 So, yesterday we have been discussing, discussing about kinetics, right? So, not yesterday, the day before yesterday, okay, okay. So, we told that this will be F1, in general, C A T E, okay. I think we have thoroughly understood what is this F1 T, because whatever format you use, somehow with simplifications and all that you will only end up with Arrhenius equation, okay. So that is why that is fixed for us, only Arrhenius equation is valid and I think no other time we will go beyond Arrhenius equation, right? For temperature how it affects K value, Arrhenius equation, right? Good. So now the second one, I have written for, okay, F2 C A format will be, I have written as 1 and C A and all that, okay. 1 C A, C A square, C A cube, all that we have written and that was only for A going to R, products, okay. Good. So that is one format for us and then, I think already those things we have written already, right? And also it need not be same simple C A square or C A cubed or C A to the power of N also we have written, where N can also be an integer and we have also written Michael S Menton type where C A by M plus C A or it can be C A by, it need not be Michael S Menton equation. You know at the end we can also have, this is C A square by M plus C A or C A by M plus C A square. That means what I am trying to say is that you cannot say that what form you will have unless you do the experiment, okay. That is the message finally for you. Good. So this is A plus B. Now I can have also various types of stoichiometric equation. It is not that always you have only A going to R. It can be A plus B going to R or it also can be A plus B going to R plus S. Otherwise you can write anything I say because now it may be 2 A plus B going to 2 R plus S, right? Even here it may be 3 A plus 2 B going to 1 R, right? So like that any combination is possible. Not only this, unfortunately we also have another category, this one R plus S. What is this? Reversible reaction. Now again any combination, this is 2 A, it may be B, it may be half R, it may be another 2 or 3 S, right? I mean if I write for example like this 2 A, 3 B may be, okay, this is again may be R and this may be 3 S, 3 S. If I say that what is the order of this reaction, what is your answer? 2 A plus 3 B going to R plus 3 S in reversible direction, what do you think? Why? Because they are telling, why it is non-elementary? If it is elementary what is the order? That is not possible, you know because I think nature wise 3 molecules coming together and then colliding itself probability is very, very less. 4 coming almost 0 and 5 coming almost almost 0, okay. So that is why you know that should be some kind of non-elementary type. Maybe you may end up with first order or second order, that is also we do not know. With respect to this it may be first order, with respect to this also it may be first order. But message is that all the time unless you do the experiment, unless you solve the problem on your own you cannot know what is the order. That is the message. And unfortunately that is why I think you should appreciate me. You do not appreciate me anytime, you know. So why I am telling you should appreciate me is I told that kinetics is very difficult and contacting is very easy, okay. How many reactors ideal things I can imagine in my mind? Only 3. That is all. You cannot add anymore. Even if you add it will be part of these 3 only, okay. But how many equations like this we can write another type I am going to write now. A going to R, what is this reaction? Parallel. Now again you may have A going to R going to S going to T, series reaction. Now you can have another type A plus B going to R and R plus B going to S, series parallel combination. So but unfortunately Gopinath I think for everything, every reaction like this you have to find out kinetics. Kinetics means rate equation. What kind of rate equation you have? That is why I tell it is hell because I think kinetics give you hell whereas contacting gives you very simple information only 3 and that too when you imagine ideal conditions much more simpler equations, correct, no, much more simpler equations absolutely there is no problem in understanding contacting patterns and you do not have to understand anything in the input. It is a market survey. What do you understand? You go to market and then how many people you have headache in the world? Find out total number multiplied by you know per 1 tablet. They have to take 3 tablets per a day, okay. Too much headache. So maybe how many grams normally it will have? All of us know because every time some I think till now there is anyone who has not taken any headache tablet. You have not taken? You also not taken? Why you have not taken? You do not get headache but head is there? Head is there. I do not know I think if you have headache I think you should get if you have head is Rahul. I think you should get headache I say. I do not know without headache I do not know. Yeah you also do not get. You are abjith, no? What about you? What about you? You do not get headache. I cannot tell you. Otherwise why do not you tell us? What do you do? Then mutation. I watch movies or TV or something like that. This is very good I say. We get headache once you see TV only he is a dick will go if he sees the movie very good nice ok anywhere so 500 mg into 3 1.5 grams a 3 tablets if you take so how many people multiply then you will know what is the fnr i mean fnr means again that is the product you have to convert that into stockahmetrically what is the input and then finally you will get so that is also no problem problem is here only that is why in the kinetics and you do not have any theory for all these things when you have only experiment right so what do you do generally in experiment what we do is for example if I take okay this equation A plus B right and then A plus B we will mix together in a any