpha so 2 into 0.2 that will be 0.4 this is what you have done Purvik Prathik this is what you have done if you take 0.25 as alpha here then the answer will be 0.5 if you have done like this it is correct otherwise strong ok so answer will be 0.4 ok correct if you have done the same thing then it's correct so keep the formula in mind whenever vapor density is mentioned in equilibrium question alpha you can calculate with this formula I told you in the beginning also this formula is useful for alpha ok so it's already 7 10 by what time will start ok so we'll take a big of 10 minutes we'll start at 7 20 ok 7 25 will start then ok so don't be late 7 25 will start ok ok so we'll see two more questions on this and then we'll start Ionic equilibrium ok see I am not discussing about these kind of questions which is related to this k p k c relation k p is equals to k c r t to the power del n ok I'm not discussing these questions because they are very basic ok on the basis of reactions del n g you can calculate and you can easily find out whether k p is greater than k c or less than k c or equal to k c this kind of question also they ask ok this this particular formula I'm not discussing now ok you can do this question on your own two more questions we'll discuss and then we'll start Ionic equilibrium ok so the next question you see 250 degree Celsius 250 degree Celsius and one atmospheric pressure and one atmospheric pressure the vapor density of PCL 5 vapor density of PCL 5 is given and that is 57.9 the first thing we have to calculate in this is k p and the second thing is percentess dissociation percentess dissociation dissociation when the pressure is doubled when we increase the pressure then what is the percentess dissociation we have to find out solve this one done ok see I'll just give you some hint over here first of all dissociation of PCL 5 the first step is right down the reaction all our gaseous form so PCL 5 gives what PCL 3 plus CL 2 right nothing is given we assume 1 0 0 if alpha is the degree of dissociation then we have it as 1 minus alpha alpha and alpha 79 percent k p is 137 point what is 79 percent rhythmic or second one second one is 79 percent what about the first one it's huge perfect 137.4 is not correct see you first of all you trying to understand the roadmap of the question what is the question what is the you know data or value we required 133 no it's not correct not correct you see you see here first of all obviously dissociation of PCL 5 we have so PCL 5 dissociates like this now k p is what since k p you have to find out so expression for k p will be what it is the partial pressure of PCL 3 into partial pressure of CL 2 divided by partial pressure of PCL 5 total pressure we know and that is one atmospheric ok so partial pressure of PCL 3 is what mole fraction into total pressure so mole fraction of PCL 3 is what alpha is the number of moles of PCL 3 divided by total number of moles this plus this plus this which is one plus alpha into one total pressure similarly if I write for CL 2 that is also the same thing right because alpha is same over here so I'll just write down the square of it this divided by one minus alpha divided by one plus alpha into one right and when you solve this you will get what alpha square divided by one plus alpha into one minus alpha one minus alpha square ok now the point here is what you have to find out alpha if you know alpha you will you can find out k p and that is what the first question and like I told you in the last question also vapor density is given so you have to use what formula to find out alpha you have to use this one vapor density formula so alpha is equals to d minus d divided by n minus one into d right d is given this is nothing but d small d of the mixture vapor density that is capital d of the PCL 5 is what before dissociation it is for phosphorus 31 5 into 35.5 divided by 2 that gives you that gives you 208 this is 50 30 okay so we will get 104.5 by 208.1 gives you 108 104.5 or 25 probably we will get here 25 okay now you see everything is given this is substitute here 104.25 minus 57.9 divided by 2 minus 1 and values 2 because the number of product we have to check PCL 3 and CL 2 into 57.9 and when you solve this you will get 0.80 80 percent alpha degree of dissociation 2 by 3 so 2 by 3 alpha is 0.8 mine 1 correct 1.77 Kp 1.77 Kp is correct Mrs. Drog got the answer 1.77 is correct okay so alpha you have just you substitute alpha here you'll get the answer 0.8 square divided by 1 minus 0.8 square and the answer you will get 1.78 or 77 approximately Kp the first portion we have done now percentage dissociation when the pressure is double excuse me so basically here when the pressure is doubled so this P becomes what 2 atmospheric just we have to substitute here so here we have 2 and 2 Kp will be same Kp will not change so expression I'll write down here 1.78 for the second portion 1.78 is Kp is equals to alpha square alpha by 1 plus alpha into 2 whole square divided by 1 minus alpha divided by 1 plus alpha into 2 this is the expression we have okay and which we get on solving is 1.78 divided by alpha square divided by 1 minus alpha square into 2 okay and when you solve this alpha value you'll get 68.6 percent 0.688 this is the value of alpha you can easily cross check this you see initially at 1 atmospheric pressure alpha is 0.80 which is 80 percent when you increase the pressure alpha decreases that is what possible because for this reaction del Ng is what del Ng is greater than 0 right and that particular discussion that we have already done in this type of reaction as pressure