 Okay tell me have you solved this question quickly what is the answer 4.69 you are getting okay the first one is correct it is 4.69 okay and how do we do that you see the number of suppose if I write down here the reaction is CS3 COOH COOH plus NaOH gives you CS3 COONA plus H2O right so 0.1 into 100 so we have actually here 10 millimoles of NaOH 10 millimoles of NaOH and for CS3 COOH we have 20 millimoles so 10 millimoles react with 10 millimoles of this right and gives what 10 millimoles of CS3 COOH so this is what this is the limiting reagent in this reaction NaOH right when 10 millimoles of this react okay yeah 4.69 is correct when 10 millimoles reacts so 10 millimoles of CS3 COONA forms now in the reaction vessel you see we have CS3 COOH present and number of moles of CS3 COOH left is what number of millimoles left that is 10 millimoles because 10 reacts with 10 so 20 minus and 10 is left right and 10 millimoles of this is formed right so whenever you have mixture of this CS3 COOH and CS3 COONA present then the solution is what solution is an acidic buffer solution acidic buffer this gives you the pH will be equals to pKa plus log of concentration of salt by concentration of acid pKa value from this you can calculate that will be 5 minus log 2 which is around 4.7 or 6 9 you can say right pKa is equals to like pH pH will write minus log of k is the formula pKa is equals to minus log of k that formula we can using here so it is 4.7 plus log of 10 by 10 is equals to 1 which is 0 answer will be 4.7 okay so this is the first case now this is easy this is a direct formula best question now the second case you see when we have added 50 millimoles 50 ml of 0.1 molar HCl second question you see 50 ml and 0.1 molar how many millimoles millimoles of HCl that will be 15 to 0.1 that is 5 millimoles of this so these this is the acid that you are adding right so since the solution is a buffer solution and in that you are adding this acid so that will try to minimize the change in pH right so what happens when you add this HCl into this the salt you have that is CS3 COO Na right it dissociates like CS3 COO minus and Na plus right and the acid that you have that is CS3 COOH it gives you CS3 COO minus plus H plus so what happens in this now you see how this buffer solution works when you add this is the iron we have because this is the salt of this the solution of this only we have buffer solution salt and weak acid and the salt right all these ions are present right so when you add HCl into this which gives H plus so this H plus combines with this CS3 COO minus this H plus is coming from HCl that's still that you are adding it combines from to this CS3 COO minus and this reaction goes backward and forms weakly dissociated or weakly ionized CS3 COOH and that is how it maintains the pH because you see it try to understand here you try to understand we are adding HCl we are giving H plus actually if this H plus will not neutralize then the pH of the solution will change but that nature buffer solution is what it minimizes the change in pH and how it minimize the extra H plus that you are getting from this acid that has to neutralize and that is neutralized by this reaction to the H plus combines with the CS3 COO minus and converts into weakly ionized or feebly ionized CS3 COOH and that is how the pH of the solution is maintained the whatever H plus is coming from acid that combines with this now what happens with this first of all 5 millimoles of H plus we have right 5 millimoles of this gives 5 millimoles of H plus same millimoles now 5 millimoles of this combines with 5 millimoles of CS3 COO minus right so in the reaction the concentration of salt that is CS3 COO minus decreases this is salt why because we assume that this ion combines with H plus and forms CS3 COOH right and the concentration of acid which is CS3 COOH it increases because this reaction goes in backward direction forms CS3 COOH number of millimoles of CS3 COOH was 10 initially and for this also it is 10 right so this gives you 10 moles of this and 10 millimoles of this now 5 millimoles of H plus combines with this forms 5 millimoles excuse me 5 millimoles of CS3 COOH so number of millimoles of CS3 COOH will be what when you add HCl 10 was initially present and 5 forms by this reaction with HCl this gives you 50 millimoles of CS3 COOH 15 COOH millimoles of CS3 COOH now the concentration of the salt will decrease so initially it was 10 and 5 reacts so it gives 5 millimoles of this is it clear tell me is it clear will calculate what is the answer is it clear or not you tell me so the point is what when you add HCl see actually one question that you can ask me over here that I was expecting but anyways you see here when I said the salt concentration is decreasing why not acid concentration is decreasing why not why this reaction is going backward why not this reaction is going backward see what I said H plus that you are coming here this H plus may react with this also and goes the session backward no see the first reaction won't go backward because this is a salt right it is weak it is it will be ionized easily it exists in the forms of this ion only because this is not the stable form in the solution it exists as this only but CS3 COOH is what it is weakly ionized right and this is what this has common ion effect also in these two equilibrium correct because of common ion effect CS3 COOH will suppress that association of this so what we assume in this mixture this NIN is mainly because of that association of this salt not because of this acid right what we say that this acid is weakly ionized so concentration of CS3 COOH minus in the solution is mainly because of dissociation of salt not because of acid so when this H plus combines then we say okay mainly because of this salt