 Yeah. So we are going to start with diffusion and effusion. See the two term here we have one is diffusion, other one is effusion. First of all, if I tell you this effusion, effusion is the leaking of gas, right? Like the puncture or the, you know, when the football bladder burst, right? So effusion is what? Effusion is right on. It is the process. I'll write down like this way. Definition first you write down then you'll understand. Effusion is a process, is a process by which, by which a gas under pressure. This point is important. Okay, under pressure escapes from, escapes from the vessel from the vessel. Through a small opening, through a small opening, opening or orifice, small opening or orifice. So escaping of air from puncture tire. Okay, an example of effusion. Orifice is nothing but the small hole you can see. You know, a point that is, you know, purposely made to for the, you know, for the removal of gases that we can understand. Example is what? Escaping of air from, from a punctured tire, right? Football bladder also we can take. We can also take an example of perfume, escaping of perfume molecules. Okay, when you see the bottle of the perfume, there's a small orifice, right? When you press it, the perfume molecules comes out, right? That escaping of molecules, perfume molecules from that orifice or that small, small hole that we have, that process is effusion. Okay, so effusion is nothing but the escaping of air particles or any gas from a small orifice or opening. Okay, diffusion. What is diffusion you see? Diffusion is the process of, diffusion is, is the process of, of intermixing of gases, intermixing of gases, right? In this what happens right now, when the two gases, two or more gases, in fact, when the two or more gases intermix, intermix irrespective of, irrespective of their density, irrespective of density, density, and without any external help, without any external support we can say, without any, without any external support or help. Okay, so here we have it's spontaneous you can say, but effusion is what you see, effusion is under pressure. Okay, this is the basic difference between the two. Now, when you press the, you know, the knob of that perfume bottle through effusion, the perfume molecules comes out and when it comes out, it diffuses into the air molecule. Do you understand the difference between the two? Mixing of gases is diffusion, effusion is the leaking of gas from the small orifice. So when you press the knob of the perfume or deodorant, from the small hole the gases particles comes out, that is the process of effusion and when it comes out, it diffuses into the atmosphere and we get the smell from a certain distance, right? So that, the smell that we get at a certain distance, it is because of diffusion, but leaking of the gases particles from the bottle is effusion, right? When you cook something in kitchen, right? The aroma of food that you get into the living room or your bedroom, that is because of diffusion, okay? That is not diffusion, that is diffusion because the, you know, the smell that diffuses into the air particle, right? I hope you understand this definition between the two things. Yeah? Now, obviously do two different processes we have, effusion is something else, diffusion is something else, but while calculating the, while doing the questions on this, the formula and everything is same for the two processes. There's no difference into this, okay? So whether it is given diffusion or effusion in the question, you have to do the same thing for all the, all kind of questions here. What is the formula? We'll see that. See this? Write down, under similar condition, under similar condition, temperature and pressure, of temperature and pressure, the rate of, the rate of diffusion or effusion, the rate of diffusion or effusion of gases are inversely proportional, inversely proportional to the square root of their density. So we can write the rate of diffusion or the rate of effusion, whatever it is. The rate of diffusion or effusion is inversely proportional to the square root of density of the gas. So density is, you know, directly proportional to molecular mass, because density we know it is equals to mass by volume. So for two different gases, if I write down the rate of diffusion or effusion at the similar condition, so we can write R1 by R2 for two different gases is equals to density of two by density of one and the square root of it. This is the formula we can use, which further we can write in terms of mass, that is the molecular mass of two by molecular mass of one, square root of it. And molecular mass we can also find out with the help of vapor density VD of two by VD of one. Generally, vapor density we use when we have mixture of gases. This is the relation, one relation of the rate of effusion or diffusion. Understood this? Similarly, we can, how do we define the rate? Now you just keep it aside for a while. Okay, this relation that I have written, keep it aside. Now, in general, I'm asking you what is rate? Rate is anything divided by time? Like how do you define velocity? So rate of displacement per unit time, speed is distance travel per unit time. So rate of change of displacement is velocity, rate of change of speed, sorry, distance is speed. So whenever we talk about rate, it is per unit time calculation we have. Now, if you talk about the gases, we can define rate by the volume diffused. If volume is given that these many volumes diffuse in the given time, volume diffuse divided by the time required for this diffusion. Or we can also write the moles diffuse or diffuse anything divided by the time required for this diffusion. Or we can also write the distance traveled by the gases particle, distance traveled by the gases particle divided by the time required for this. Okay, just give me a second, somebody is there to know. Okay, so this is the relation of rate we have because you know this density, molecular mass and vapor density thing you can write on always. This relation will write as per the information given in the question. Then this and this we can relate and we can find out the answer. Okay, you're talking about this one? Yes, this is the supposed