 Yeah, good evening guys. Can you hear me? Yeah, so last class we started with the hydrogen and we were doing the preparation of hydrogen, correct? the first Yeah, the first method that we have done is By the action of water on active metals Okay, we'll continue with this chapter hydrogen today. We'll finish it off and then we'll start with s-block. That is group one Okay, so we have seen that active Yeah, I got it. Okay. See actually, yeah, see actually what happens the That report no advance assignment that report is systems generated Okay, if you have not submitted on time and if it is some submission is done from our side, then your name won't be there Okay, we can't do anything into it. So those who have shared with me your assignment Personally like we have the database. Don't worry. Okay The thing is the report that we generate it is system generated. Okay, we can't change it So for this time you let it be as it is next time onwards. You submit it on time. Okay, like suppose It's 10th is the date by 10th morning. You must submit better at 9th evening You'll submit but I'll try to submit on my side or the assignment on 10th evening or by night Okay, so you have that 10th proper like the entire day you have with you Understood kind of yes So we have done with the first like you know method that is amalgamated metal We use in order to reduce the rate of the reaction so that The you know chance of catching fire will be less Okay, that is what happened the first method when the you know when the reaction proceeds It is highly exothermic reaction huge amount of energy releases Right in order to reduce that we use am I we use amalgamated metal? Okay, now the second method of preparation all of you write down the second method we have By using by using alkali solution by using alkali solution write on metals like betelium Zinc tin Aluminium etc reacts with reacts with boiling alkali solution boiling alkali solution and Liberates hydrogen. Okay reaction you see beryllium with NaOH to NaOH When you heat this It forms and a to be or to an H2 releases This compound we call it as sodium beryllate similarly if you have zinc Reacts with NaOH to NaOH gives Na2 ZnO2 That is sodium zincate and hydrogen gas releases sodium Zincate okay, these are the reaction we have for the preparation of Hydrogen with alkali solution copy this down you go to the next next time Type of metals as in what can we say these are active metals we can say Transition metal also zinc is a transition metal. Okay magnesium very sorry beryllium is an active metals Aluminium's The metallic properties lesser if you compare with all other elements So these you know metals have different different behavior But one property is common. They have tendency to release electrons next write down the third method of preparation by action of of dilute acids on Certain metal dilute acid on certain metal right on metals which are more electro positive metals which are more electro positive then hydrogen atom reacts with reacts with dilute acids and Evolve hydrogen evolve hydrogen for example, you see We have zinc Zinc react with S2 SO4 dilute acid Can say that yes displaces hydrogen It is Zn SO4 plus H2 gas releases a right displacement reaction on certain similarly if you take fe with HCl dilute Gives FeCl2 plus H2 one question that they ask in this here If you take copper copper plus H2 SO4 dilute and if you write CuSO4 Plus H2 this reaction is not possible It does not release hydrogen because Copper is not more electro positive than hydrogen. It cannot displace hydrogen from its from dilute acid the reason for this to is why zinc can displace why not copper is The reduction potential Okay For example, if you see if I write down the reduction potential of copper copper when converts from Cu2 plus to Cu its reduction potential is 0.34 volt The reduction potential of zinc is Zn 2 plus to Zn is minus 0.76 volt and the reduction potential of water Plus to H2 this is 0 right, so those Metals which has lesser reduction potential than hydrogen are more electro positive and can displace Hydrogen from dilute acid Okay, so you also form we have different methods of preparation. There is not only one method Nishant, right? There are other methods also by which we can prepare copper sulphate if you want you can write it down this reduction potential Will study this particular thing in 12th state 12th grade where we have electro chemistry Yeah, so these values will see how do we get it? It's a relative reduction potential with respect to hydrogen if you want you can write it down But this information you must keep in mind that zinc can displace copper cannot displace hydrogen Because the reduction potential of copper is more than to that of hydrogen. That's the reason, okay? Right, so this is the three methods of preparation. We have these are not commercial methods, okay? See for the preparation of any element or compound We have various different methods Commercial methods are those which we use in an industry in order to obtain large amount of the product correct Since we are using an industry, so there are various factors like for example, you know the cost Input should be less. Okay, easy to handle, right? You know Waste is also very less should also be less. Okay, so those kind of criteria is there in industry Miss the basic principle is yes, we want to give minimum input and maximum output Right so that we can make profit so in industry We use only those methods which are easy to handle cost effective plus we'll get large amount of product with minimum input, right? so