only when this H plus combines then the salt concentration will decrease because it combines with H plus and converts into weakly ionized CS3 COOH and that's why we are saying that salt concentration will decrease and acid concentration will increase salt concentration will decrease and acid concentration will increase right now you see this is the concentration of salt we have and this is the concentration of acid when we add these many moles of HCl into it now we can use the formula of pH which is again pH is equals to pKa plus log of concentration of salt divided by concentration of acid that gives you pKa is 4.7 plus log of salt by acid is log of 5 by 15 which is 1 by 3 so 4.7 minus log 3 this gives you the pH of the solution when you solve this you'll get pH of the solution log 0.3 is 0.47 or 0.48 so 4.7 minus 0.48 gives you the answer over here 4.2 something you'll get probably did you understand this did you do the same thing now that's third portion of this question is what when we add question c we add 0.150 ml of 0.1 mol of NaOH 50 ml of 0.1 mol of NaOH what is the millimole of this again it is 5 millimoles right again it is 5 millimoles now in this again you see the equilibrium exists between these two reactions which is the acid CS3 COOH it dissociates like CS3 COO minus and H plus and another one that is salt CS3 COO Na CS3 COO minus plus Na plus okay now in this solution in this solution we are adding NaOH sorry we are adding NaOH into it here NaOH we are adding so NaOH actually combines with this this OH minus that you are giving because this is base we are adding so we are giving OH minus into this so mainly dissociation of this only this is weakly ionized dissociation of this will be very less because of again common ion effect here you see common ion effect so main the concentration of Na plus will be far more than that of H plus so this OH minus combines with Na plus over here right and forms what Na plus plus OH minus and it gives NaOH in the reaction vessel right so obviously when this is combining with this so this reaction is going when you add base into it the second reaction is going into forward direction when you add acid into it the first reaction is going into backward direction that is how it neutralize the additional OH minus or H plus that we are giving in right so this is the extra OH minus we are giving in it has to neutralize to maintain the pH since it is a buffer solution right and it is neutralized by this NaOH Na plus and OH minus now when this reaction goes into forward direction obviously the concentration of CS3COO minus in the solution will increase and how it increases 5 millimoles of this combines 5 millimoles of this so extra 5 millimoles of this CS3COO minus forms so that will be again 10 plus 5 here 15 millimoles of CS3COO minus will get and and what about acid right acid concentration will decrease right so that CS3COOH will then forms 10 minus 5 is equals to 5 millimoles here so salt concentration is increasing acid concentration is decreasing so pH of the solution that will be pKa plus log of salt by acid salt is 15 acid is 5 so 4.7 plus log 3 that will be your answer here 4.7 plus 0.47 or 48 whatever you take that is the answer we will get here understood okay so you try to think on this question again at home okay this is a very good question which actually helps you to understand the question how buffer solution works okay but again if we take the class we'll take the revision class of this we'll discuss this again the working of buffer solution okay now there are some facts that you must keep in mind that for effective buffer the ratio of salt by acid should be in this this one you write down salt by acid should lie in this range for effective buffer solution okay and with this if you put you'll get the range of pKa you can find out this with the formula pKa minus 1 less than equal to pH pKa plus 1 this question they have asked many times in the exam for effective buffer the pH range should be this you can put this and this value into pH formula you'll get this one more thing here you see the log of salt by acid concentration that you have or in case of basic buffer salt by base okay this this particular portion this log part in the formula this gives you the change in pH delta pH so if they ask you what is the change in pH you have to find out effective buffer solution means what an engine that uh see we must have the ratio of the salt of concentration and acid for a solution to behave as a buffer solution like all other solutions are not buffer solution for that we should have a definite range of salt and acid concentration of salt and acid right so that ratio we must have so for effective buffer solution means for a solutions to behave for a solution to behave as a buffer solution the salt by acid ratio is found to be in this range minimum is 0.1 and maximum is 10 okay so this point this term sometimes they ask this question also and when you put this ratio 0.1 and 10 into this particular formula you'll get the range of pH on the basis of this we'll get this pH this is actually the experimental value we have okay 0.1 to 10 that's the thing right so but this this thing you keep in mind sometimes they ask you this thing directly and how do we get this formula we have here right salt by acid is nothing but this portion first you put 0.1 here and then you put 10 here you'll get pk minus 1 and then pk plus 1 the pH value understood okay naturally we'll see some concepts of general organic chemistry and we'll try to understand the concept with help of the questions okay questions itself we'll see okay we'll see now geoc see in geoc like again we cannot discuss all other things so we'll directly discuss the various electronic effects okay in organic chemistry that is various electronic