reactor can be used in fact right let us say simplicity is batch reactor both you put and at time t equal to zero you start the reaction when you put itself in the temperature and all that if you maintain and suddenly pour these two reactions there at 100 degrees for example so the reaction starts and take the samples at every time okay that timings and all that for every reaction you have to determine if someone is taking that reaction time you know that sampling time in one minute in one reaction does not mean that you know everyone should use only one minute in the world if you go to biochemical reaction you have to use one day one sample because the microorganisms like us so lazy they also would not work okay so that is why I think you know it may take that is why the proper sampling time always depends on the type of reaction and you do not know how fast it is how slow it is so that is why in the beginning it is trial and error you take one minute one minute one minute you will get may be only one percent conversion okay that means that ten minutes is not sufficient then you take five minutes five minutes five minutes five minutes ten samples it goes to one hour right fifty minutes okay so then still if the conversion is not conversion means you know the amount of A our key reacted so how many moles have been converted if you are able to find out if it is not again eighty percent ninety percent conversion again you have to change the samples sample timing so that is why it is not that easy in fact in laboratories we are spoiling your brain because in laboratory also we say that everything is given spoon feeding Indians are very good in spoon feeding correct I mean starts with our LKG onwards you know not even LKG from the time they stop taking mothers milk you know from then onwards we take a spoon and then feed in the mouth correct we mix a forexa forexa oh I you can find hundred I say I know only forexa I think if a forexa baby which baby is that shalak baby I thought you say shakalak baby there is a song you know that shakalak baby or something you say what is that movie a mothalwan yeah right mothalwan mothalwan I think that there is a computation also that baby food and all that yeah this is a dictionary I opened now encyclopedia tell me forex baby some computations are there yeah but that is for only baby food it is a brand name no no not baby food yeah forex baby food is there I think some other food also is there naan sir lak what is that naan naan naan this I have not seen ok ok so like that you know why did I tell that spoon feeding yeah true that we remember because that is the only thing we remember so that is why we are spoon feeding too much in the laboratory also start with you know these two reactants you take and reactor is already given one later or something and then we specify take a so much amount b so much amount maintain this temperature everything we are telling I think you know anyone can do you need not have a b take degree to do that the way we are telling in the laboratory correct no every instruction is given so whoever is able to read English they can conduct that experiment that is why I was also telling my students you know the difference between mechanic and you is mechanic also take the reading you can beautifully you can take the reading right if you are able to if you are not able to use your brain but the student brain comes only when he is trying to interpret the results ok something is increasing mechanic cannot tell of course mechanic if he has eyes he can also say that when you move this direction this is also increasing but why increasing is very important that is where the student knowledge comes right that is one part and without mechanic if I ask them ok you construct your own column like I am telling you in this batch reactor also you take your own batch reactor and then you know you have to decide now which batch reactor means it can vary from zero volume to infinity volume theoretically speaking correct correct no yeah so which volume you choose right and also a and b what are the quantities you use what are the temperatures you use correct no and when you are taking sample what do you do with that sample you drink or what do you do you have to analyze so what kind of analysis you use right is it hydrometric analysis or it is only hydrometry all the time or you can also go for some color removal color change if there is a color developing during the reaction the moment you put a and b both are may be white color or water color then when the reaction is starting so then it may become a slightly red and more red and more red that intensity of the red is increasing if you are able to characterize that red through some other probe some other mechanism of measuring so then with time how the color is changing now that color is a function of concentrations correct no because reaction is taking place concentration is depleting or product concentration is increasing all this you have to think why it is not need not be color you know when pH is continuously changing during reaction pH measurement can be done conductivity thermal conductivity you put the thermal conductivity probe inside and then one minute two minutes three minutes four minutes you don't have to even take sample conductivity measurement conductivity probe directly connected to computer that will record with the time the moment you switch on the computer and then start the reaction and you know switch on and the data transfer there so continuously it is increasing or decreasing or whatever your measurement so conductivity now before okay at least before doing or after doing this conductivity measurement you should have a relationship between what are the number of moles and what is the conductivity that is what we call calibration chart you heard of it no calibration chart so that calibration you have to make in the beginning