AB Sir

Added: 2026-05-15

[00:00:00]good evening students that is uh what to say you you are still in class 10 you have not got your results but still i can say that you are virtually in class 11 so welcome to class 11 chemistry class okay so today uh i'm going to start basic concept of chemistry i hope you have seen the pdf which i have sent it to you in your whatsapp group you must see the pdf and so that you will come to know that what we are going to do what what are the things we are going to do in this academic year and what is my planning and everything you will come to know okay so without wasting any time let me start the chapter your chapter is basic concept of chemistry the first chapter now in this chapter you'll see in the beginning what we are having is that that is uh we are having that is what is chemistry what are the different branches of chemistry like physical organic inorganic biomolecular analytical industrial so many other we are having then we are having the states of matter solid liquid gas plasma and all those things difference between it now all these things you studied in the lower classes what i am talking to you all these things you studied in the lower classes now here you will be getting that is that is nothing but precision and accuracy and you will be getting also that is some numericals all right uh upon significant figures so that i will teach you that i will tell you when i will be doing the numericals okay that i will tell you i'll teach you don't think that i'm going to skip all these things i'm not skipping it but i will tell you all these things okay time to time i will let you know so when the chapter will be over you will see everything is being talked to you so don't worry about it okay so now today i am going to start that is that is nothing but the laws of chemical combination what i said the laws of chemical combination the laws of chemical combination let me write clearly laws of chemical combination okay from there i am going to start now in the loss of chemical combination you are having five laws you are having five laws the first is your law of conservation of mass which was given by anthony lavish you must be doing anthony lavisher is being considered the father of modern chemistry okay the second law is a law of definite proportion or the law of constant composition which was given by j.l proust or joseph louis proust i have children you are following you are able to understand what i am speaking to you now the third law is the law of multiple proportion which was given by john dalton the third law the fourth law is the law of reciprocal proportion which was given by richter and the fifth law icc student they have studied that is gelusak's law of gaseous volumes law of gaseous volumes we can solve of course when i say loose exactly it is given by gaelic only so these are the five laws of chemical combination we are having it so we are going to study one by one so first we will take the law of conservation of mass which was given by anthony lavish what i said the first law is the law of conservation of mass now what is the definition of this particular law first we i will say the definition of course you see children i will be sending you the pdf uh one that is a pdf which will contain all my notes which i am saying you to you now all these you will find in my pdf in my notes you will be getting it in my notes you will see ah the pdf which i will be sending you will see you initially you will be getting the notes then after that you will get some some important question all right then after that you will be getting the practice paper the chapter test you will be getting one by one okay so after each and every class i'll be telling you that these are the questions you're supposed to do from the pdf and of course you have to do the questions from your book that is uh ncrt the cbs children got it and the iec children either you'll follow kl tube or nutan chemistry we can select okay so for that reason i have written in my pdf which i have sent it to you already that the ncrt pdf i am going to send it to you you can also do the questions from there no need to worry is it children i have written it there again i repeat no need to worry about it you can do the question from ncrt okay fine now next is that is the loss law of conservation of mass what is the definition okay i am saying it slowly you write it down also now this law is in accordance with the law of conservation of energy it is in accordance with the law of conservation of energy now what is law of conservation of energy it states that in a particular chemical reaction total energy remains constant it can only be converted from one form to another form similarly the law of conservation of mass states that in a in any physical or chemical change the total mass of the reactants before the reaction is equal to the total mass of the product at the end of the reaction again i repeat in any physical or chemical change the total mass of the reactants before the reaction is equal to the total mass of the product at the end of the reaction now to explain this particular one i am taking an example i said the total mass of the reactants now very simple example i am taking taking for you now you in the lab you might have done it that is you have taken magnesium ribbon and you have burnt it in air what you got you got residue that is a white residue which is nothing but magnesium oxide so to say all right so what is the reaction i