effects the various electronic effects are first one we have inductive effect the first effect is inductive effect second one is mesomeric effect mesomeric effect and this also will discuss one concept of resonance also hyper conjugation just a second okay so hyper conjugation electromagnetic effect electromagnetic effect so first question that they ask from this that the first three effect that we see that I have written here these are the permanent effect okay this is permanent effect and this is temporary effect permanent and temporary effect okay so what do you understand by this electronic effect suppose I have take one I have suppose if I take one molecule like c c c c and x halogen electronic effect is nothing but the displacement of electrons displacement of electrons how electron like you know displaced from one point to other point okay that's the meaning we have here electronic effects okay now like I take this example okay obviously this halogen atom attached with this carbon right that is more electronegative than the other than the carbon atom that is present okay halogen atom present over here it is more electronegative so what happened the bond pair that you have here it is slightly shifted towards this halogen atom and then it becomes del negative it will have slightly negative charge and this carbon will have slightly positive charge now when this is positive charge we have so this will also drag this electron pair to this side this becomes del 2 plus positive charge on to this and like this this positive charges is what is keep on decreasing as we go away from this x right here we will have maximum density of positive charge here we have lesser here we are even lesser and like this the positive charge density decreases and now when this positive charge density decreases with the density to withdraw electron or attract this bond pair of electron towards its side is less right and we say that this kind of effect we call it as i effect inductive effect inductive effect and why it is permanent because the molecule is halide only right it is alkyl halide and it is a molecule whenever this x is attached with this carbon this things this thing we can observe easily right that's why it is a permanent effect now the two three points that you have here you have to keep in mind that it involves only it involves only sigma electron it involves only sigma electron right now and it is what it is distance dependent also distance dependent and it is found to be the effect of this is found to be negligible after second or third carbon mainly third carbon or second carbon also sometimes we say so after second or third carbon the positive density is almost zero and then we don't observe any kind of displacement in the electron right so only sigma electrons are involved it is distance dependent also these things has been asked in the exam also right which of these are distance dependent effect like this they have asked the question okay so again you have to understand this and keep this in mind an important point it is but this thing is not true when we have resonance okay resonance we have or inductive or you know this mesomeric effect in mesomeric effect these is not true because there is pi electrons involved right there's pi electrons involved and that is not distance dependent also for that conjugation is required okay if conjugation is not there then no displacement of electron in mesomeric effect okay so there are two three characteristics of this inductive effect we have this is first thing permanent effect I have written over here sigma electrons involves okay transmission and distance dependent effect transmitted along transmitted along carbon chain right and it is represented by this arrow means the electron is displacing from this side to this side okay so if you see this one two three four and five if I write so this is chlorine right so chlorine will drag electron towards this side this also drag electron this also drag electron and like this it goes right so it is del plus delta one plus delta two plus like this so positive r density continuously decreases here right so this is the characteristics of sigma or what we say eye effect now this eye effect like I said this is the group that can withdraw electron from the carbon chain halide ions are the group or the halogen atoms are the group which can withdraw electron from the carbon chain right so this kind of group with withdraw electron from the carbon chain we call it as minus eye effect basically eye effect classified into two categories right one is plus eye and other one is minus eye minus eye group are those group which can withdraw electron or drag electron withdraw electrons plus eye are those group with releases electron releases electron so in this thing first of all you have to keep this in mind that which molecules or which atoms shows plus eye nature or which atom shows minus eye nature okay that you have to keep in mind since you see minus eye groups are the group which withdraw electron correct so they they must be electron deficient or positive charges species right so some examples I write down here that you copy down and you have to keep this in mind examples of plus eye and minus eye right so first of all you see examples of minus eye minus eye group maximum minus eye is for this nf3 plus then we have nr3 plus nh3 plus no 2 c triple bond n s o 3 h c o o h minus fluorine then chlorine then bromine iodine right c o o r o r o h then we have alkyne phenyl right these are the few examples we have actually we also take the reference of carbon and hydrogen right all those groups which has more tendency to withdraw electron then the carbon and hydrogen bond those are said to be minus eye all those groups which has more tendency to release electron then