itself so that means one mole means this is the conductivity 1.5 mole means this is conductivity two moles mean this is conductivity I am talking about moles of one reactant key reactant okay so that is why there are so many methods so many methods that is why the foreign education is much much better than our education it is not that much spoon feeding in B take level I think they are also not that good but at particularly PG level you have to learn everything on your own everything on your own that is why they also give less number of courses and more work I think now that is why we also reduce you know we have only five courses you know yeah of course for MSP HHS college is only one or two so that is why that number of courses also now we are reducing in fact our department started reducing we wanted even four so that you know you you take less number of courses but give more work for them then only you learn so that is why I tell you this is real hell and I will come back to this one you know yeah anything I missed apart from this kind of reactions any other kind is there these are all homogeneous either gas gas or liquid liquid okay either gas gas or liquid liquid right yeah so now heterogeneous I will go but what about this one I think any other thing I missed of course I correct I also covered reversible reactions reversible reactions also can also be of course very simple type these are all professors favorite A going to R and A going to R reversible that is all we do not go beyond that more most of the time so all other things are given to you to do yeah that is right autocatalytic reaction which normally we write when R is the product R plus R okay this R is the product but unless you have some product in the beginning initially this reaction will not start or otherwise you can deliberate to add and it seems there are many reactions particularly in organic reactions where you wait for some time somehow one or two molecules of R will form okay and then onwards it will autocatalyses the thing the product so that is also another type so like that we have all kinds and unfortunately what your job is that every time you look at a reaction rate you cannot tell what is the order of reaction that is what is the answer if I tell you that A plus B going to R what is the order of reaction right you say sir we cannot tell unless you tell me whether it is elementary or not if it is not elementary and if I say I also do not know whether it is elementary or not then only possibility is doing experiment okay so that I will come back again because I think heterogeneous systems next semester only I will do it but to give you a flavor because in my diagram that entering leaving and kinetics contacting in the diagram there is physical kinetics and also chemical kinetics that you remember so I think now itself it is better to have some idea about what is the meaning of this physical kinetics that will come only for heterogeneous systems so that is why I will give one or two examples of simple equations how do you develop for heterogeneous system and I will also explain the how our brain has to use I mean used to be used for developing this rate expressions homogeneous it is very simple I do not have to imagine much why I take A and B I stir it and by my definition of homogeneous these molecules will be beautifully mixing together at molecular level itself they are mixing very well on the top of it I am also putting another extra stirrer and then mixing if it is gas phase much easier to mix also right even without mixing also you have the good mixing that means in homogeneous instead of saying it is one phase what you have to say is the molecules are available for reaction if it is A going to R you do not need any other molecules okay all A molecules are simply decomposing provided if you have that sufficient collisions sufficient conditions inside the reaction to take place those are all called decomposition reaction A decomposing to this I have not there okay here also I can tell A decomposing but reversible reversibly decomposing to R our imagination is that even this A A molecules will come to because all these things are randomly moving even in liquid also molecules move right so when they are moving and then colliding with each other and when they attain sufficient activation energy right that is why when you increase the temperature what will happen number of collisions will be increasing more rapidly they are going and colliding right activation energy will not change but quickly that activation levels are reached quickly because of high energy in the in the molecules now because at high temperatures so those things will come together collide and then reaction will happen right that is what our imagination good so if I have A plus B also same thing two molecules will come and all that other than that I do not have to think but only thing is is there A molecule by the side of B is there a B molecule by the side of A so that it need not search okay so that is homogeneous reaction I do not have to think much now the moment I go to heterogeneous reactions heterogeneous reactions we have given already the classification right so it can be either gas liquid gas solid liquid liquid solid gas liquid solid solid solid these are the five six categories you cannot have more than that what are the things start with GL gas liquid gas solid liquid liquid solid solid solid liquid liquid liquid liquid liquid also what gas liquid solid these are the things these are the possibility that means there is one reactant if I take yeah the simplest cases I take the simplest case is gas solid it is not only the simplest but more more number of gas solid reactions we can see in chemical engineering problems okay more number of gas solid reactions and this gas solid reaction again can be catalytic catalytic or non catalytic okay one example of catalytic