 Yes, got it. I didn't get your point. No dissociation before vapor density below. Yes. See what happens? I'll tell you how we get this formula. We have a derivation for this, but that derivation is not required. See what happens actually when you have a molecule, suppose a molecule you have, right? So it has certain vapor density, right? D. Okay. When the reaction starts and it converts into different molecules, say B and C. Then in the mixture, we have A, B and C present at equilibrium, right? All three are present. This B and C won't let that vapor density to be as D only. This D only. But this mixture has a different density. Vapor density that is a small D, right? Based on this only this formula is given that when there is a dissociation, so initial vapor density minus the density that we have observed one divided by N minus one into D, where N is the number of product here, because this also has a role over here. Based on that, we have that formula, right? So derivation is not there. Like if you want, we can discuss it but not required. But this formula is useful. Directly, you don't have to get confused over here. Data will be given. If vapor density and density is not given, you cannot find out vapor density on your own. So it will be given in the question. So once the vapor density is given, you can think of this formula in order to find out the alpha degree of dissociation, correct? No doubt. Yeah, tell me. Understood? So basically when molecule dissociates, its vapor density changes. And with respect to vapor density, what change we have in that, we can find out to what extent the dissociation is taking place or takes place, right? With that reference only we have that formula. Tell me. Yeah. Now we'll see some questions on this. See here, 11, 12 and 13 you try. Done? All three questions are you done? Yeah. So 11th one, you see the reaction is given. Carbon solid plus CO2 gas gives two CO gas. Partial pressure of CO2 is given. That is two. And that of CO is four. We need to find out the Kp of the reaction. So what is Kp? Partial pressure of the gaseous product by partial pressure of the gaseous reactant. So four into four divided by two, eight, okay? Now suppose if this, you know, if this value, partial pressure is not given. Suppose in the question, the partial pressure is not given. Could you find out Kp in that case also? See, if partial pressure is not given, then it will be difficult to find out Kp over here. If total pressure is given, then we can find out. Suppose partial pressure is not there, total pressure is there, then we can find out. One more thing you must keep this in mind. Yeah. You see the molar ratio of CO2 and CO is one is to two. That one is to two is given. So partial pressure of CO2 or CO, if I write down, it will be the twice of the partial pressure of CO2. That is for sure because the molar ratio is one is to two. And we know pressure is directly proportional to number of months. So with molar ratio, we can have the relation of partial pressure. Then if total pressure is given, we can find out the partial pressure of each component and then Kp. That is also one way. Okay. Next question. What is the answer? Next one. Number 12. 250 degree Celsius, the vapor density of PCL 5 is 100. Okay. So PCL 5 dissociates as PCL 3 gas and CL 2 gas. PCL 5 gas. At 250 degree Celsius, the vapor density is given. Means vapor density of the mixture we have. So it's small d is given. That is 100. The capital D would be two times of the molar mass of PCL 5. I'm sorry. Capital D would be half of the molar mass of PCL 5. That's the formula we discussed in more concept chapter. If you remember. Molecular mass equals to two times vapor density. What is the molecular formula of PCL 5? Is it 208.5? Is it? Could you tell me this value? So this would be 104.25. Right. Now we have the formula. We use that formula alpha because degree of this is alpha. You need to find out. So it is 104.25 minus 100 divided by N value is 2. 2 minus 1 into 100. One more thing. If you get confused over here, which one is a small d? Which one is capital D? One more thing. You must keep this in mind. This alpha will never be negative. So accordingly you can subtract. Alpha will never be negative. So accordingly you can subtract. So answer would be 4.25 divided by 100. So alpha is 0.04 approximately option B is correct. 13th one. What is the answer? 