 Yes sir, you can do it for any order reaction, but the thing is again that since in this question is clearly given first order you have to find out correct that you need to prove, but suppose if they ask you the order of the reaction, then you have to assume one by one. Okay, zero order first order and then second order that you can do. Obviously if you assume zero order, then you have to take the expression of K for zero order reaction. Are you getting it? Yes. But the value of K for two set of data will be equal only when your assumption is correct. Yes. So, mostly for zero and one you will get the answer and second thing or suppose if you get this question in the exam they are asking you the order of the reaction in comparative exam, then we know in zero order equal amount will react correct. In equal time interval, 240 second, suppose if equal time interval is given, then equal amount must react. If that is not there, it means zero order is not possible. I'm not talking about this question in general I'm talking about. So, suppose zero to 220, 220 to 240, then again to 480. If it is 480 here, then this the amount that reacts over here equal amount should react here in equal time interval. If it is zero order, yes. Yes, yes. If it is first order then what we'll do? Percentage that reacts must be same. So, we'll find out the percentage which reacts over here. So, in that way also you can do obviously this kind of question if they ask them competitive exam, they want you to you know waste your time because it will just a hunch you're using over here. Okay, zero order and then this kind of question I would say, if it is very calculated you're not getting it quickly, then leave it for the last like if you have lasting 15 minutes left and you can try this kind of question, don't waste time on this. So, we'll move on. So, next, you know, see all these things if you recall the last class, we were talking about the factors affecting rate of reaction. Yes or no. We have discussed the nature of reactant and product, we have discussed concentration and all these things, order and everything that we have discussed, RLE and all, it is under the concentration factor, correct. So, let's go back and just revise quickly that we were talking about the factors affecting rate of reaction. And in the concentration factor we have discussed this much of thing, which is mostly in a half of your chapter. Correct. Now the next factor is that is temperature and the next one is catalyst. These two factors we need to discuss, but before going into temperature, we'll discuss one small concept that is molecularity. Theoretical thing, we'll finish this and then we'll move on to the temperature, the other factor here. So, heading you right down, molecularity. In board exam and in comparative exam, they ask questions about this, with this molecularity and order. In board they, many times they have asked this, write down the difference between order and molecularity. Okay, very common thing, it's given an NCRT also. Okay, write down molecularity. It is equals to, it is equal to, let's call that the way, equal to the number of molecules, reactant molecules, write down, number of reactant molecules involved in, involved in, dimension you can use Venkat, if K value is given, no, K-car unit is not given over there, correct. Oh, what I thought sir, we could take one, we could find out K respectively and then do it, but then since we're equating K, I, okay. We're just taking different values and finding out cases that are equal, okay sir, got it. Different orders actually, that you can do if K value is given with unit, then you can understand, okay, this is the order of the reaction. But here the K value is not given, you don't know what value of K you're going to get. Plus the unit also. If unit is given, you can do that. Number of reactant molecules involved in, involved in the balanced reaction, involved in the balanced reaction. Point was write down, it is the theoretical concept, theoretical concept. And if in complex reaction, in complex reaction, we check the number of molecules, reactant molecules. When I say molecules here, reactant molecules present in, present in the slowest step, slowest step. So we just have to see one single step, right. So if you have complex reaction, so molecularity we define with respect to the slowest step, if multiple steps are there. So hence we also say it is defined for elementary reaction, means one single step, elementary reaction, that also we see, okay. It must be a whole number because it is a sum of the molecules, so it cannot be zero negative or fraction, correct. So it must be a whole number, or must be a integer, not whole, must be zero is not possible so we can have one, two, three here. But order if you see order can be anything, it can be zero, it can be negative, it can be positive, it can be fraction, but it is always either one, two, three and like that. Reaction with molecularity, greater equal to four. Some book it is written three also over here, both are rare only, three and four molecularities are rare, three to some extent fine, but four is also very rare. Reaction with molecularity greater equal to four is very rare. It is independent of pressure and temperature, pressure and temperature. So these are the few things, few points for molecularity that you must memorize, difference between order and like it is independent of pressure and temperature. Order depends upon pressure and temperature, that's