quickly one example of catalytic reaction Ammonium Ammonium synthesis Srikhanda you are Srikhanda Srikhanda right yeah tell me Ammonium synthesis what is the catalyst okay so any other one because most of the time we know only two reactions Sulfur trioxide but what is the catalyst there very please remember I think at least two reactions we remember right we design so many reactions but I think at least two catalytic reactions when someone asks you okay what are the catalytic reactions you can tell non catalytic reactions coal combustion coal gasification okay and other reaction other than coal no resting is okay yeah I think resting we don't know how to do anything okay it will rust anyway so that is not the one other than resting how do you make iron from iron ore you see you see how mad you know we are in in knowing things where did you study acetica it doesn't matter I am not blaming you I am not blaming institute but I am blaming our wonderful education system which we developed in this country for the last 20 years earlier it was slightly better okay good so I will give you that other example because this also you have to remember this is non catalytic carbon is one thing coal plus C plus O2 giving you CO2 that the simplest one that only I will take but we also have you know this iron ore reduction there are two types of ores in iron do you remember magnetite and hematite okay can you tell me hematite formula magnetite because H comes first so remember F2 M comes later and remember F3 that is how I remember otherwise I also get confused understood no what did I say hematite comes first so that is F2 because 2 comes before 3 yeah so M comes later magnetite F3 F3 O4 and F3 O4 and F2 O3 okay now which one you choose F2 okay F2 I choose because democracy F2 F2 O3 solid plus what is the gas oxygen it is a reduction reaction actually hydrogen CO also can be used okay but hydrogen let us see CO means 2 I have to write at least H2 1 1 1 I write okay so this one is F3 plus H2O this is gas this is solid again okay balance this is 2 this is 3 this is 3 correct Swami yeah Swami is expert in order of reactions what is the order of this reaction you do not know or what is that 4 molecules are there can it be elementary so yeah it is a non elementary so that is why we have to again find out the rate equation for this means it is hell okay good so now this is one part you know first I think you know the gas solid reactions itself you have catalytic reactions and non catalytic reaction and now you have to imagine the process in catalytic reaction what is really happening that means the entire process should be in your mind when I say catalytic reaction your mind should go to a catalytic reactor first correct you are using a catalytic reactor what kind of catalytic reactor you can use we have only two types plug flow and mixed flow right and when you are defining plug flow and mixed flow how many phases you have taken there there there earlier only one phase right yeah that is why I told you that ideal conditions we are only discussing for homogeneous system only one phase now I have two phases that is why blindly I cannot say that you know I will take plug flow the question comes what phase you want to have in plug flow right what phase you want to have in plug flow right so that is why when I take for example catalytic reactions which you know which you told as iron ore no not iron ore what is that ammonia synthesis ammonia synthesis now I have to imagine my column and most of the time this catalytic reactions are conducted in which reactors packet beds packet bed reactor why what do you mean easy contacting what is difficult contacting tell me I think that way I can ask yeah okay what do you mean by uniform contact yeah you see 90 percent of the time what we use our words are waste words or otherwise we don't know the meaning of them when we are actually using them I am not blaming you including me because if you take the efficiency of people how many words they are using in a day and what is the meaning of all these words if you count I can tell you 99 percent our our words are meaningless in a day you can count you write every day record everything evening you analyze okay so that is why everything can be questioned he said uniform I asked what is uniform uniform contact then what did he say afterwards now we change it again what is fiction contact thing no not impressive yeah anyone else try no but I think Abdul is bold enough to say whatever he knows everyone of you should be like that you should be bold enough to say whatever you know then it is for me to decide whether it is meaningful or no meaningful if it is not meaningful I will tell you okay uniform the moment you say that means each and every particle should be exposed to the same concentration okay so is it possible in a packet bed why it is not possible because it is a lengthy column you are sending gas either from the bottom or from the top and the first contact is for the first particle which is staying at the top or bottom the way you are so there is no uniformity and the last particle may not see this gas for sometime so that is why but whereas if you say mixed flow like you know fluidized beds are called as mixed flow reactor fluidized beds I hope you know what is fluidization all the particles will be vigorously moving okay you don't have to put extra stirrer so because gas itself will move the particles here and there jumping through okay then what you said uniform contact is better okay so good so in a okay nothing let me let me try now itself I will try to explain okay this is the packet bed I asked you why we should use packet beds I also told this it is not unreasonable question because sometime back I also told you these packet beds are work horses packet beds are work horses of chemical industry so memory gone I think you are not able to retain those words I