 to apply zinc sulfate zinc sulfate contains you have two minutes to you have two minutes to solve this question zinc sulfate contains 22.6% of zinc and 43.9% of water of crystallization if the law of constant proportion is true then the weight of zinc required to produce 20 gram of crystal will be you have two minutes think apply the law of constant proportion you will get the answer okay please mute your mic all of you okay very easy question percentage is given to you you have to apply law of constant proportion many of you have learnt this okay rnr9 students be quiet rnr9 maybe it is easy for you because you have got this in camon test Tanya in last class I told you law of constant proportion no sir we didn't get okay because rnr9 students some rnr9 students may got this thing because we discussed it okay so answer for this question is you have 10 more seconds okay okay Ashish no don't do this okay fine how to solve this question one minute just a minute I'll show it to you just give me one second okay fine so this is the first question zinc sulfate is given to you those who didn't get the answer first we'll see the leaderboard how many of you got the answer of this question then we'll come to this okay so leaderboard says 38 students have done it right so it's very easy very easy question here you can do so here this is the question how to do the question mass of zinc is given 22.6% 22.6% is mass then how can you do 100 gram if you take if you take 100 gram of zinc sulfate crystal so in 100 gram crystal 22.65 gram is zinc and 43.9% 43. okay then 22.65 gram zinc yes now if you see you have 20 gram of crystal 20 gram of crystal you have so in 100 gram you have 20 this so what is the answer 22.6 gram divided by 100 into 20 this is 4.53 gram 4.53 gram is the correct answer is it clear okay moving to the next question okay students next question is the hydrated salt Na2 SO4.N H2O undergoes 59.9% for a percent loss in gate on heating and becomes an hydrous the value of N will be the value of N will be this is the question the value of N will be okay this question is there is some issue but I know I think you can see so I can't read the question the hydrated salt Na2 SO4.N H2O undergoes 59.9% loss in weight on heating and become an hydrous the value of N will be hydrated salt is losing its water now think sodium is 23 if you want to know the mass sodium is 23 I told you in last class to remember sulphur is 32 oxygen is 16 hydrogen is 1 please apply the concept I told you in last class to remember so the whole centrum is going to be numericals yes but easy these are tough numericals later you will have easy numericals don't worry okay so I think it's time sir okay no so okay fine masses are given 23 sodium sulphur 32 oxygen 16 hydrogen 1 those who don't know but in last class I told you to remember the mass okay only in this question the font is like this in next questions you will you can easily read it okay okay students so I think it's okay fine most of you have answered it right only I tell you how to do this question Na2 SO4 is given to you so you have to calculate because you know that it is a hydrated and an hydrous means all water molecule will go outside like Na2 SO4.N H2O is there it is hydrated when you heat all water molecule will go that's why it is called as N hydrous it will form Na2 SO4 plus N water this is N hydrous now you have you have to calculate this N value you have to calculate this N value so you know that percent is lost is given is 59 55.9% if you calculate mass of mass of water in hydrated salt in hydrated salt in hydrated salt is mass of water is to hydrogen hydrogen masses to isn't isn't a hydrated sodium sulphate basically Na2 SO4.N H2O yes if you know that fact you you have answered then it's well and good it's very good if you know that hydrated sodium salt is 10 H2O very good you can apply that but if you try to go through the concept 55.9% water is the mass of water my water is 18 gram so total number of water molecules are N so 18 into N 18 into N is the mass of water and percentage is 55.9 so total mass total mass of hydrated salt of hydrated salt total mass of hydrated salt is is mass of Na2 SO4 Na2 SO4 if you calculate 23 into 2 plus 32 plus 4 times of 16 plus 18 N it is nothing but 142 plus 18 N 142 plus 18 N this is the mass of hydrated salt now you apply the form percentage 18 N mass of water divided by 142 plus 18 N into 100 is equals to 55.9 by applying this and will come out to be 10 is it clear to everyone is it clear don't think that it is out of your portion in last class I told you you need to remember the mass of atoms and and from now onwards you need to remember 16 