the carbon and hydrogen bond are said to be plus eye okay see this is the order that is given in any other book actually okay but if you can memorize this it is fine okay but I will also suggest to you to you know to use some logic you know common sense so that you can compare which one will have more plus eye or minus eye because these groups eventually affects the acidity and best city nature of any compound right and that is what the application part we have that we'll see okay so first of all you should know which minus eye group is dominant over which minus eye group then also you then only you can say okay this is more acidic or less acidic okay so few you know few common sense or few logic you can apply to understand okay first of all if electronegativity is more as electronegativity increases tendency to withdraw electron increases minus eye effect increases we can say this as electronegativity increases minus eye nature will be more for example you see the first one if I compare fluorine then chlorine then bromine and then iodine right obviously fluorine has maximum electronegativity order of minus eye should be this correct and that is what the order given here also okay second one you see if I ask you to compare the electronegativity of OH and SH which one will be more if I ask you to compare the electronegativity of NH2 and pH2 NH2 and pH2 fourth one suppose if I give you NH3 plus and NH2 OH2 plus and OH tell me OH and SH which one will have more minus eye okay so first one the order should be this because oxygen is more electronegative than sulfur the second one order is this nitrogen is more electronegative than phosphorus nitrogen is more electronegative than okay we have nitrogen only over here but this is the positive charge so it has more tendency to withdraw electron more minus eye oxygen positive charge more minus eye fluorine oxygen and nitrogen fluorine is most electronegative the order should be this right if you compare this one CF3, CCL3, CBR3 and CI3 the order of electronegativity should be a minus eye should be this this is the order okay so like this you can actually compare the minus eye nature of the group okay so you don't have to memorize this okay if you keep this in mind you can do many other questions okay we'll see the application of this also but we'll see we'll see few examples of plus eye okay plus eye group you see plus eye group plus eye group means what electron releasing electron releasing means what it has it must have electron present so either it has lone pair or negative charge on it okay that is the logic you can keep in mind suppose I have the first one which is CH2 lone pair, lone pair negative charge it is maximum then we have NH two lone pair negative charge oxygen lone pair negative charge C okay all alkyl group alkyl groups electron releasing so if I compare this CH3 CH3 then C CH3 H H C CH3 H CH3 and the last one we have CH3 whole thrice C what is the order of plus eye for this the plus eye will be maximum for plus eye will be maximum for this group because it contains three methyl group you see if you compare these two this has electron releasing tendency this has also electron releasing tendency this has electron releasing tendency right so here we have two electron releasing groups similarly here we have three electron releasing so maximum for this then we have this one and we have this in the last we have this yeah so this is correct right one more thing you see for if you if you have isotopes right suppose we have CT3 tritium and then deuterium right so CT3 will have maximum then we have CD3 and then we have CS3 this is also important okay for isotopes you must keep in mind bond length if they ask you bond length of carbon hydrogen bond is more than the carbon deuterium bond and is more than the carbon tritium bond so carbon tritium bond side bond bond length increases tendency to lose electron decreases okay that's the thing okay now few examples that we have already seen now we directly move to this you know some application part of it okay so eye effect eye effect also helps in you know determining the stability of intermediates like carbocation carbanion and then the acidic basic properties okay so we'll see first the stability of intermediate first question first type of question we'll see and then we'll see the acidic and basic nature okay so from 11th class who are there niranjan you're there niranjan there thus shushant is there no i don't think so anyways so we'll see this okay a few examples i'm giving okay so goc is the best way to understand goc is to solve questions okay there is theory that i have told you already okay most more application part you will see more you will understand okay so first one you see suppose if i uh take this example here we have positive sign carbocation okay one more thing is this positive charge this is fluorine and this is also fluorine first question is this we have to find out the stability of this carbocation positive charge carbon means carbocation find out the stability of this right positive charge here here we have positive charge this is methyl these two are methyl group here we have ch2 positive and then we have three positive and here we have ch2 positive here we have ch3 these two okay the first one see all like one thing you try to understand in organic chemistry if you have any charge species right so charge species is always less stable less stable than the neutral one always less stable than the neutral one okay so if you have any charge species if you are if you are able to neutralize the charge then the stability you are getting right so all these charge species you see right if it is neutralizing by these groups right and that is only possible when it releases electron right so what we can write down stability