13th one. Anyone? Okay. Let's discuss the 13th one. 6 gram of hydrogen reacts with this chlorine molecule. So reaction is what? H2 plus Cl2 gives 2 HCl. 6 gram of hydrogen means we have three more. This much atom of chlorine 9.023 into 10 to the power 23. Divided by approximately 6, I'll assume 10 to the power 23. So roughly I'm assuming this as 9 by 6 mole of chlorine. Can we say that? Given number of molecules divided by avocado number. So we have 9 by 6 moles of chlorine. Right. If total pressure of the reaction is this, then what will be the partial pressure of HCl? Okay. The partial pressure is given. That is 800 mm. We need to find out the partial pressure of HCl. So what is the pressure of HCl? It is mole fraction of HCl into total pressure, which is given 800 over here. So if you find out mole fraction, you can find out this, you know, the total pressure over here, right? So you see here, 3 moles and 9 by 6 mole we have. Which one will get consumed completely? Is it Cl2? If Cl2 will get consumed, so number of moles of HCl would be what? 1 gives 2. So this gives 3 moles, right? 3 moles of HCl we are getting. Total number of moles. What is the total number of moles? Nt is equals to the number of moles of H2 plus number of moles of HCl, because there is no Cl2 present here. So if you see, this is nothing but 1.5 moles we have. Okay. So 1 moles reacts with 1. So 1.5 moles reacts with 1.5 moles of H2. So number of moles of H2 left here is 1.5 moles of H2. Total number of moles would be 3 plus 1.5. That is 4.5 moles of H2. We have total number of moles. This X is equals to the number of moles of HCl3 divided by 4.5 into 800. I think the total pressure is given, is it? Yeah, 800 is given. So it is 15 and this, I think we're getting 1.5 and then 8000 divided by 15. And that would be 500 something. It is 533 mm approximately I'm getting. Isn't it? Looking at the options, by looking at the options. 533. Is it fine? Clear? And now guys, this one you try. Question number, 24. 24th one, what is the answer? 24th is, I'm getting all three different answers. Okay, B, D and C, is it? One second, I'll do this 24th one. You see, in this 24th one, we have C plus CO2 gives CO, the equilibrium pressure is 12 atmospheric, 50% of CO2 reacts. Calculate the Kp for the reaction, okay. 50% of CO2 reacts. Okay. So what we need to do here, suppose we have carbon solid plus CO2 gas gives two CO gas. If it is P initially, this would be zero. Half of this reacts, the left, it is left, P by two is left and two into P that forms, right? Because one gives two. So if it is P minus 0.5 P, then this would be P, right? This is given P by two plus P is equals to 12 ATM, right? So 1.5 P is equals to this P is equals to 12 by 1.5. That is the pressure we have. Kp is equals to pressure of CO2 by pressure of CO2. Pressure of CO is P that is 12 by 1.5 square. CO2 is P by two, which is one by two into 12 by 1.5. 16 atmospheric I'm getting. Just you need to solve this. Since the initial pressure is not given, I assume it as P because this is solid, you can ignore this, this is zero. You can also take this as one. That is also five, one concentration. But I assume P and that P we can find out with equilibrium concentration. Yeah, 240 by 1.5 we have over here. It is 240 by 1.5. Once you solve, you'll get this only. This entire thing will get cancelled. This two will get multiplied by this by 1.5. So 240 by 1.5. Is that clear? Okay, next question number 25. Question number 25. Is it A? It is alpha D glucose converts into beta D glucose. Okay. Don't think about this term. Muta rotation. We'll discuss this in 12th grade. It is there in the biomolecule chapter. We'll discuss it over there. Just you understand here, we have some process which convert this alpha into beta. Okay, we also discuss all these things in detail. What is alpha D glucose? What is beta D glucose? Here you just assume these are the two compounds which are inter convertible. So at some condition, 63.6% of glucose is in beta form. Means this is 63.6. And rest is this, which is 36.4, I guess. Right? We have this mixture. Means when you take glucose, right? When you take glucose in the solution, it will have two forms actually. One is alpha, one is beta. That is what you can understand. Beta form is more stable. Its composition is more. And rest is this alpha form competition is less simple. Kc is equals to what? Beta by alpha. 63.6 divided by 36.4. So 36 into two is 72. So answer is less than two here. So obviously B and C is not possible. I think it is 1.7. Is it A? A or D? What are you getting? 