The commercial method of preparation we have again two three methods The important one we are going to discuss the first commercial method of preparation we have that is electrolysis of water Right, so write down the heading commercial Preparation method or commercial method of preparation method of preparation means on a large scale. How do we prepare it? correct, so In this the first, you know method we have that is Electrolysis of water, you know what is electrolysis? electrolysis of water Yes, so any electrolysis what happens? Let me draw the diagram first and then we'll explain you all of you draw this diagram This is the two electrode we have and here we have inlet of water and in this, you know container we have Electrolyte present which goes under electrolysis Okay, this is water with 20% of NaOH pure water is bad conductor of electricity to make it good conductor. We add We add NaOH into it, right? We add NaOH into it, right? We can also add S2, SO4 for this purpose Okay, now through this electrode We allow this Current to pass through it So we add an external source of current that is a battery we add To this electrode of certain bolt. Okay The moment you connect with it current passes through it This is a positive end of the battery. This is a negative end of the battery This rod also becomes negative because it is connected to the negative end This rod becomes positive because disconnected with the positive end Positive rod in electrolysis we call it as what anode or cathode? Positive rod is anode Can anode be negative also? negative anode possible? No, is it? We have two types of cell Correct. One is electrolytic cell other one is electrochemical cell So in electrolytic cell anode is negative over there that you will again study in electrochemistry So it's not like it's not like anode is always positive Anode is positive in electrolytic cell Electrolytic cell are those cells in which electrolysis takes place to obtain current Correct. So in electrochemical cell anode is negative. Let it be it's not required here Okay, and here we have an output like we have an Outlet here through which the gas can you know come out through this we have an outlet like this Okay, so now you see in this, you know In this mixture the electrolyte that we are taking we have ions present here, right? What all ions are there where any plus OH minus and H plus there the ions present ions that we have here It is OH minus any plus H plus all these ions we have here when the rod becomes negatively charged here So automatically what happens all these positive charge ions will attract it towards the negative electrode that is cathode and The negative charge ions attract towards the positive electrode that is anode Okay, so at anode we know whether it is negatively charged or positively charged at anode We always have oxidation Always oxidation and cathode we always have reduction So this OH minus moves towards this anode and at anode the reduction takes place Okay, so the reaction at anode is Since the OH minus we get from water. So reaction of anode is 2 H 2 O Sorry, I know do we have no Yeah Reaction at anode OH minus will go towards anode. So reaction is 2 OH minus converts into H 2 O Plus half of O2 Plus 2 electrons. This is the half reaction like we did in redox reaction. Okay The reaction at cathode if you see It's a reduction. So consumption of electron So what a molecule which gives H plus gets reduced at cathode and it converts into 2 OH minus and H 2 at cathode So what we are, you know seeing over here at anode what happens at anode oxygen evolves and At cathode hydrogen involves this question. They ask him like that. So from here H 2 gas comes out Right and from this outlet O2 gas comes out. Okay, but there are chances of you know Mixing of H2 and O2 and they provide again water molecule to prevent this mixing We also use here an asbestos diaphragm, which separates the two part action You know, it does not allow the H2 and O2 to mix together. This we call it as asbestos diaphragm The purpose of this asbestos diaphragm is to prevent the mixing of H2 and O2 This is the electrolysis of water. Copy this down. Yeah, we'll have OH minus present Like we'll have an excess. So what is the deal with that? No, it's not Because OH minus is coming from H2O and NaOH Correct. So when these two dissociates will get equal number of H plus and Na plus also Initially, right? So the neutral so that mixture will be neutral In a polite will be neutral initially When electrolysis starts Then it can be maybe may not be It depends upon how many H plus and OH minus will get Reduced and oxidized respectively based on that we can say After electrolysis, you can say if the but it depends like the number of OH minus and Na plus and H plus is present If equal number of H plus and OH minus will get neutralized will get oxidized and reduced Then we then the solution will be what solution will be Neutral only So it depends upon the ionic mobility of ions also So H plus is a little higher contains a little higher ionic mobility than OH minus Yes, you can say after electrolysis when the electrolysis is done or when it starts the electrolyte will be slightly negatively charged More number of negative ions will be there correct So this is the electrolysis of water, okay, we use your NaOH in order to make this water Conductive in nature because we know pure water is bad conductor of electricity Yes, we can also use S2SO4 here NaOH or we can also use S2SO4 Understood. Yeah use H2SO4 or use NaOH The product of electrolysis would be same it won't be different In