of carbocation stability of carbocation is directly proportional to directly proportional to plus i group and inversely proportional to minus i group okay that we can write minus i means what it withdraw withdraws electron right when suppose you have any positive charge right and when it withdraws electron then positive charge density will increase right suppose if I take this example one example I'll take here that is ch ch2 positive and here we have fluorine right another one we have ch2 positive and here we have oh ch3 just a second right these two examples I am taking right and one more example suppose if I write this okay this one you let me we'll discuss later ch two positive and ch3 this is the three examples I'm taking okay so stability of carbocation you see both are positives first of all you compare these two it will be you know easy for you to understand okay especially for those 11 plus students okay so you see this f has minus i nature right so it withdraws electron and when it withdraws electron the positive charge density on this carbon increases right this cs3 has tendency to lose electron so it releases electron so electron is going on to this carbon so positive charge density here decreases right so whenever we have increase in positive dense charge the stability will be less because we have to neutralize the charge species then only the stability will be more so if positive charge is there then electron you have to push to gain more stability if negative charge is there the electron you have to withdraw right and that's what we are saying carbocation means positive charge carbon directly proportional to plus i and inversely proportional to minus i if you take this one right this one and this one if you compare this oxygen has tendency to withdraw electron right so that will increase the positive charge density here but this tendency is less than this right so stability of this is more than this cs2 fvm so if you compare the stability of all these this is the first maximum stable then the second is this and third is this stability of this okay now only with this logic we'll try to solve this these examples that i have given you okay so now you see the first one the first one these are methyl electron releasing group right electron releasing and these are fluorine so electron withdrawing group electron withdrawing positive density here increases so stability will be less order will be this here you see oxygen has electron withdrawing nature and this methyl has electron releasing nature right so stability of this will be more because the positive charge will more linearize here cs3 electron releasing nature and f3 electron withdrawing nature stability of first is more than second this is three degree carbocation this is two degree carbocation and this is one degree carbocation three degree carbocation is most stable then two degree then one degree why because it has three alkyl group two degrees electron it has only two alkyl group and this has only one alkyl group so this is the order of i effect that we have order of stability of carbocation according to i effect o cs3 is more stable than f happen critique see o cs3 and f uh minus i nature if you see first of all the order that i've given you in that you see f has more minus i nature than o cs3 and if you know the order it's fine otherwise you can you know you can logically you can understand this fluorine is withdrawing electron oxygen is also withdrawing electron but this methyl has tendency to release electron right because of this electron releasing tendency that tendency to withdraw electron of oxygen will decrease here first case second case anyways if you if you compare fluorine and oxygen fluorine is more electronegated so that will withdraw more electron oh yeah correct critique then yeah right right so these are the few examples of stability of intermediate right like carbocation and all fine now in this if you see the stability of uh or the acid acidic and basic uh nature right acidic strength and basic strength we see some more examples we'll see into this for carbon ion okay just reverse of this carbon ion and then we'll see acidic and basic strength here we can extend this class up to uh 12 15 right do you have any other class after this can we extend this class up to 12 15 okay okay so we'll take this class then till 12 15 okay you see this uh tell me the stability order of all these first one negative charge negative charge first one is this second one is this chlorine negative charge we have here cs3 cd3 and ct3 isotopes of hydrogen tell me the answer in all this yes the first one the first one you see it is the carbon ion right negative charge we have so in this what we can apply the logic that stability of carbon ion just reverse of that carbocation carbon ion is directly proportional to directly proportional to minus i group and inversely proportional to plus i group right directly proportional to minus i inversely proportional to plus i right so here you see this is three degree carbon ion this is two degree carbon ion and this is one degree carbon ion it has three electron releasing group so stability of this will be least then we have second and then we have first in these two you see in this with the chlorine is closer to the chlorine the compound that you have over here and this chlorine has minus i nature so the electron density here will increase more than here so obviously the stability of second one is more than to that of first one oh sorry it is in the reverse order no this is a drawing correct the stability will be this okay first is more than second now you see n o2 and nf3 both has minus i nature n o2 and nf3 both has minus i nature but since we have oxygen here and we are floating here so which one will have more minus i floating