also we have one point done. Okay. Next the next factor which affects the rate of the reaction we have, write down factor number four is temperature. See temperature has a significant effect on the rate of a reaction, because if you increase the temperature, then the molecules energy, right. Overall average energy if you see for the molecules that also increase, hence kinetic energy increase, kinetic energy increase so we can have more collision, which we can say that collision frequency increases. When collision frequency increases, then rate of the reaction also increases. So write down this, write down temperature has a great influence on the reaction rate, temperature has a great influence on the reaction rate, the reaction rate. In general, temperature increases, in general, as temperature increases, rate of the reaction also increases. Next line, it has been observed that, it has been observed that for every 10 degree rise in temperature, for every 10 degree rise in temperature, the rate constant, the rate constant becomes doubled. Rate constant I'm talking about you see, it's not rate of the reaction. Okay, however, both are related in a similar way, means if rate constant increases rate of the reaction also increases. But it is rate constant which gets doubled. No, here it is not. We'll talk about endo and exo, temperature won't affect the rate. In general, whatever the nature of the reaction, endo or exo, with increasing temperature, the rate always increases. But isn't it a bit contradictory? Why? For exothermic reaction, if you want to produce, if you give more energy, won't it like reduce the rate of reaction is something. No, it's not. Because we are talking about, first of all, you are confused with equilibrium constant rate constant. You are actually you are talking about a reversible reaction. Okay, and I am talking about we have A and B and conversion of A and B into product. So when you increase temperature, the collagen frequency of A and B increases, there will be more collagen per unit time. And hence, the conversion of into product will be more lateral reaction. I'll come to your point. I understood what you are thinking. I'll come to that point. Give me some time. So, this is the thing, right? So, temperature is, in general, what you have to keep in mind temperature increases rate of the reaction increases, why it happens because rate constant increases, k increases. Okay. And the relation of rate, one more thing I forgot. Okay, I said, for every 10 degree rise in temperature, the rate constant becomes double, right? So if you see, if you take the ratio of rate constant k, at a temperature t plus 10 divided by k at temperature t, so obviously we have 10 degree rise in temperature here. This ratio, we call it as mu. And this mu is temperature coefficient, important temperature coefficient. Okay. And this is observed to be nearly equals to two. In the book, they have written, becomes double or triple. This also, they have written in the book. But for solving question, you take this to only. Okay. The temperature coefficient for every 10 degree rise becomes double. Take care. Is this fine? Sir, how is it the same for every reaction? Same as in what? It doubles for every reaction if you change the temperature at 10 degrees. It depends. That's what I said. It has been observed. It's an experimental thing because it depends upon the collision frequency, plus the energy barrier. Okay. So whatever the nature of the, obviously it is not true for all the reaction. It is there for some of the reaction. For few reactions, it becomes tripled also. So if it is two or three possible, it is also possible that could be any other number. But mostly, it becomes almost double. Not exactly equals to almost double. That is the experimental observation we have. For our sleepers, for our question that you get related to this, you have to take the ratio as two only. You won't get any other value over here. Or you can say in other way, that the reaction that they give here in this chapter in our sleepers, for those reactions, the ratio for every 10 degree rise is coming out to be two. Both of you can understand. Why it becomes double or triple, that there are two to three factors, collision frequency, plus energy barrier also we have over there, which can overcome easily. Okay. We'll talk about that energy barrier after some time. Okay. So this is what we observed overall. We discussed overall that what happens overall if you increase the temperature. Correct. But the relation of rate constant with temperature is given by a scientist called Swedish scientist called Arrhenius. Okay, it is observed by Dutch chemist called went off that okay rising temperature, temperature, sorry rate of the reaction increases rate constant increases and rate of the reaction increases. It is initially observed by went off the Dutch chemist, and the relation of K and T rate constant temperature is given by Arrhenius. Okay, so right on the relation of rate constant and temperature is given by Arrhenius and this equation, which relates rate constant K and temperature is called Arrhenius equation. It is equals to a e to the power minus E a by Rp. This is Arrhenius equation. Okay. K is the rate constant all the terms you write down K is the rate constant we know already a is we call this a as frequency factor frequency. We also call it as pre exponential factor pre exponential factor, or we have one more name here that is Arrhenius factor. K is activation