hydrogen mass is 1 sodium mass is 23 all these things you need to remember and and once you calculate this this is the formula if this is the percentage if anyone has any doubt don't think that you will always get very easy question you need to calculate it sometimes okay now next question next is now moving to the next one please see the leader board okay okay next question okay the density of salt solution is okay fine so this is the question the density of salt solution is 1.13 gram per centimeter cube at 298 Kelvin the solution contains 17 sodium chloride what volume of solution will contain 38.42 gram of sodium chloride this 17 percentage means mass mass of sodium chloride is 17 percent out of total mass of solution I don't think this question is that tough okay grahesh yes I understand that I did not teach in nephel this thing but you can apply this here the concept that 17 percent mass of sodium is the mass of nsl solution but I think other than nephel all people can do this question and even nephel students can also do this if they apply little bit concept okay fine you still have time percentage of sodium chloride is seven ten out of total mass of nsl solution fine last 16 seconds so show all the options here we can't see it okay fine now okay students I think okay it times up now we'll discuss the question okay most of you have done okay we'll see the leader board after discussing the question okay how to do question is density is given to you try to understand this is the okay the first three questions were tough don't worry those who are not getting answered don't worry next questions will be easy okay this is also little tough questions those who have not used those who are not used to this type of question I have used to solve this type of question the solution is 17 percent sodium chloride so let's say mass of solution is mass of solution is mass of solution is 100 let's say x gram mass of solution is x gram so 17 percent 17 percent of x gram 17 percent of x gram is nothing but 38.42 on solving this x you will get 226 gram this is the mass of solution this will get mass of solution and once you get mass of solution volume is equals to mass by density volume is equals to mass by density 226 divided by 1.13 that will give you 200 centimeter cube if anyone has any doubt please ask if anyone has any doubt please ask no doubts no doubt sure okay I'm moving to the next question okay now the questions will be easy I'm again telling you those who just I want to give you hint before the next question I want to give hint to all of you mole is nothing but given mass given mass divided by divided by molar mass mole is nothing but given mass by divided by molar mass and giving you one example HCl chlorine mass is 35.5 I will tell you mass mass of each atom I will tell you for only for this class not for next class HCl mass is 35.5 hydrogen mass is 1 total mass is 36.5 36.5 u this is for one molecule 36.5 u for one molecule for one mole for one mole it is 36.5 gram just remember this thing whatever you need for one mole it is same like whatever you are getting for one molecule just replace u with g that's it just replace u with g okay so I'm asking you very easy questions 36.5 is for which element 36.5 gram is for one mole of HCl one mole of HCl has this much of gram because one molecule of HCl is this much of u one molecule of HCl has this much of u 36.5 u mass so one mole 36.5 gram okay I'm just giving you a simple question H2 what is the mass of one mole all of you tell me mass of one mole of H2 because for one molecule it is to u so for one mole it is it is it is it is to g last question to all of you last question to all of you what is the mass of one molecule of H2 one molecule molecule is no molecule is not in gram mole is in gram molecule is always in u molecule is always in u very good 32 u but mass of one mole of oxygen mass of one mole of oxygen is 32 gram very good can be did you understand all of you did you understand this and it out in this because in next few question you are going to apply this one step one molecule mass is in always in u the same mass is there for one mole of that thing the same mass is there for one mole of that thing if someone asks her what is one mole it is like dozen only one dozen things are having one dozen things are having how much 12 12 things so one mole is nothing but 6.022 into 10 to the power 23 things this is called as abecadro number many of you know that so those who don't know please remember one mole is these many numbers it is just like one dozen okay okay I'll give you a hint if if if don't worry I'll keep on giving you a hint fine okay so this is the result of