right so minus i of nf3 is more than to minus i of n o2 and one positive charge also we have here this will withdraw more electron so obviously the stability of second is more than to that of first right ch3 cd3 ct3 this has maximum plus i right cs3 shows plus i effect no so both all these three will show plus i but plus i of ct3 is maximum i told you this plus i is electron releasing electron releasing so stability is minimum for this maximum for cs3 order will be this okay now next the last thing that we'll discuss today that is acid base strength acid base strength see in organic chemistry we'll consider the acidic strength it is cd3 not co3 i said it is cd3 so shouldn't the last one be opposite okay let me check last one you see what is the question that is isotopes of hydrogen right this is ch3 has plus i nature and the plus i nature of for ct3 is maximum understand swetha plus i nature of ct3 see the plus i nature of ct3 is maximum right ct3 has maximum tendency to lose electron tendency to lose electrons right this is cd3 i told you this ct3 the plus i nature of ct3 is more than to the plus i nature of cd3 and that of ch3 so more will be the plus i more will be the electron density here and less will be the stability you see stability is inversely proportional to the plus i effect that's why the third one is the least stable yeah because there is negative charge on the top and plus i nature will decrease the stability okay now you see the acid base strength you see in organic chemistry like i said the acidic strength we define by the tendency to lose h plus i and however we have two three more you know definitions of acid tendency to in with respect to the lone pair and all but in organic chemistry acids are those compound which loses h plus i and h plus iron in water h2 with respect to water we take with respect to water okay and any compound right suppose r h or any other compound right any compound if it loses h plus iron the iron that we get after losing h plus that we call it as the conjugate base okay and the strength of strength of an acid depends upon depends upon the stability of stability of conjugate base right stability of conjugate base so suppose if i take this r c o o h r c o h okay or suppose if i take this here c h 3 c o h okay c s 3 c o h and suppose we have c 2 h 5 c o o h now this is the acid and we have to compare the acid strength of this so what we'll do we'll just form the conjugate base of this minus h plus so when it loses h plus what it forms it forms c s 3 c o o minus and when this loses h plus it forms minus h plus it forms c 2 h 5 c double bond o and o minus correct now this is the conjugate base of this acid this is the conjugate base of this acid any acid you have right suppose we have h 2 o when it loses h plus it forms what o h minus and h plus so o h minus is the conjugate base of h 2 o if you have h cl so its conjugate base is cl minus we have h s of 4 minus its conjugate base is s of 4 2 minus just you release or just you remove h plus from that compound okay and now when this conjugate base is more stable it means for this molecule the tendency to lose h plus ion will be more because on losing h plus ion it is forming more stable conjugate base correct that is true for this compound also so if the conjugate base is more stable the tendency to lose h plus ion will be more and hence the acidity will be more okay c s 3 c o i am coming back to this Pratik so you see if you check the stability of these two conjugate base okay so that again depends upon the plus i nature of what plus i nature of c s 3 and c 2 h 5 so this is the both shows what both shows plus i effect this is also plus i and this is also plus i and because of plus i we know the the stability of an ion decreases this is a negative charge an ion so because of plus i the stability decreases but which which one will show more plus i c 2 h 5 larger group c 2 h 5 shows more plus i effect so that's why the stability of this compound is lesser than the this compound and hence the acidic order is this c s 3 c o h is more stable than c 2 h 5 so one more thing you can write here acidic strength is directly proportional to minus i effect and inversely proportional to plus i effect that is the same order of an ion strength yeah yeah it's relative it's relative Pratik this acidic and basic thing is obviously it is relative right basic thing if you have to compare because you compare acidity and then reverse of that will be the basic order okay that is a simple thing few examples we'll see then probably you understand yeah right c 2 h 5 is even more weaker okay that's why it is so yeah there's this acid and base thing everywhere it is relative only right you see if you take if you take h 2 s of 4 right if you take h 2 s of 4 water generally we don't see that we don't see the what acidic nature of water h 2 all right we don't see that as as nature of water but if you compare NaOH and h 2 obviously h 2 is more acidic than NaOH because NaOH is the base you understand this so acidic and basic strength is always is always relative right in any equilibrium only you have started at c l of 4 is the most most acidic compound we have see that if you see a little bit of example if i'll give you hc l of 4 is most the acidic strength of hc l of 4 is maximum okay and then we have suppose hi we have hbr we have right h 2 s of 4 also we have up to this and then we have hcl like this the strength is there so if you compare hi and hbr so obviously hi is more acidic than hbr but if you compare hbr and h2 s of 4 hbr is more acidic than h2 s of 4 and then it is true for hcl and h2 s of 4 also right so it is always relative okay few examples you see one very common type of question that they ask many times that is hf hcl hbr and hi second roh rsh h2 s and hcl