26th one. Tell me. Yes. 26th. Are you getting C? Okay. 26th one. You see here. For the reaction, the rate constant for forward reaction, reverse reaction is again very simple. Rate constant is given. Nothing you need to do. Equilibrium constant equals to what? Rate constant of forward by rate constant of backward. This we can do. Rate constant for forward reaction is one into 10 to the power minus four given. Divide by 2.5 into 10 to the power minus two. Right. So it is minus two. Then it is minus one. Then we have four into 10 to the power minus three will get over here. Option C is correct. Okay. This is the answer. So you'll get this kind of questions here in this chapter. Okay. Let's discuss some more concepts here. I guess you don't have any doubt in these kinds of questions. There is. An equilibrium called simultaneous equilibrium. An equilibrium called simultaneous equilibrium. Simultaneous equilibrium. Is the equilibrium. Like in which two different reactions have one common product. Okay. So for example, you see if you have a gifts. B and C. And we have another reactant molecule D. Which also forms B in the same vessel. Are you getting at the condition? Suppose this two reaction is taking place in the same container. What do you do? You take a reaction vessel. Right. A reaction vessel. That's a condition. And in this you place A and D. Simply keep it there. Then obviously what happens slowly. This A starts converting into. Into B and C. And D starts converting into. B and E. This is the reaction taking place here. In this container. Now since the two reaction. Has one common product. Okay. So in the vessel. Wherever we have like if these present. It will affect the. Equilibrium of both reactions. Because both involves B. Right. So whether the B is coming from a. Or D. It doesn't matter. It will affect the equilibrium. Of both reactions. Can we say that. Yes. Agreed. Are you tired guys today? You're not responding. Okay. Are you tired guys today? Yeah. One respond your doubt. Then yes. Can you. Can you hear me? Are you sleeping or what? Okay. I don't see any response from your side. Only few of you are responding. But others are quite. Completely quite I guess. I don't know what happened today. Are you tired today all of you? No. Not that you want to eat something. Pizza. Pizza? with extra C's? Yes, now it's not fine. Whenever we start offline, I'll treat you with pizza. Outside food is not allowed. That's good Shraddha. Let's see, whenever we meet. This is due, but you have to be active in the class for this. Any exam you have in the school, any scheduled exam in the coming weeks. Thursday you have physics, right? When is chemistry? This is what the pre-book of what? As a unit test. Unit test is fine. I can understand. Chem is in January. This is the unit test in January. Okay, fine. I got it. So we'll get back to this. Okay, so what I said, I said that two different reactions gives one common product. That is B here. So what happens if suppose this A and D you have taken in a vessel like this? Okay, so A starts converting into B and C. And at the same time, D also starts converting into B and C. So since we have one common product here in this two reaction, so the presence of B affects the equilibrium of this and this both. It is C. This D won't say like, okay, this B is not, I did not give this B. So this won't affect this equilibrium state over here. In the reaction vessel, wherever the B, the product B is coming from, whether it is coming from A or coming from D, it will affect the equilibrium state of both reactions. Yes, this kind of reaction, we call it a simultaneous equilibrium where two different reactions gives the same product. At least one product is same. Is it clear? Understood? So total concentration of B, if I ask you in this particular vessel, then it would be what? It would be because of A and because of D, whatever we get. Suppose X we get from A, Y we get from B. So total concentration of B or total moles of B would be X plus Y. Okay, so let's write down this. Suppose we have initial concentration of A, I am assuming, is small A here and this one is small B. So initially there is no B, there is no C. When this starts converting into B and C, we'll write A minus X, we'll get X of B and X of C moles. All these are dynamic equilibrium. There's no static. Reaction, whenever you are talking about all chemical reactions, if equilibrium is taking place, then it is dynamic because reaction never stops at equilibrium