last question now we are moving to the next one okay which of the following has the largest number of atoms 0.5 gram atoms 0.5 gram atoms means 0.5 mole 0.5 mole of cu a option is 0.5 mole the option is copper masses 63.5 it is given to you copper masses copper mass mass of one copper atom is 63.5 you mass of one copper atom is 63.5 you yes I know it's very easy it's easy for all many of you 0.5 gram atoms means 0.5 mole 0.635 gram you need to calculate how many moles if mass of one copper atom is if mass of one copper atom is 63.5 you okay I feel that many of you may get wrong in this question if you have not heard me carefully 0.635 gram how many moles it has you have to calculate now you need to check because if moles are more more number of atoms like if you have a two dozen thing and you have four dozen thing four doesn't think definitely have more number of atom a more number of things okay we'll see the leaderboard first then we'll go to the solution of this question oh my god now see students I told you most of you will go wrong in this okay students I told you listen to me why you have not listened I told you which of the following has largest number of atom 0.5 gram atoms I was repeatedly saying the gram atom means small gram atom is a term used for moles so it is nothing but 0.5 mole first is nothing but 0.5 mole first one is 0.5 mole gram atoms I told three times gram atom is more gram atom is more okay 63.5 63.5 gram okay one at one mole is one mole is 63.5 gram copper because one copper atom one copper atom mass is 63.5 you so in last class in last example I told one mole of copper is 63.5 gram so how many moles are there in 0.635 how many moles are there in 0.635 can we pass in B option how many moles are there how many moles are there in 0.635 gram yes it is 63.5 is one mole 0.01 0.01 mole are you getting 0.01 mole no no no see what see apply unitary method one mole is 63.5 gram one mole is 63.5 gram one gram is one by 63.5 moles 0.635 gram is one by 63.5 into 0.635 that is nothing but 0.01 is it clear now 0.0 so how it answer not D okay they have asked your largest number of atoms 0.5 in in this is in A in B it is 0.01 mole in C 0.25 mole and in D you calculate using the same thing 63.5 gram is one mole so one gram will be one by 63.5 one by 63.5 moles did you understand ahaan ahaan did you understand sir okay anyone has any doubt in any part anyone has any doubt in any part see you need to just apply this thing which I told you in last question one mole is the same mass which you are getting for one atom in U that's it and it out why haven't we done this so why have not we done this before okay there is other new questions you are not going to get always the same type of things you need to check this okay and it out okay this thing many students know but these are the little good questions these were asked in competitive exams so you need to understand how to apply the concept okay next question okay Arushi this chapter you will you will learn that in that chapter there are many other things okay we will discuss that that also okay next question okay total number of electrons present in 18 ml of water one mole is I told you one mole is nothing but 6.02 into 10 power 23 you need to just check how many moles are there in 18 ml of water you will get the answer you need to check how many moles are there in 18 ml of water okay how many moles of electron total number of electrons present total number of electrons so the font is quite total number of electrons total number of electron present in okay fine this is the question total number of original six six point two six point zero two into ten four twenty three that is the original value okay those who feel okay fine so students how to solve this question if you have these type of questions so question is six point zero two into ten four twenty three it's okay fine so now one ml of water one ml of water weighs one gram yes or no okay tell me one ml of water weighs one gram because density is one gram per ml 18 ml of water weighs 18 ml of water weighs 18 ml of water weighs 18 gram yes or no and we know that 18 gram water is nothing but one mole one mole of water so one mole of water you have implies if you have one mole of water so what will be the answer six point zero two into ten to the power 23 sir but you asked how many electrons are present so it's not a number of uh it's not the atomic weight so it has to be ten to six point zero two into ten to the pile yes sir there's a C just to be okay six point zero two two into ten to the power 23 moles are there yes these many moles of water okay how many electrons are there in one water ten uh ten electrons