rc triple bond ch rch double bond ch2 rch2 ch3 hcn hch double bond nh it is acidity order acidity order you have to find out okay now you listen to me all of you see one thing for this acidic and basic strength generally you'll get two types of questions okay in one type there will be variation in size okay what i said two types of question you'll get in first type there will be variation in size variation in size and what i what we say that the acidity is directly proportional to the size of an ion because large size more uniform distribution will be there of the negative charge and that's why the stability will be more okay large size more uniform distribution of negative charge and stability will be more okay and then in the second type we have the size is not that much varying but electronegativity is there right electronegativity sizes is not that the difference in size is not that much but electronegativity difference is there so in that case acidity is directly proportional to electronegativity now you see these three questions one two and three in this there is size in there is a variation in size fluorine chlorine bromine iodine oxygen sulfur oxygen and sulfur right there is a variation in size in this you see sulfur and chlorine belongs to third period only there is not much variation but yes electronegativity difference is there right here we have carbon and carbon electronegativity difference here you see this carbon is what this carbon is sp hybridized this carbon is sp2 hybridized and this carbon is sp3 hybridized difference in electronegativity this carbon is what sp hybridized and this carbon is sp2 hybridized carbon carbon atom size is same but difference in electronegativity is there if the conjugate base is stable vashnavi you think one thing yeah how do you get conjugate base by removing h plus so if after removing h plus if you are gaining stability it means you will happily lose h plus no so that's the thing over here conjugate base we get after losing h plus so if conjugate base is stable it means the tendency to lose h plus ion will be more and that's why it is a stable more acidic compound it is more stable conjugate base more will be the acidity of that compound this is the one thumb rule you should keep in mind understood another thing you see like i said variation in size and electronegativity these two factors you have to keep in mind then you can put some logic why is the size of an ion is directly proportional to this acidity because more will be the size since the size is this negative charge and the size is this negative charge okay more will be the size more will be the distribution uniform distribution of this negative charge over this anion and that's why the stability will be more more uniform distribution means what more stability right so now you see here h f h c l h b r h i what is the conjugate base of h f f minus c l minus this is br minus and this is i minus so which which has the maximum size obviously iodine has the maximum size right so obviously the stability of iodine is maximum over here right so that's why the order of acidity is this is it clear one more thing you can think over here the bond between this h f is what it is one s and two p bond one s two p this is one s three p one s four p and one s five p okay bond length is maximum over here as bond length increases bond strength decreases right and bond strength when decreases tendency to lose h plus will be more that is also one of the way that you can think h i is most simple oxygen and sulfur you see if you lose h plus you'll get o minus and s minus so since s minus sulfur psi or sulfur is more than to that of oxygen that's why the stability of conjugate base for this compound will be more and acidity of this is more yeah predict like that also you can think oxygen being more electronegative draws more electrons and then the electron density on oxygen is more that will destabilize that iron see whenever we have the contradiction in size and charge we always give preference to charge that we always keep in mind yeah more negative see whether it is more negative charge or positive charge whenever the charge is more it is always less stable neutrally species is always more stable than the charges species so whenever you have tendency to decrease the charge you are going towards more stable state right if we have contradiction in size and electronegativity or charge we always prefer charge as a major part here right charge will always as a major factor okay so now you see the first three that I have given you it is based on the size factor oxygen sulfur both will have negative charge in its conjugate base but sulfur having more size that's why the stability of this compound is more and hence the acidity of this is more oxygen sulfur again you see both will have negative charge in its conjugate base sulfur having more size stability of this is more and hence acidity or it is this what is the confusion tell me see you listen to me one thing just one thing you listen to me there are two types of question one is when there is difference in size like the first three are given you and other one then there is difference in electronegativity no no no wait listen to me one is size difference and electronegativity difference so you don't consider this size and electronegativity see I am again explaining this okay you just listen to me don't think anything else I'll explain everything when you have both factors and what you have to keep in mind just you listen to me first first of all two types of questions are possible variation in size variation in electronegativity correct when size variation is there right so as the size of anion increases acidity increases this is the thing I have written it over here you see acidity is directly