rate of two different gases, right, at the same condition, same temperature and pressure. So R1 by R2 is the rate of one gas divided by the rate of the other gas is equals to the density relation, molecular mass relation and vapor density relation. Right, and for any gas rate always we can define like this. It's not about the rate anything we can define like this. Right, for a given gas oxygen we say 10 milliliter of volume diffuse in two second. Right, for example, we say a gas any gas a gas diffuses 10 ml in two seconds. Right, so what is the rate for this gas? What would you say that the volume diffuses divided by time that we say that it diffuse 5 milliliter per second that is the rate of this gas. And this rate we can define we can relate with any one of this relation whatever is required. So sometimes in the question they'll give you volume, sometimes they'll give you moles, sometimes they'll give you distance. So whatever the relation given in the question you can take it here and this any one of these things we can always relate with the molecular mass of the gas. I'll give you some question you will understand and what is the point I'm talking about, but rate we define like this. Okay, now suppose I'm taking for reference suppose volume is given in that question, then there are two possible cases we have this is possible with moles also this is possible with distance also. So case one is what case one is when we have equal volume of gas, equal volume of gas diffuses in diffuses in different times, like the T value is different. Right, so what we can write for two gases we can write R1 by R2 is equals to the volume diffuses for R1 V divided by time taken is T1 V divided by time taken is T1. Okay, this equals to we can always write the molecular mass of the gas to divided by gas one this we can equate like this. Okay, since the gas is given so you know the molecular mass, so you will have the relation of time that is T2 by T1 is equals to M2 by M1 root of this we can equate basic logic you don't have to memorize this basic logic you can apply you'll get the answer. Suppose the second case we have just opposite of that different volume of two gases, different volume of two gases in equal time means T value is same. Suppose if we have R1 by R2 is equals to V1 is the volume divided by time T V2 is the volume divided by time T is equals to again we can write M2 by M1. This is equals to V1 by V2 is equals to M2 by M1 root of this is the relation any doubt in this clear then so this is the two possibility we have two more condition will see which is not in general the case we get in the in the exams but yes if it is there then what we have to do we'll see see these two formula that we've seen seen till now. This is under the same condition when pressure and temperature is constant. Okay, what happens when pressure is not constant. Okay, so write down this two relation here. 99% of the cases you won't get this in the question, but yes it is there so you should know this. If pressure is not constant. If pressure is not constant and we know more pressure more will be the diffusion or diffusion. If the pressure is more than what we can write rate is directly proportional to pressure. And we already know that rate is inversely proportional to molecular mass this relation we have already seen when we combine the two will have rate is directly proportional to P by root M and hence we can write if pressure is not constant R1 by R2. Is equals to P1 by P2 into this is the relation we have if pressure is not constant. So pressure is not constant but here we are assuming temperature is constant and we can also write next if temperature is not constant is not constant. But pressure is constant pressure is constant so more temperature we have more kinetic energy and more kinetic energy means more will be the rate of diffusion or diffusion. So in this case also we can write rate is directly proportional to temperature and again we already have this relation. So if you combine that two will get great is directly proportional to T and inversely proportional to M and hence R1 by R2 is equals to T1 by T2 root over M2 by M1. Remember this M is the molecular mass of the gas. The gas is mentioned molecular mass is given copy this document one second idea. Ah mother which two equation you are talking about. No we see when pressure and temperature is constant then it has no role we have the relation before this we have discussed. Right it has no role so we don't have pressure and temperature term over there in the expression is just R1 by R2 is equals to root under M2 by M1. Yeah Aditya for diffusion we don't require any external support any external agent we don't require means the process of diffusion will happen without exerting any pressure. Right you see I give you the example know the aroma of food right when you cook something in the kitchen we don't have any pressure once the you know once the molecules releases in atmosphere after that diffusion takes place. So for that the process of diffusion is what it is intermixing of gases see one thing here for diffusion we have two steps actually if you take the example of perfume or deodorant right. So once you press it the molecules comes out this the molecules comes out is a fusion so once it comes out after that diffusion takes place are you getting it. So for a fusion we require pressure so more pressure more will be the fusion and hence more will be the diffusion. But for diffusion we don't require any pressure because the process of diffusion is intermixing of gases. Yes respond please yes yes yes we can say that more diffusion will be there so more gases will come into the atmosphere and hence more will be the diffusion. Now we'll see some questions based on this these two formula rarely we use OK mostly they won't give you know pressure and temperature no variable mostly they'll give you these two as constant. So this formula that we have already discussed before this this is more important this one this formula is required. Now we see some questions here try this one. Yeah that's right. Yeah that's right. So simple one you see 50 ml of H2O2 is allowed to diffuse through an effusimeter till