energy, R is the gas constant, E a is activation energy, R is the gas constant universal gas constant T is the temperature. Copy. Okay. Now you see, if K one and K two and K two are the rate constant T one and T two temperature respectively. Then can we write this ln K one is equals to ln A minus E a by RT one. Yes, equation one. Okay, ln K two is equals to again ln A minus E a by RT two. This is equation two. If you subtract one minus two, the expression you will get ln K one by K two is equals to E a by R one by T two minus one by T one. This is the expression we have. I memorize this and this expression like this since I have started with one by T two here. So here also I will place K two T two. So K two here. Okay, and then if you convert in log, so I'll write on log of K two by K one I'll write on here. And once I write K two by K one, this side will have a negative sign E a 2.303 R one by T two minus one by T one. So here if I start with K two, here also I'll start with T two. Here if you start with K one, then with a negative sign outside here also you can you can start with K one T one. Okay, so this is how I memorize this expression. Remember the similar kind of expression we have discussed in chemical equilibrium also. Yes. And how do you remember that. Right. Yes, tell me this equation is mostly there for irreversible reaction in chemical equilibrium chapter. If you go back and recall. So instead of this E a will have delta H over there. Yes or no. Yes. Right. This is very important because now that you know, because we are doing chemical kinetics you definitely know this fact that this came in K two are the rate constant. And if you do not, you know, focus on the difference in the two reaction. Right. Then in the exam if you get this expression you'll get confused that whether this K is rate constant or equilibrium constant. Yes. So how do you differentiate the two. If here delta H is written. This expression is given for reversible reaction. And then with delta H, this K one and K two are the equilibrium constant at two different temperatures. It is not the rate constant is clear. Write down this in your notes. Okay, in your own world. If delta H is written over here. It means these are the equilibrium constant. If A is written activation energy, then K one and K two are the rate constant. It is not equilibrium constant and then expression is valid for irreversible reaction. I said, if your delta H is written, it means K one and K two are the equilibrium constant. If he is written, then this K one and K two are the rate constant and this relation is for irreversible reaction. So if you get this relation, I'll write down this side also. Relation is ln K is equals to ln A minus E a by RT at any temperature T. So first of all this a and E a are collectively called activation energy and Arrhenius factor. The second term collectively called Arrhenius parameter Arrhenius parameter. If you draw a graph over here graph of log K rate constant and one by T on the x axis. The graph would be a straight line like this with a negative slope. And what is the slope over here? Tell me the slope minus E a by R, minus E a by R where R is the rate constant. But this is not correct. Why this is not correct? Because I have taken log K it's not ln K. And this is the mistake you made in the test also. The slope is this. Because this is log K it's not ln K. Yes. So keep this in mind. These things you don't have to memorize. I would say that just keep that Arrhenius equation in mind K is equals to A to the power minus E a by RT. From there you can derive everything. If you try to mug it up then this kind of mistake possible in the exam. So this is the temperature dependent relation we have. Okay. And this also like no few questions they ask. Very basic and easy questions I'll show you one question I'll show you. They'll give you this kind of expression and they'll ask you to find out based on the same relation Arrhenius equation you can get 23 kind of question 23 types of question. This is one relation. The only thing is a bit calculating calculation will be there in these kind of questions but it is very straightforward. You see this one. Option A you are getting. I think D is the correct. Are you getting D anyone? Oh yeah D. Okay. Just you need to equate and you need to solve this. Okay. Nothing much. That's the calculation we have here. So K2 you equate and then you take log and solve this. Yeah. So for K1 is equals to K2 will have 10 to the power 15 e to the power minus 2000 by T is equals to into this equals to 10 to the power 14 e to the power minus 1000 by T. So you cancel this out and take Alan both side. So you will have Alan 10 is equals to 1000 by T 1000 by T. Okay. So which is equals to 2.303 log 10 so T is equals to we'll get 1000 by 2.303 so 400 something 434.2 Kelvin we get. And another type of question is what they'll give you the expression of this log K is equals to some value they'll give minus some value into one by T like this. Okay. So they'll ask you to find out the activation energy here. So this term is nothing but e by 2.303 R. So whatever term we have here you equate this e by 2.303 R. You will get the answer. And no very basic questions you'll get. Okay, you won't get any you won't have any difficulty in this. This is the temperature factor we have. Okay, for affecting the rate of the reaction, it affects the rate constant and then the rate of the reaction. Now the last part here, the last term or the