think these are nice words work horse I also told you what is the difference between work horse and running horse okay I mean all those things I told you only not to forget I say it is only for remembering okay only for remembering I am telling work horse because it is very simple to operate and it will work years and years without any problem whereas fluidized bed is not that easy to operate why inside particles are moving whereas here inside particles will not move the name itself is packet bed there it is fluidized bed that means you are you are making solids as fluid and fluid always moves correct no even water there is no glass here okay so in the water unless you put in the container the moment you break a container or put a small hole it close right that is the property of the fluid fluid has to always flow so that is why fluidization name came because of the reason because you are making otherwise solid if the check piece if I put will it cannot move it cannot move fluidization right now I am making this one you know fluid property so that is what in fluidization also we do we do we do not do why there but I think we use a compressor that will be very good first all research scholars do that for fluid we ever working in fluidization do like that I think by evening their face volume will be double okay yeah all these things you know that will go up okay anyway so that is what is fluidization right so that is why and when you when the particles are moving and because of the movement sometimes even the sides of the reactor will be eroded you know corrosion erosion okay slowly eroded means all the surface slowly depleted so all these things may happen that is very difficult to operate whereas this is not difficult to operate what we simply do is we pack all the particles not so big particles there is a ratio also okay then this is for example when I am talking about ammonia N2 H2 both are entering and this is Fe Fe Cat catalyst right then you will have here some NH3 and it is a reversible reaction you remember that no N2 plus H2 giving you NH3 is a reversible reaction so you may not have 100% conversion so that is why some N2 some H2 will be there so those things also I have to write N2 H2 all that will be there and now when I want to develop the kinetic expression for this heterogeneous system this is the system which I have to imagine first then my focus has to go to one particle somewhere here that one particle I will take it out so when I take that one particle out this is the one that particle out and now I have to imagine around the particle you see all this is imagination all this is only in your mind okay you close your eyes all the steps should automatically come that is what we say physics of the problem physical phenomena of the problem what is really happening unless you understand this physics what is really happening the phenomena inside you can never write an equation if you write an equation without knowing the phenomena the there is no use of that equation there is no meaning for that equation that is why every time please remember I think next time you will do transport phenomena also because the phenomena should be understood first and then only you start writing the equations so for that first of all you have to imagine the entire equipment first okay packed bed is this I am not telling you what is packed bed and all that because you have already done that two course I mean I know in B Tech level itself you should have known what is packed bed even otherwise packed bed is easy to imagine because packed bed is nothing but a cylindrical column with a distributor at the bottom and then top also another distributor you pack all the solids in between so that they should not move and student cannot imagine this distributor plate he thinks that it is simply because I have not drawn here distributor plate right so that is why he thinks that you know you can have solids just in the column somehow floating okay without moving the floating mountains okay so like that you may be imagining but distributed design also is very very very important in fact that is one of the crucial designs in packed bed operation you know the distributor otherwise if you put completely a plate like this yeah this is the plate circular plate and then try to send it through this or ammonia hydrogen through this can you say you cannot so that is why if you want to send you should have holes and what is the size of the holes if you put one micron holes or maybe one nanometer holes then what will happen why it is not possible why flow rate will not go I can I can also use very very big compressors and then push it flow rate also I can maintain yeah that is the one as engineer your mind should go to the pressure drop first why because you have to buy such a big compressor all the money whatever you get you are about to get as a profit will go to only design of compressor okay so that is why you cannot do anything you do not get any profit when you start a company so that is why the distributed design also has some parameters where you have to take what is the diameter of the hole okay how much is the free area all this you have done without knowing you know without knowing this you have also designed distillation columns where distillation columns have perforated plates not only distillation absorption columns also you have done okay yeah absorption columns also because you are bubbling the liquid through sorry you are bubbling the gas through the liquid so how do you bubble unless you have the perforated plate so that is why you know we never forget I know some of us most of us also as teachers we also never point out this I am taking more time because everything I am trying to point out at least once in your life okay so that is why we are you know not able to run with syllabus but I do not want to run if I walk with syllabus that is more than