increases backward reaction favorable backward reaction means what the alpha value decreases more reactant will get and that is what we are getting here 80 percent here and here it is 68.6 percent is it clear I see one last question for this chemical equilibrium chapter okay the question is a solid a solid converts into B gas plus C sorry we have D plus D gas B and D Kp1 for this reaction is given which is thousand another one C solid dissociates into Kp2 plus E gas Kp2 is equals to 500 calculate the total pressure this is actually simultaneous reaction okay two different reactant you see two different reactant giving one common product okay so both reaction will obtain equilibrium and the formation of B from this reaction will also affect the equilibrium of this the second reaction because B is same in both reaction try to solve this to make this as 600 your calculation will be easier than this Kp2 you take as 600 not 500 anyone what happened okay you see I am solving this see first of all like I said this is we call it as simultaneous equilibrium okay in which alpha is not given alpha is not required alpha is not required you see I am solving this first of all this is simultaneous equilibrium like I said two different reactant giving a common product at least B is common in this too and it's not like the two reaction is taking place in two different container we have the same container in which the reaction is taking place close container obviously A is also dissociating and B is also dissociating over here since one of the product is common in these two so formation of B here in this reaction that also affect the equilibrium of this and vice versa means both reaction since one product is common over here both reaction will affect the equilibrium of each other right if one particular reaction you remove then we'll have some equilibrium concentration which is different than the now the concentration that we have one atmospheric is not true okay okay now you listen to me carefully right so the point is what since it is solid so this will not have any partial pressure so let's let it be this one now suppose when this reaction takes place so obviously it dissociates into B and D so this B will have certain number of moles which is true for D also and according to that mole will have some certain partial pressure of B and that of D also no it's not true for it okay so suppose the partial pressure of B is P1 and since 111 mole we have so D also it is P1 now here I assume the partial pressure of B in the second reaction is suppose P2 here I'm assuming this as P2 111 mole we have so this is also P2 okay but you see the reaction is taking place in the same container like I said that both reaction affects the equilibrium of each other so B in the reaction vessel whether it is coming from this reaction or this reaction both are both depends on each other so total pressure of B will be P1 plus P2 P1 plus P2 means the total pressure of B if I ask you the answer will be P1 plus P2 the amount of B that is forming from first reaction and the amount of B that is forming from second reaction both will exerts its own pressure so total pressure of B will be P1 plus P2 right now it is easy now you see if I write down the expression for K P1 what is the expression for K P1 partial pressure of the product which is P1 into P1 plus P2 and that is equals to 1000 given in the question again K P2 is equals to P1 sorry P2 into P1 plus P2 and that will be equals to 600 clear is it clear yeah it is clear now any doubt see Vishak the pressure of B will be P1 plus P2 because P2 pressure is because of this reaction and P1 is because of this reaction so total pressure of B is what if I ask you in this vessel where these two reaction is taking place what is the pressure of B how do you differentiate that B is coming from this reaction or this reaction B is B only what is the source of the reaction that is not the concern the concern is the pressure of B in the reaction vessel so P2 is the pressure developing from this reaction P1 from this so total pressure is P1 plus P2 and there only the reaction will attain equilibrium correct so now we have two reactions two equation we have correct what is the question calculate total pressure at equilibrium so at equilibrium what all things we have since total pressure we have to find out so this solid thing we don't consider correct and at equilibrium we have B, D and E correct so at equilibrium we have only B, D and E A and C will not consider since these are solids so total pressure at equilibrium Pt will be the pressure because of B that is P1 plus P2 the pressure because of C that is pressure because of D that is P1 and the pressure because of E that is P2 so the total pressure at equilibrium will be 2 into P1 plus P2 so this is what we have to find out this is what the question is understood now for this you see we have two reactions we have already written you have to solve these two reactions you will get the answer how do we solve this suppose this is reaction 1 this is reaction 2 if you add these two you can take the ratio of these two also but that will be again a bit difficult to solve if you take the ratio of these two you will get P1 by P2 right nothing is given P1 and P2 is not given into this so what will you do I will just add these two so when I add these two left hand side P1 plus P2 I will take common right P1 plus P2 I will take common and in the bracket again we have P1 plus P2 and this will be equals to what on the right hand side 1 6 double 0 so we will have P1 plus P2 whole square so that will be equals to 40 so 2 into P1 