factor which affects the rate of the reaction is the catalyst. What is catalyst catalyst is the element or substance which changes the rate of the reaction, it changes the rate of reaction without taking part in it. We know catalyst does not take part in the reaction. Okay, it just affects the rate of the reaction, it can enhance the rate or it can reduce the rate also both ways possible. It depends on the nature of the catalyst. So we have two types of catalyst. The first one is positive catalyst and the second one is negative catalyst, positive catalyst, negative catalyst, positive catalyst right down. It increases the rate of the reaction. It increases the rate of the reaction by decreasing the activation energy. So it decreases sorry it increases the rate of the reaction by decreasing activation energy. So basically, in presence of positive catalyst what happens activation energy decreases. If you have a reversible reaction, I'm taking an example of it, reversible reaction if you have, then the catalyst the positive catalyst will enhance the rate of forward as well as backward reaction. Right so it increases RF rate of forward reaction and RB rate of backward reaction both it will enhance and hence it will achieve the equilibrium sooner. That is the reason you know use of positive catalyst we have. Suppose we have N2 plus H2 gives NH3, reversible reaction. If you want to increase the production of ammonia, then we use the positive catalyst so that the, oh I'm sorry, this is this we cannot take it, ignore this one. Because it does not affect the amount of product and reacting to I was thinking something else. Anyways, so if you want to achieve the equilibrium sooner, you can add some positive catalyst. So it's not like it will always affect the forward reaction. The reaction is reversible. So both way, the rate of the reaction increases by decreasing the activation energy. So purpose of catalyst or the effect of catalyst is what it decreases activation energy positive catalyst and increases the rate of the reaction. If you have negative catalyst so it is exactly opposite negative catalyst increases the activation energy activation energy increases and when activation energy increases the rate of the reaction decreases ROR decreases whether it is forward or backward ROR decreases. If you look at the graph here this y axis is the potential energy energy or potential energy and this x axis is the collision frequency you can say or collision number we can say or we can also say progress of reaction x axis. So we have a graph. Okay, we have certain energy of the reactant will go to a maxima and then wait. So what is the reaction I'm assuming exothermic anything it could be you coming into coming anything it could be here it is exothermic this is a reactant. And this is the product. So this much amount of energy releases. Now if the reaction is taking place in presence of a catalyst, it may go like this goes to a maximum initial and final stage will be same in terms of energy. Okay. And if you have one more catalyst it may go like this. So here you see this energy here. This energy is the activation energy. So, this graph, the orange one that I have written here. This graph is with negative catalyst, this one, negative catalyst, and this green one is for positive catalyst, and the white one there is no catalyst present here for this one without catalyst. This distance that you have here from this point to this point. This is the activation energy of the reaction. This distance. Right. This point we call it as activated complex. Okay, the reactant molecule collides. It forms an activated complex which has the maximum energy, and then it converts into the product. Okay. This is the activation energy of the reaction. This energy here you see this difference that we have here this difference. Right. It is the activation energy in presence of positive catalyst, because the activation energy the positive catalyst decreases the activation energy. And if this gap is less, the energy gap between the reactant molecule and the activated complex is less, then the particles can easily overcome this, and hence the rate of the reaction increases. This is for positive catalyst activation energy for positive catalyst decreases activation energy. And this the white one that you have is for activation energy is for negative catalyst. This decreases the activation energy. So that if the energy barrier is more than it is difficult for these particles are reacting particles to overcome this energy barrier and forms the product. Hence the rate of the reaction decreases. Understood. So I don't understand all the x axis. Sorry. So the x axis. The x axis is called as a number means, you can say it's called in frequency. I think when the two molecules collides support your time if more number of molecules collides. So college and frequency is more, or simply if you are getting confused you can also consider this as progress of reaction. This is nothing but the energy to react and converts into product time you can write or progress of reaction also you can do same thing. So that means we need to understand in this graph terms we have energy terms that is threshold energy and all will discuss that in college and theory will come to this graph again. Before going into the college and theory will discuss reaction mechanism. Okay. What is reaction mechanism how do we draw the graph and with that's what all things we can conclude. Can you copy this one of you?