proportional to the size of anion this thing why it is actually proportional because more will be the size more uniform distribution of the charge will be there and hence the stability will be there so when you form the conjugate base of these compounds as the size of anion increases distribution of charge will be more uniform that leads towards the stability or to that the conjugate base wait wait wait wait let me explain correct so now coming back to this size factor first example you understood f minus cl minus br minus i minus i minus maximum size so most stable conjugate base and that's why the acidity order is this coming back to the second one you'll get o minus here and s minus here right so both will have negative charge size of sulphur is more so this negative charge here is more stable so acidity of this compound is more and same logic we have applied here right now if you have now if you have any contradiction if you have any contradiction in size and charge then we always prefer this charge factor into this size will not be the major factor right so for s h if you consider size or electronegativity s h is no you see Pratik like we cannot here you see here if you compare these two compounds oxygen and sulphur right so we have difference in size we have oxygen present here see I know where you have got confused you are you must have things have I don't we take electronegativity of this oxygen and electronegativity of the sulphur right that will not take when we take electronegativity here you see this kind of compound you see sulphur and chlorine both belongs to the third period right after sulphur we have chlorine right so obviously there is not much size difference here but electronegativity difference is there if you see we'll also have the size difference here so this you have to think right second example you see this carbon and this carbon do we have electronegativity difference here yes we have but do we have size difference no so we'll we'll take electronegativity here but here what we have when the elements belongs to different group or sorry different period right this is for this is for second period oxygen and this is for third period sulphur so when there is different period we have then we'll take the size factor here you see it is it is clearly understood that size is same we'll take the electronegativity factor carbon and carbon size is same we'll take the electronegativity factor right sulphur and chlorine size is very much same right very close but electronegativity difference is there right in all this example you see I have given the term which belongs to the different period when we have different period you consider you consider size in that case chlorine chlorine bromine iodine different period did you understand yeah it may be yeah Pratik correct it may be uh in some examples it may be it may be that it it won't make any difference but actual thing is this only if if you have any contradiction in size and suppose in one example in one example I have given the variation in size also and variation is electronegativity also I've given you three four examples three four molecules like that in that case we'll go with charge factor not the size factor okay so the point here is what all these things according to the size I have given you this thing the stability of what suppose this is this forms what cl minus conjugate base and s2 minus conjugate base right so chlorine is more electronegative negative charge on more electronegative is always more stable so obviously the hcl is more acidic than h2s which is more electronegative here sp hybridization is more electronegative so this is more most acidic than the second one and then the third one in these two again sp this is more electronegative is it clear now tell me okay so hello it's 12 30 now okay I'm getting late okay we'll we'll continue with some more example in the next revision classes okay fourth one which is the fourth one h2s and hcl okay h2s and hcl you see chlorine is more electronegative obviously right and we have to consider the electronegativity factor so acidity you see acidity is directly proportional to the electronegativity here you see acidity directly proportional to the electronegativity why more negative charge you always keep in one thing one thing in mind negative charge on more electronegative element negative charge on more electronegative element is always more stable is always more stable reverse of this is also true positive charge on more electro positive element is always more stable yeah chlorine is more is electronegative than sulfur that's why okay so negative charge and more electronegative positive charge on more electropositive elements are always more stable okay these two things you should keep in mind okay is it clear now if you take here H2O also if you take here H2O then this is the most acidic that's why you see it is again you see the relative thing yeah yeah right Pratik correct I know where you got confused again you are mixing these questions question number two and question number four right Pratik question number two and question number four you are mixing right okay hello Pratik we'll discuss this next class okay I know Pratik where you got confused but I'll tell you see actually depending on the question you have to think that what logic you should apply it is a bit confusing I can understand okay but then again I'll discuss this next class okay you have another class at one o'clock so I won't take much time okay yeah yeah yeah we'll discuss this next class okay Pratik I understood where you got confused but that is also I have explained but again I'll explain again okay don't worry so no bye bye take care okay we'll discuss some more examples in the next revision classes okay so bye bye take care thank you