very good so it sees the answer right okay answer will be see okay final correct oxygen is eight electron all of you know this thing oxygen has eight electron same like a proton and hydrogen has one electron so total number of hydrogen two hydrogen two electrons so it is ten ten electrons are there so answer will be these many moles because I have asked you electron in one mole of water there is only one mole of electron but if they are okay in one mole of water in one molecule of water 18 is ten electrons implies in one mole of water ten mole electrons so answer will be six point zero two two into ten power 24 okay answer is C i'll correct it answer okay answer is C many of you got it correct i'll change the answer wait answer for this question is C okay just give me one second okay i'll change it in one minute okay answer i've changed it to C don't worry answer is C fine i'm again coming to the presentation okay so okay students now you can see my screen very good many of you got this right it's good thing okay so here so C is the right answer yeah C is the right answer okay fine so now next question how many molecules of hydrogen are there in one gram of hydrogen how many molecules in one gram of hydrogen student please think 18 gram hydrogen has one mole 18 gram hydrogen has one mole so one gram hydrogen is having how many molecules what 18 gram hydro sorry 2 gram not 18 gram sorry 2 gram hydrogen okay you do it by yourself all of you okay sorry sorry 18 gram water i my bad sorry i thought it's water okay you can do it by yourself yes yes 2 gram so is it water or hydrogen no no water water water i'm sorry hydrogen only okay i do i missed i thought i clicked i thought it's water okay okay it's hydrogen only okay how many of you got it correct 22 it's very easy question again see how to do this thank you monisha for correcting this is the this is nothing but next question is okay this is the question just a minute uh fine how many molecules of hydrogen hydrogen molecule is h2 okay it is to you yes or no for one molecule what is for one mole students tell me for one mole h2 how much mass for one mole h2 how much mass all of you please answer for one mole h2 if one molecule is to you okay 2 gram very good so 2 gram is one mole it is nothing but 6.022 into 10 power 23 one mole is 2 gram so implies implies one gram is 6.022 into 10 power 23 divide by 2 i'm again repeating in my last class i told you hydrogen has one u mass if you remember i told you hey okay there is one trick those who don't know hey lina or baby baby allah ke pas kal pin gaye these are the only atoms whose mass are not equal to the two times of their atomic mass okay so what is that hey lina or baby allah ke pas there are two girls lina and baby they went for prayer kal allah ke pas kal pin gaye in these cases it is not two times otherwise i told you hydrogen masses one u so two hydrogen atom are there so two u so mass of one molecule is to you and i told you one concept whenever someone asks you the mole just put the same value with gram with gram okay so two gram and one mole is nothing but 6.022 into 10 power 23 implies one gram is this much molecules any doubt okay this is a trick to remember like which all atoms are not having mass equal to the two times of their atomic number is it clear okay next question okay no no okay students now we are moving to the next question total number of moles of sodium oxide in 620 gram of it those who don't know mass of sodium for them okay i know this is easy for many of you but sodium mass is 23 oxygen mass is 16 now do it sodium mass is 23 oxygen mass is 16 what happened with the how how it has taken all your points uh okay it happened with you i think anyone else has faced the same issue okay students so number of moles i think this time you will get correct answer those who are making mistakes in these questions will see the lead report first okay most of you got it right how to do this so this is the question sodium is sodium oxide na2o first you need to know that formula of sodium oxides na2o because oxygen is 2 minus sodium is plus 1 so formula is na2o once you get the formula of sodium oxide 23 is mass of sodium atom there are two sodium atoms 2 into 23 mass of oxygen is 16 so it is 23 into 2 plus 16 that is 46 plus 16 yes or no so like that now you have 620 gram 620 gram it is nothing but it is 62 62 u one molecule of na2o is 62 u 2 one mole of na2o is is is 62 grams 62 gram implies 620 gram is there in imply 620 gram has 10 moles any doubt students if anyone has any doubt please ask no fine next question okay good students many of you are okay very good part okay fine next question please read