that case also at anode oxygen evolves at cathode hydrogen evolves Okay, next slide down By Bosch process in Bosch process one thing that they ask very often is what catalyst we use in Bosch process the catalyst we use is nickel here and We use very high temperature here around 1270 Kelvin temperature we use Temperature you don't have to memorize catalyst. You must remember. Okay, and this process what happens superheated steam Superheated steam Is passed over is passed over Red hot coke. So we have the reaction here carbon solid red hot coke with water in the form of steam and It converts into CO plus H2 this is not cobalt. This is Carbon monoxide the hydrogen that we get here is impure hydrogen because the presence of carbon monoxide in this and This mixture We call it as water gas CO plus H2 important information. It is it is water gas Right. We also call it as sin gas or we also call it as Synthesis gas all are the same thing The reaction is endothermic in nature Endothermic in nature. Yes understood So since the hydrogen is impure over here and the impurity is carbon monoxide So we need to remove this impurity in order to get the pure hydrogen So to remove this impurity carbon monoxide is oxidized into CO2 Okay, just give me a second Carbon monoxide is oxidized into CO2. So how this reaction takes place this reaction co plus H2 the water gas is Further reacts with water in presence of a catalyst called ion chromate ion chromate is Fe CR04 this catalyst we use To oxidize carbon monoxide into CO2 and this CO2 then escapes into the atmosphere and will take Will have extra so catalyst for boss process is nickel. It's not ion chromate This we use to oxidize CO into CO2 and I we use in the first step here The first reaction takes place in presence of nickel then Okay Now the next method is from hydrocarbon What do you mean by hydrocarbon? What do you mean by hydrocarbon? Compounds of hydrogen and carbon right like alkane alkene alkyne all this correct so right down on partial oxidation of hydrocarbon on Partial oxidation of hydrocarbon We get water gas We get water gas that is CO plus H2 and then we'll remove the impurity from water gas In order to get hydrogen pure hydrogen and how to remove improved impurity. We have seen that in the last method like boss process okay, so On partial oxidation like for example, suppose we have an alkane Cn H2n plus 2 Plus O2 when you dissolve this in water in the form of the steam basically it converts into CO and H2 partial oxidation If it is not partial oxidation then it gives you directly CO2 over here, right balance reaction is n 2n plus 1 divided 2n plus 1 So here we'll have n and here we have 2n plus 1. That's fine. This balance reaction is this Okay, so this is nothing but the water gas For example, if you take methane the hydrocarbon dissolve in H2O In presence of nickel again the catalyst we are using nickel It converts into CO plus 3 H2 which is water gas and from water gas. How do we obtain hydrogen? We have already sent Yeah, that's right That's what we said. No last method This CO you need to convert into CO2 in order to remove the impurities that is CO present there partial oxidation Is there because you know the complete oxidation of hydrocarbon is a bit difficult Okay, it's not like we cannot achieve it. We cannot do it Right, it's not like we cannot do it but it happens partial oxidation complete oxidation happens at very high temperature and That temperature may be the CN H2N plus 2 decompose it dissociates into carbon and hydrogen again Which is the next method of preparation we have and I is a catalyst Okay, it helps in completion of reaction sooner That is a purpose of catalyst catalyst always, you know finish or completes the reaction in lesser time. Okay We can have two types of catalyst basically positive or negative Positive catalyst completes the reaction at a faster rate Negative catalyst completes the reaction. No, it slows down the rate and the reaction takes more times to finish Okay, so and I here again is a catalyst We're using this as a catalyst at some temperature around 12 to 1300 Kelvin. Okay, and it helps the reaction to proceeds at Faster rate and completes early. Okay, so this is the method of preparation then from water gas We know how to obtain hydrogen. Okay, that's one thing Thermal cracking also we can do directly in this only you write down write down the note over here one note first You write down the process of obtaining the process of obtaining Hydrogen from the process of obtaining hydrogen from the natural gas the process of obtaining hydrogen gas hydrogen from the natural gas is called It's called steam reforming process It's called a steam reforming process steam reforming process We can also have thermal cracking of natural gas Which means you'll take an hydrocarbon suppose CH4 you took and simply you heat this Yeah, I'll repeat just a second CH4 you take and simply you heat this it converts into carbon and This is thermal cracking last note the point I said is the process of obtaining hydrogen from natural gas of obtaining hydrogen from natural gas is known as a steam reforming process Yeah, thermal cracking is nothing. I haven't seen anything here. It's just you take hydrocarbon and heat it Simply on heating hydrocarbon converts into its atomic form that is carbon and hydrogen like this So these are the preparation method of What we say? Hydrogen we have correct now there are few compounds of Hydrogen will see like we have hydrides Water and hydrogen peroxide. Okay, so before that we'll see the properties of hydrogen right