plus P2 will be what 80 atmospheric that is the total pressure at equilibrium how do you calculate P1 and P2 a dry line error you can use P1 P2 how do you calculate this sweater P125 P250 the equation you will get P1 by P2 is equals to 10 by 6 okay and then you calculate P1 plus P2 and then you substitute P1 plus P2 into this correct that also you can do that is also you can do if you divide you will get P1 by P2 is equals to 5 by 3 add one both side you will get P1 plus P2 divided by P2 is equals to 8 by 3 P1 plus P2 is equals to 8 by 3 into P2 substitute here you will get so P2 square into 8 by 3 is equals to 600 so when you solve this you will get the answer I think yeah correct you can solve that is not a big deal you can solve and then you have to find out P1 plus P2 and then this but this is the I think easier method anything if you get in your mind you can solve this so understood this this is the question of sequential equilibrium we call it as two different reactants gives you the same one of the same product okay like this will write down the expression of Kp1 is it clear all of you now you see we will start this the discussion of Ionic equilibrium we don't have time actually right but okay we will see just Ionic equilibrium we will continue with this in the next class also let's see what all things we can cover today okay see Ionic equilibrium basically it is a big chapter first of all right and it contains calculation of pH is important and there are 8 to 10 different cases right and in that you have to understand like you know what formula you have to apply yeah yeah yeah I am continuing with it yeah I am continuing with it okay so Ionic equilibrium pH calculation is one of the portion we have right first 50% of the portion contains pH calculation only okay and then we have one concept of buffer solution buffer solution and then we have some solubility product question solubility product okay so these are the basic thing we have in this chapter so first of all we have to understand that what is this Ionic equilibrium see chemical equilibrium we have discussed and we are discussing about molecules over there when I write N2 plus 3H2 gives 2NH3 right so these are molecules we don't have ions present into it you want to solve one more question or should I continue with it okay okay fine I'll give you one tell me quickly one one like numerical you want to solve for equilibrium only or should I start with Ionic okay fine we'll do one question only on this see like I said Kp is equals to KCRT to the power del N those are problems you just go through on your own one question I'll give you okay see this one one reaction is given okay a reaction is this only PCL5 PCL3 and CL2 same reaction I am taking as okay attends equilibrium if the equilibrium concentration of PCL3 is doubled if the equilibrium concentration of PCL3 is doubled the concentration of CL2 becomes the concentration of CL2 becomes first option one four one one fourth one fourth of the original value half of the original value twice of the original value and the last one we have unpredictable what is the answer it's okay we'll start next class question of E one by four half all of you are saying AB AB AB actually the answer for this question is D unpredictable we cannot predict it the only thing we can understand or we can say that when you add product into it the concentration of product you are increasing correct when you are adding PCL3 the concentration of product you are increasing right when the concentration of product you are increasing so obviously the reaction starts going in the backward direction starts going in the backward direction that is the only thing we can say what effect takes place on the concentration of CL2 that we cannot say into this it may be anything right because when this will go this side so for our reaction will also be there what is the effect on the concentration of CL2 that we cannot say the only thing that we can say according to Lee Chatelier's principle that the reaction will go in the backward direction the answer will be unpredictable yes we can say that the concentration of CL2 will decrease because the reaction is going in the backward direction whether it is half or one by four that we cannot say it can be any value understood this we cannot say signing it like that because when the reaction starts going in the backward direction at the same time forward direction is also there the reaction is going in both direction the only thing when you increases the concentration of PCL3 the backward reaction is dominating right so what effect on CL2 takes place that is unpredictable into this K will remain constant obviously because we are not changing the temperature we cannot change to maintain K only the reaction starts going in the backward direction so this is it no the questions we have probably discussed all possible type of questions the only questions that I haven't discussed which is Kp is equals to Kcrt to go to del n and the question related to del g right del g that is only formula based question you have to put the value of RT and Kc over there then you find out del g from there those kind of questions you can go through on your own right but now since we have almost revised every possible thing in this chapter you can solve the questions which is given in the model or any other book if you have correct so next class in the revision class we will start iNIC equilibrium we will see again little bit of theory not in so detail and then we will solve the questions right ok so thanks a lot we will continue with iNIC equilibrium in the next class ok