question carefully these are all all you can say these are all ntsc level questions so 2 gram of oxygen contains number of atoms equals to it carry if you have 90 seconds to solve this question you have to check one one option one by one option those who don't know mass hydrogen is one hydrogen atom has one u sulfur is 32 u nitrogen is 14 u sodium is 23 u you can ask me anything if you have any doubt in masses mass of any atom i will tell you you have time one more minute take your time and solve this question okay yes nitrogen is 14 u students nitrogen is 14 u 32 yes sivam sulfur is 32 okay students we'll see how to do this first we'll see the reason okay 35 of you got it right very good students okay we'll see how to do those who didn't understand this part we'll discuss so question is very easy okay question says okay one minute yes this is the question 2 gram of oxygen not 2 gram of 2 gram atoms it is 2 gram of oxygen contains number of atoms okay oxygen masses one more one mole of oxygen is one mole oxygen is 16 gram okay implies 2 gram is 2 gram of oxygen is having 1 by 16 into 2 moles that is 1 by 8 moles 1 by 8 moles so if anyone if any if in any case if you are getting 1 by 8 that will be the answer so if you see 4 gram sulfur sulfur is sulfur 1 mole is sulfur 1 mole is 32 gram implies 4 gram is 1 by 8 more yes or no any anyone has any doubt no okay students in next question in next question it is little tough but if you understand one thing just remember just one thing is used I'll tell you I'll tell you the volume of STP okay I'll help in that I'll help you in that question then you will be able to solve that okay let me first show you the question okay good Karun now those who are not able to read the question I will show you here the volume of gas at STP volume of gas at STP is this okay calculate the number of molecules in this number of molecules in this okay so just just consider just that's why I told you just consider you have most equals to you you have most equals to 5 into 10 power minus 12 moles now solve this question 5 into 10 power minus 12 more solve this question volume the the moles of the gas is given to you 5 into 10 power minus 12 how to solve this I think now it has become easy for you moles is given to you you have to calculate its molecules okay in which textbook there are three classes in this in the centre mark in rnr 9 nephel 9 and nephel 9 nephel students you will have it on in third chapter no you will have it in 10 don't worry nephel you don't have this mole concept in detail okay sir so what about rnr in ncrt you will have in this chapter only and for rnr you have little bit idea of mole concept if you have the moles you will have number you can calculate number of molecules like so what about rnr yes rnr students you know I told you little things about the moles what is the mole if you remember abe gato's law do you remember we discussed abe gato's law sir not rnr inr okay rnr you will learn in this this chapter only atoms and molecules but after some time it is the last thing okay so moles it is given to you 5 into 10 for minus 12 moles so number of molecules is in one mole something number of molecules is 6.02 into 10 for 23 because mass is not given these many molecules so time's up okay yes one minute so one mole is these many molecules implies 5 into 10 for minus 12 moles is 6.022 into 10 to the power 23 into 5 into 10 to the power minus 12 this will be the answer is it clear okay so now answer will be 3.01 into 10 power 11 there is uh no 12 b is the answer okay many of you got it right good students next question okay is this namrata from inr namrata are you the same namrata from inr or someone else okay number okay the number of molecules in 16 gram of methane number of molecules in 16 gram of methane calculated number of molecules in 16 gram of methane methane carbon mass is 12 hydrogen is 1 now don't ask me sir what is methane formula you are expected you are supposed to know this what is methane formula i think most of you know hydrogen is 2 amu right hydrogen is one amu one hydrogen hydrogen molecule is 2 amu because it is x2 okay okay for many of you it is easy and okay fine one minute fine how to do this okay now see 16 gram of methane methane is cx4 carbon is 12 hydrogen is 1 total one molecule mass one molecule mass is 16 u one mole mass is is 16 is 16 gram is 16 gram yes whatever mass of one molecule is there this is mass of one and the answer is this hope you understood this one mole is nothing but 6.02 10 red port 23 any doubt students you have any doubt okay fine next question very good students now next question is in front of you how many moles of electron