the residual gas occupy 90 ml. OK so initial volume you see the initial we have is 100 ml right residual gas means the gas which is left so volume of the residual gas is 90 ml given in the question. So volume of effused gas is equals to what initially it was 100 90 is present now it means 10 ml has been effused. OK so we can write the rate of diffusion of diffusion of H2 by rate of diffusion of O2 is equals to the molecular mass of O2 which is 32 by 2 root under and that is 4. This is the ratio of the rate. Suppose X ml of H2 diffuse and it means 10 minus X ml of O2 will diffuse. So we can write for the rate as X divided by the time required for this diffusion and this time will be same for oxygen also that would be T and this is equals to 4 we have. We can solve this for X and X you get from this is 8 understood means the volume of H2 diffuse is 8 ml. Hence the answer for this question is volume of H2 effused is equals to 8 ml volume of H2 left that is the residual. 50 minus 8 that is 42 ml volume of O2 effused volume of O2 effused that is how much 2 ml then volume of O2 left is equals to 48 ml and this is the answer for this question. Any doubt whenever you get this question of diffusion and effusion only this you have to do take the ratio of rate equate this to molecular mass and the data that is given here. See here is the data is given in terms of volume we have taken volume. Sometimes what happens they'll give you the number of moles here the number of moles you have to equate with the volume clear understood no doubt. Obviously you see for effusion will have we must have the pressure difference. So the moment when the pressure becomes equal both side there will be more no effusion and effusion always happens when we apply pressure you stop applying pressure external pressure. There won't be any effusion but condition if you talk when the pressure becomes equal both side then the gases won't diffuse. Okay one more question you see this kind of question they have asked in JXM okay I'm not talking about the exact question but exactly same pattern okay data will be different. This one you see try this yeah approximately 81 yeah that's right approximately 81. Okay you see the question is what we have a cylindrical tube and the length of this tube is given that is 200 centimeter okay cylindrical tube length of the tube is 200 centimeter. This is the two inlet we have here this is X for example and this is Y and this distance is given that is 200 centimeter. Suppose this is X inlet and this is Y and this distance from this point to this point is 200 centimeter. Okay now from this side we have HCL gas we enter HCL gas from the this side X inlet and S3 gas through the inlet Y that is from the right hand side and S3 gas like this at the same time. White fume first appears at point B inside the tube okay so white fume is what suppose we have the reaction of NH3 and HCL. So when this NH3 and HCL reacts this forms NH4Cl and this reaction gives white fumes okay basically white smoke kind of things appears which confirms that NH3 and HCL reacts somewhere here. Okay so point is what this white fume means NH3 and HCL meet at one point and then only the reaction takes place which gives the white fumes. Okay so obviously both will diffuse from the two end which one will diffuse more what is the molecular mass of NH3? 17 molecular mass of HCL is 36.5 okay so we know rate of diffusion is inversely proportional to the square root of molecular mass means we can say the rate of NH3 is more than to that of HCL. NH3 is more than to that of NH3 and hence what we can say NH3 will diffuse more than HCL. So suppose here the point P we have somewhere in between this two end here we have a point P where the NH3 and HCL meets. So this distance I am assuming I am assuming this as you know some distance suppose Mahalo it is what we can say it is D and this one is then 200 minus D right so this is D so this is 200 minus D and then we can apply the rate of you know rate equation here. We need to find out the point P from the distance x so it means we need to find out D here. So what we can write the rate of rate of HCL by rate of NH3 is equals to first of all will write down the molecular mass of the two gases 36.5 root under. And this would be equals to what the distance travelled by HCL that is D time is same that is 200 minus D. We can solve this for D that will be a answer okay so this is 2.25 and 2.25 the value is we will get here 1.5 isn't it D by 200 minus D. And when you solve this D you will get approximately 81 centimeter answer is this any doubt in this any doubt in this tell me. Enjoy the question that they ask they have given the question like this they have given three points here in between the in within the slender one point is exactly at the middle of the slender. One point is exactly the middle of the slender one point is this side and other point is this side and they have now they have named this point suppose P Q and R at CL and SC and the first question was that at which point P Q or R the white fume appears. What was the answer what will be the answer here you don't have any of the info at which point the white fume appears ideally how do we do that this is the half of the tube. Right and we know the diffusion of NS3 is more than to that of HCL right in the same time so obviously this NS3 will cross the half portion of the cube half of the distance length of the cube of the slender. And NS3 will cross this side and somewhere in this region, half of this region, this, you know, half of this cylinder, this site of HCL, NS3 and HCL will meet because of the more rate of diffusion of NS3. Hence, the probable answer should be P as the given information as per the given information that question. The answer is P and then they have asked in the second part of this question that what is the distance from this end of P where the two gases. Yes, so this is the rate of diffusion and diffusion you will get some more questions on this similar pattern only just need to equate and you'll get the answer okay that you will get an assignment and so on that. So next we are going to start the next part the second part of this chapter that is the real gas.