enough for me right so that is why you this also is very important all this on the top also right in fact in REC warangal when at the time it is REC warangal so when we were doing the laboratory there was a mechanic so some pump was not working in fluid mechanics lab the gasket has gone you know what is gasket between two flanges govina you know what is gasket really okay so when you are joining two pipes when you are joining two pipes you know what are flanges flanges also you do not know really flanges your chemistry or chemical you know what is flange okay how do you join these two pipes I have one pipe here one pipe here how do I join don't tell me you are going to weld okay that is one if it is permanent okay it is not permanent whenever I want I have to open and then again clean it and again join it so what do you do okay I have two pipes where do I put nut and bolt here around this I should have a flange okay so that means it should be something like this okay and this side also exactly same thing and this is the pipe okay and when I look in this direction at least once then it will be like this like this this means this is equal to this okay then you will have normally either 6 or 8 or 12 are put there positive I mean what is that even numbers so that you know when you are tightening it is uniform tightening will come there so that is what you do and then you will also have this side also similar type this is one like this another one here join these two and then tighten nut and bolt okay but this is metal and this is metal so when I just tighten without putting anything inside that metal metal contact is not perfect so that is why it leaks so what do you do now you put a gasket that gasket is normally is a rubber neoprene rubber or so where it is having slight elasticity so that it can be a little bit compressed right and then you also should have because you have to put in between this right nut and bolt also yeah this nut and bolt bolt also has to go through that so that is why you should have holes for even gasket also so our mechanic what he did was he put the holes for the gasket but he did not cut this portion so that means you know these are the two pipes where it is blocked actually okay and then he started pump no water coming in fact exactly same reason in ICI industry imperial chemical industries they were producing ammonium phosphate they use six tanks in series okay tanks in series model also we will see later six tanks they have used so in from I think third tank to fourth tank or so third to fourth maybe second to third so the gap between that you know the gasket started leaking so they stopped and without knowing that I think you know some new person would have gone maybe like you who just joined in the job so without knowing what is flying what is you know this gasket he has put that and then without any without any flow so then may have to sometime the pressure build up some explosion happened and that is one of the worst disasters before our own disaster flex burro name of that company name of that place is flex burro F E F L E X I B O B O R O U G H R flex burro okay that means these are recorded things you see now those simple things we never bother to know and if you get a unfortunately a job in chemical industry what will happen explode and okay nothing else okay and you know today's paper you have seen no very tragedy and you know most of the workers are untrained people poor fellows who are coming from the villages and then just they don't know they know how to you know crack the crackers but I think they don't know how to make the crackers so something would have happened and so many people died so that is why this training the thinking is very important right okay so those things also are very important for us yeah thinking whether I can continue or not okay so that is how these things will enter now I have to develop a rate expression means I should know what are the what is really happening in the column right so I know what is happening means it is entering it is coming out some of the reaction is taking place these things are coming now I have to focus a little bit you know more intensely on a particular portion my portion is one particle that is the I will take out so in this one particle I know that it is a porous particle right and fluid mechanics tell me that yeah here here also you have the particles and then you are allowing the flow to go how the liquid flows there or how the gas flows through the packet bed because you have interstices between particles we say voidage and all that right yeah so then if I look at one particle here the gas may be going like this then immediately there is another particle that will again split like this right on the whole if you look around the particle I have this flow I have changed the direction should have been vertical okay so this is how the flow don't get confused now this is drawn here vertical this is horizontal turn it like this that's all okay so this is the one and whenever you have the flow this is let us say in the beginning H2 N2 this also H2 N2 and we know that from fluid mechanics this will have a film around this whenever you have two phases there will be interface right and interface also will have one side one phase another side another film you know that is why what you call you know two film theory what is meaning of that same thing two film theory gas film and liquid film if it is gas liquid reaction but here we are talking about gas solid solid will not have a film inside so that is why you have only fluid film outside so this will be nicely written all the time like this even though then it never exists like that this is the film okay this is cat okay this is FE and this is film okay that is the film now what are the steps because you have to imagine the phenomena I have a particle I have the fluid flowing around that the gas