down Properties of hydrogen first one it is a colorless Testless and order less gas and order less gas Slightly soluble in water Slightly soluble in water. It's a highly combustible gas highly combustible gas burns with oxygen burns with oxygen with a blue flame blue flame for example, if you write to H2 gas and And O2 it forms H2 burns with a blue flame it reacts with metals metals and forms metal hydrides any plus H2 at around 573 Kelvin Gives to an a H. We'll talk about these hydrides again Yes, it works with all the metals, but different nature of hydrides forms. We'll discuss that separately So what happened? Yeah, so what's your doubt still radiations has energy, right? It dissociates the atom over there Molecule over there and converts into the atomic form like oxygen gains energy What is SR? I just said that energy is low. What energy is no see when you have radiations radiations or you can say It is a kind of similar reaction When we have you know the reaction Photochemical reactions for example we have in presence of light those reactions takes place So light also it it produced the homolysis homolytic cleavage and gives the atomic form of any given atom over there Correct. So in case of radiations also the energy is sufficient enough to provide homolysis and Oxygen converts into its atomic form. That is a nascent oxygen Okay So it's basically, you know, you can understand it this way when you heat something heating means what you're providing energy So radiation also you are providing energy in the form of radiation light if you strike you're providing energy in the form of light So all are the means of you know different means of providing energy and we have different different reactions So usually in presence of light, you know Freeradical forms atomic, you know homolysis takes place and we get the nascent of Atoms like oxygen or any other atoms we get same kinds of behavior. We have in presence of radiations also It reacts with halogen reacts with halogen and forms halides and forms halides like h2 plus plus x2 It forms two Hx and the reactivity of halogen towards hydrogen. It is maximum for fluorine then chlorine Then bromine and then iodine This is the reactivity of halogen towards hydrogen if you look at these orders here We talked about Hf Hcl Hbr and Hi right The bond dissociation energy of Hf is maximum means if you go from top to bottom The bond dissociation energy increases Because of the small size of hydrogen and chlorine bond dissociation energy increases like this Okay, if you talk about bond length bond length From chlorine to iodine as the size increases Bond length bond length increases bond length increases Thermal stability means if you talk about the thermal stability, this is the core order important Must keep that in mind Yeah, I'll tell you wait just a second see bond dissociation energy means what the energy required to break the bond Between the two atom to break this bond. What is the energy required here? That is bond dissociation energy So if the bond length is more Bond dissociation energy will be less because larger bond you can break easily a smaller bond is stronger and difficult to break Right so as the size increases bond length increases you see this as The size increases chlorine chlorine bromine iodine bond length increases bond length increases So bond dissociation energy decreases so bond dissociation energy is maximum for Hf Bond dissociation energy is maximum hence its thermal stability is maximum Right and if you remember I have discussed the acidic order in GeoC the first chapter that we did It is because of the size of an ion done understood this Could you tell me the reason behind this acidic order? I have discussed it. Tell me. Yeah, but why is that so? Mother that's wrong. If you recall In GeoC we have discussed this Are you how it will happen then if you forget like this the things how many of you have revised GeoC in the recent days? Honestly, you tell me. Yes. If you haven't revised you can type in no at least The only problem you have done because if you if you won't yeah, you're done so if you won't revise you won't be you know You cannot recall the one set when it is required GeoC is something like it requires continuous, you know revision. Okay, so in GeoC. I have discussed this concept That acidity is nothing but the tendency of losing H plus ion So you will get F minus the conjugate base And I hope you won't ask me what is conjugate base. Yes If you do not know you can ask me I'm not saying that but I guess you know this what is conjugate base, correct? Yeah, so these are the conjugate base we get all these four orders are important. Okay, copy this down maximum size more distribution of electron uniform distribution and hence it is more stable It is more stable I minus so hi is the most acidity combo Yeah, just give me one minute guys. Just a second. Yeah So these are the few properties of hydrogen we have Okay Now we'll see different compounds of hydrogen mainly three things we have to discuss here hydrides water and hydrogen peroxide That is it. Okay, so write down the compounds of hydrogen. Huh that way also you can think That way also you can think the size is a small so bond length is a small difficult to break the bond and hence difficult to furnish H plus ion That way also you can think next write down The compounds of hydrogen we are going to discuss first hydrides write on hydrogen combines with a number of elements number of elements Forms compound called called hydrides So if you talk about the hydrides of hydrogen You see this diagram