said magnesium it is burnt in air all right to give you that is nothing but two mgo the reaction has to be balanced always now i have to prove it that it obeys the law of conservation of mass now how to do so very simple now the atomic mass of magnesium is 24 so 24 oxygen it is 16 into 2 that means weight of oxygen is 16 16 2 is 32 so how much you got 48 plus 32 so 8 to 10 43718 so total weight of the reactant total weight of reactant how much you got it as 80 gram let us say now for magnesium oxide will say magnesium is how much it is nothing but 24 oxygen is how much it is 16 24 plus 16 how much it is nothing but 40 40 into 2 how much you get it 80 gram this is what total weight of product now what i said you in any physical or chemical change the total rate of the reactant is equal to the total weight of the product you can say 80 gram at the end of the reaction you can see in this way it's a simple example i've given you which you have done it in the lab definitely you might have done it in the lab this particular one you have taken a magnesium ribbon and you have burnt it you got a dazzling white light and you got a white residue in this way you can take another example also and you can see it hydrogen plus oxygen two h two plus o two will give you two h two o in this way you can take it any example you can take it and you can see it naoh plus xcl will give you an seal and water any example you will find the total weight of the reactant is always equal to the total weight of the product at the end of the reaction now this law is given by lavish here okay now we have the experimental verification of this law now this is just an example i have given you now we have the experimental verification of this law i'm rubbing it so experimentally it was not done by it was not verified by rather lavish it was verified by landau all right so what i said landon l a n d o l d apostrophes so i am going to do it now the land dogs experiment what i said you we are going to do the experimental verification so landon what he did is that he took a h-shaped tube a glass tube you can see that a glass tube you can see i am drawing it here which is x shaped all right you can see it here the glass tube which is h set okay now this is also called as h2 or it is also known as landault's tube fine now here you can see two lines are there now what will i do is that i will open this there is an opening here an opening is there got it ah just a cork or whatever you can see it is there you will open it and in this limb you'll add in this limb you'll add that is nothing but let us say silver nitrate solution you'll add it to it in this loop and in this limb what you're going to do is that you add sodium chloride nscl solution now what you do is that you close this cap you close the scalp all right don't deserve it just close the cap got it and what it is that when you close the car there might be some air holes isn't it so you just put some vaseline or you put some wax around it what if you put some vaseline or you put some wax around it so that no arrows should be present in it now if arrows will be there what will happen there might be there might be some what you can say convection or there might be some convection over there can so that that is convection means what happens is that that is uh due to the air hole some energy may go out or you know some energy may come in also all right so as to prevent that so as to see that no energy is going in or coming out all right or any mass or anything we have close the airports to make it air tight that's it fine now what you use that you have closed the cap you have just with the wax or the waistline now what you do is that you turn it upside down you turn it upside down when you turn it upside down what you will see this reaction is going to take place agno3 reacts with nacl to form agcl which is a white ppt this is a white ppt agcl plus nano three you will be getting it but i said a g c l about p d so when you will turn upside down you will get a white typically once you get the white p two ppt you just wait for some time for the reaction to get completed once the reaction has got completed you what you do is that you wait now before that i forgot to tell you that before starting the experiment you weigh these apparatus before starting the experiment you weigh the apparatus all right before starting here after adding a gno3 and nacl use where let us say the weight comes to be as 500 gram what i said you this is weight of reactant 500 gram before the reaction before starting the experiment you have done it now after the reaction has taken place you have got white ppt and the reaction is subsided the reaction has settled down again you take the weight along with this glass tube of course along with the glass tube i got the weight is 500 gram again you take the weight along with the glass tube you will find that the weight of the product is for 99.99 gram it is almost equivalent to 500 gram we can say that now what does it prove it proves that the total weight of the reactant before the reaction is equal to the total weight of the product at the end of the reaction total bit of the reactant before the reaction was how much 500 and total weight of the product at the end of the reaction is how much it is 499.99 we can we can consider to be as 500 grams so from this experiment from this landowner's experiment it has been verified that the total weight of the reactant is equal to that of the product thank you very much