flowing around that now what happens for the reaction to take place hydrogen and nitrogen they both have to first pass through this film that is what is you know mass transfer they have to be transferred through the film to reach where to reach the surface if it is non-porous particle non-porous particle that means there is no pores inside then all the reaction occurs only on the surface so now I mean now let us imagine that only surface reaction is possible then afterwards we will go inside so right now I am taking only non-porous FE solid FE FE means iron so non-porous iron so then the reaction is taking place only on the because it is a catalytic surface reaction takes place the moment hydrogen and nitrogen both go there in fact there is still more mechanism but for reaction for reaction rates to be developed we do not go to that level at engineering level but science level they go right in engineering level what I will imagine is H2 N2 both are going sitting side by side and then reacting and NH3 will come out right so now the concentration of NH3 on the surface is more or outside more NH3 exactly that is where the reaction takes place so more production of NH3 on the surface and outside there is no reaction there is no NH3 so that is why there is a gradient I told you know diffusion is a natural phenomena so wherever there is concentration gradients the things will flow in this in the direction because on the surface I have more NH3 and outside I have less NH3 it will simply come out it is now coming out through the filling now you see H2 N2 going in and sorry H2 N2 going in and NH3 coming out that is what what we say you know equimolar counter diffusion if I have same number of moles of A going in same number of moles of B coming out but in reality you will never have equimolar counter diffusion it is only in our mind for simplicity of the problem if you have you know that unequal moles entering and unequal moles coming out what are the equations you use here I can use fixula if I say equimolar counter diffusion and all that anyone did in transport phenomena or advanced mass transfer multi component diffusion you heard of Stefan equations Stefan Boltzmann equations no not for mass transfer there is I think Stefan equations I do not know what is the next name yeah Stefan equations I will find out okay yeah so those equations you have to use where that is used only for multi component diffusion but anytime you have used multi component diffusion simplification again so that is what so then equimolar counter diffusion that is what I am trying to say is through this we have to now find out what is the amount of NH2 or H2 sorry okay H2 and N2 entered what is the rate of reaction and what is the amount of NH3 come out so what are the three steps now reactants mass transfer of reactants through the film rate of reaction on the surface and yeah rate of we do not say desorption because desorption is on the surface but we are talking about only mass transfer through the film okay we assume that desorption adsorption surface reaction all things are as surface reaction only so that is what my next thing you have to go into those details again in reaction for reaction to occur first they should be adsorption then the product or not what is that intermediate formation okay then reaction then product desorption here product mass transfer through the film so now reactant mass transfer through the film product mass transfer through the film products and rate of reaction on the film on the surface sorry on the surface these three must be equal under steady state conditions then only the reaction can happen you see now to develop the rate how much physical phenomena I have to remember now the moment I know that yes what is the mass transfer equation through the film what tell me that is the simplest one which you learn in mass transfer first course mass transfer course you know first course may be for some of you equilibrium equilibrium stages yeah anyone quickly what is mass transfer equation Abdul Abdul is a bold guy I am not asking diffusion equation I am asking mass transfer equation both are different yeah okay in our so-called term N A equal to N A is molar flux mass transfer that one not diffusion okay that is equivalent to K into C A minus yeah but in this case if I say that this is C A B this is C A S then what is the equation yeah I mean I have C B that is entering because I have to write mass transfer difference only for reactant I cannot write reactant entering and product leaving no you cannot subtract one from the other yeah this is C B minus C A B minus C A S into K if it is gas phase we call normally K G this is equal to N A that is the equation now this equation must be equal to rate of reaction so rate of reaction if I have first order yeah C A S C A S because that is where the reaction is taking place C A S right and in my example of course here actually in ammonia example it is a reversible reaction where hydrogen concentration you know the reversible reaction also is possible but if I am assuming that I have irreversible reaction irreversible first order reaction then simply it is K into C A S otherwise it is again K into C A S nitrogen I mean you know those reactants minus products that kind of complication we are not trying to imagine now later we can imagine when you go to actual chemical and catalytic reactions so now this is the equation under steady state conditions this is what is minus R E that is not direct because again I have to solve for C A S and all that I have to stop here oh 40 minutes okay so we have to again close this saying that yeah C A S is not easy to take it so that is why C A S has to be eliminated all that I will do tomorrow just as one example so but my idea to you my explanation to you is so much I have told you the reason is that so much thinking is required for writing this simple equation