state. For B, I am assuming it is zero and zero again and we can take because A and D are two different molecules. So we can assume it is B minus Y, different degree of dissociation. It is Y and it is Y. But in the vessel, the total concentration of B is what? The total concentration of B would be X plus Y. Here also we can write down X plus Y and X plus Y because both affects the equilibrium of two reactions. Clear, understood? So when two reaction gives one, at least one common product, the reaction is said to be in simultaneous equilibrium. Both affects the equilibrium of each other. Okay, this is what the definition we have now you see. For this, I am saying it is Kp1. So I am gas, I am assuming this. Okay. This is solid. This is solid. This is gas. This is gas. Okay. Or I'll write down the general expression and I'll tell you what happens here. Let me write down the general expression only. If gas will take, then we'll take the pressure. That's simple. Kc1 and Kc2. So what is Kc1 here? Kc1 equals to the concentration of C into concentration of B by concentration of A. And that would be X into X plus Y divided by A minus X. This is what we can write. Similarly, Kc2 would be Y into X plus Y divided by B minus X. This is what the expression we need to write in case of simultaneous equilibrium. B minus Y. Yes, obviously. B minus Y. Copy? Yep. Now, you see this question based on this. We have two reaction. A solid converts into B gas plus C gas. It is Kp1 here. Value is given 1000. Then we have the next another reactant molecule that is C solid gives B gas, not C, B gas plus we have E gas here. Kp2 is given. That is 600. Okay. Calculate the total pressure at equilibrium. Remember, total pressure is always because of the gaseous product or reactant. So find out what all gaseous product or reactant we have at equilibrium and what is their pressure. Add all those. You will get the answer. Okay. See how do we do this? Since A and D are solid, so you have to ignore this. There is no point of considering solid here. So we have to ignore this. Now, suppose if this A dissociates, it gives some amount of B and that will exert P1 pressure. P1 pressure because we have same is sociometric coefficient. So whatever the amount it forms corresponding to that value, P1 is the pressure we have. Similarly for D, it is P2 and P2, the pressure. Total pressure of B would be P1 plus P2 because it is simultaneous equilibrium. Solid, the concentration and pressure will take as one unity. We don't consider that into the equilibrium expression because these are incompressible. Hence, the concentration or pressure of solid or liquid, you can assume as unity one. Okay. So the expression of Kp1 would be P1 into P1 plus P2, isn't it? Is equals to 1000 because there is no, there's solid present here. So denominator is one, A solid is one. So that's we are ignoring. Kp2 would be P2 into P1 plus P2 is equals to 600 given. Right? What we need to find out, could you tell me? What we need to find out? We need to find out Pt, total pressure. Right? This pressure is because of all the gaseous species, that is the pressure of B, pressure of C and pressure of E. These are the three species we have at equilibrium. So pressure of B is what? P1 plus P2 and pressure of C and PE is again P1 plus P2 we have. So obviously we need to find our total pressure, two times of P1 and P2. This is what we need to find out. So if you have this equation, you can solve and you can find out P1 plus P2 and then two times of P1 plus P2 is your answer. Could you tell me the answer now? Are you getting 80? Okay. So how do we solve this? We'll just add the two. Okay. There are many different ways, but the best way is what? You add the two equation, these two. So left hand side you see you'll get P1 plus P2 common. So overall you'll get P1 plus P2 whole square is equals to 1600. So with this directly you got P1 plus P2 is equals to 40. So what is total pressure Pt? Two times of P1 plus P2, which is nothing but 80. So you see here this is it for this. We are left with two more things in this chapter. The last point that we are going to discuss in this chapter, the last concept, is the most important one that is Lee Chatelier's principle. Okay. Before that we need to discuss Arrhenius equation. So Arrhenius equation will start after the break and then we'll go into Lee Chatelier's principle. Okay. The last topic of this chapter. So we'll resume the class after the break at 6.30. Okay. Take a break now.