first you write down this map actually Hydrides first of all just us again guys just Hold for a minute. Yeah. Hello Yeah, can you hear me? Yeah Yeah, okay, so hydrides we're talking about so mainly three types of hydrides here If you simply try to memorize it will be difficult for you to memorize. Okay So i'm just giving you the pictorial, you know thing so that you can understand in the product table How these hydrides and their properties are? Okay, so first of all you see Like I said, there are three types of hydride so one is We'll discuss the property later. And also there's this. Let me draw this one is we call it as ionic hydride ionic hydride and the second one is We have a metallic hydride metallic hydride and the third one is We have Molecular hydride or covalent. I'll write on covalent hydride These three types of hydrides we have now if you You know try to recall the entire periodic table From left to right. We are going. Okay. So s-block elements that you have s-block elements Forms this type of hydrides ionic After s-block what we have in credit table after s-block what we have D-block right metals so d-block metals forms metallic hydrides So this is formed by d-block elements clear no doubt And after d we have p-block so p-block elements forms Covalent hydrides Okay, so ch4 is covalent p-block ns3 is covalent Okay, uh, we can have yh2 metallic yh3 metallic, okay li la h 0.56 metallic hydrides na h ionic hydrides, okay li h ionic hydrides, okay ca h2 ionic hydrides Okay, so this you understand the private table s-block ionic then metallic and then covalent fine Yes, or no correct now in this we have one exception exception is what? all s-block forms ionic hydrides except bedelium And magnesium bedelium and magnesium forms covalent hydride b e h2 and m g h2 will have here The examples And lanthanum is there no group 3 you see scandium then yttrium and then lanthanum mother group 3 elements if you see On the top we have scandium then yttrium and then lanthanum correct So this is the exception we have b e h2 and m g h2 in fact on a micro level if you see b e h2 is completely covalent m g h2 is partly covalent partly ionic But its covalent character is more than its ionic character Okay, the reason we have that is pheasant's rule. I will discuss that pheasant's rule we have already done Right, so the reason is pheasant's rule here We have more polarization and hence more polarization means more covalent character remember that So this is a brief introduction of hydrides. Did you understand it? Okay Now further this covalent hydride is classified into three categories That is electron deficient Deficient don't write this. Okay Electron rich sorry electron precise And then electron rich So we'll just discuss this one by one the hydrides that forms No, no, no If you have to choose between the one suppose the option is given mg h2 is ionic option is like this mg h2 is covalent mg h2 is partly ionic partly covalent then we'll go with this one partly ionic partly covalent Yes. Yes. Yes. You need to write this entire thing. You need to write Okay But if you have to choose between ionic and covalent will go with covalent not ionic for mg h2 I'm talking about. Yes. Adrijam Yeah So depends what option we have if the option contains partially partially ionic partially covalent Then we'll go with that. Otherwise if you have to choose in between ionic and covalent will go with covalent not ionic Because it's covalent character is more Copy this down and then we'll see this one by one some properties also will discuss Copy it all of you mother run. So first type of hydrides write down That is ionic hydrides ionic hydrides We also call it as salt like hydrides salt like hydrides or We also call it as saline hydrides This is the three different names all are same only this type of hydrides are formed by by elements of Group one and group two except beryllium and magnesium beryllium and magnesium forms Covalent hydrides along with p-block Reason is Fezzan's rule Okay, small size more polarization and covalent character. Okay properties you write down The first one thermal stability thermal stability of these hydrides decreases Down the group The reason is same only as size increases bond length increases and thermal stability decreases So li h is more stable than na h Na h is more stable than kh and rbh Etc Okay group two if you see ca h2 is more stable than srx2 And then da h2 reason is write down as size increases down the group Lattice energy decreases Right as size increases lattice energy decreases thermal stability also decreases Next point to write down density of these hydrides density of these hydrides Is higher than density of these hydrides is higher than To that of to that of the metal From which it is formed Because hydrogen gets you know insert into the pore so mass increases and hence density increases So density is higher One very important property here Except lithium hydride write down except lithium hydride All other hydrides are decomposed except lithium hydrides All other hydrides are decomposed into their parent metal On strong heating So suppose we have an hydride say ca h2 ca h2 go when you heat That's suppose 7 70 kelvin Okay, it converts into ca solid and h2 gas Lithium hydride won't dissociate into this You must keep this in mind the first element The first element of any group shows some abnormal properties What you are comparing stability Yeah group 2 hydride is slightly more stable One last point to write down in this type of hydrides The oxidation state of hydrogen is minus 1 is minus 1