wave one kilogram how many moles of electron wave one kilogram okay so for hint i can tell you mass of electron is 9.1 into 10 to the power minus 31 kg for the hint mass of electron is 9.1 into n to the power 31 kg mass of electron 9.1 into 10 power minus 31 kg you can solve it electron mass is given to you i think it will be easy for you to answer now now how many moles of electron wave one kilogram okay fine so how to do this question still you have some time left okay students now i'll tell you the answer okay still you have 19 seconds students you should see the time that's why i've given you time so that you calculate the property okay i think it times up now fine many of you are wrong in this question okay fine i'll see i'll tell you how one electron mass is this much okay one mole electron means one mole electron means 6.022 into 10 to the power 23 electrons electrons one electron is having this much mass okay so they have asked you one kilogram so just apply unitary unitary method here 9.1 into 10 power minus 31 kg has one electron implies one kg has one kg has one by 9.1 into 10 to the power minus 31 electrons yes or no now these many electrons you have so you have to tell the answer what is the answer for this okay so 1 by 9.01 into 10 power minus 31 but they have asked you how many moles how many moles they have asked these many electrons are there they have asked you moles so what i can say in one mole electron these many electrons are there so using equation 1 and 2 what can i say 1 by 9.1 into 10 to the power minus 31 electrons are nothing but nothing but 1 by 9.1 into 10 to the power minus 31 into 1 by 6.023 into 10 to the power 23 moles this is by equation 1 and 2 okay students please ask if you have any doubt in this please ask just apply simple math here any doubt students any doubt please say yes or no okay fine one kg of electron is this much one kg has these many electrons any doubt in this in equation 1 in equation 1 any doubt because one electron has this much mass applying unitary method one kg of electron will have these many electrons one kg of electron yes or no someone asked this question please tell me someone told me to repeat this tell me your name Janvi of who please tell me who asked Gandha these are the one kg of electron has the one kg of electron carries these many electrons yes or no and one mole of electron has these one mole of electron has these many electrons so you need to tell me how many moles are there it's like you have 25 bananas and if i ask you how many how many dozen are there how many dozens of banana you have what you will do 25 divide by 12 yes or no because in one dozen you have similarly whatever i'm getting i have divided it with 6.02 into 10.23 is it clear okay definitely we will have this in r in r class in detail don't worry don't worry because uh fine next question we'll discuss this in detail okay my next question which has a maximum number of atoms mass is given to you atomic mass is given to you in bracket carbon has atomic mass 12 carbon has atomic mass 12 atomic mass is given in bracket they've asked you maximum number of atoms maximum number of atoms in bracket they have given atomic mass so like aluminium is 27 means one aluminium atom has 27 you go with the help of moles you will get the answer very easily proceed with moles okay fine how many of you felt that this question is easy how many of you felt that this is easy oh way too easy fine okay student i'll tell you it's very easy question okay let me see how many of you got it right fine 26 not bad number okay fine see this is the question i told you my dear students carbon atomic mass is 12 so i can say that 12 gram of carbon is nothing but one mole of carbon it is nothing but one mole of carbon 27 gram of aluminium is nothing but one mole of aluminium 108 gram of ag is nothing but 108 gram of ag is nothing but one mole of one mole of ag and the last is 56 gram of iron is nothing but one mole of iron i'm not getting where you people are going wrong one mole of iron so only thing is this 24 gram of carbon because 12 gram has one mole implies 24 gram will have two moles yes or no any doubt okay don't worry don't worry if you have you will understand it later if you are not getting now i'll explain it in class okay any other doubt no doubt next question yes yeah tell me what is your doubt okay there are total okay fine this was the last one oh sorry oh congratulations number so i thought there is one more question okay good congratulations number okay if anyone has any doubt please ask now we have three more minutes left no worries tell me if anyone has any doubt actually i thought there is one more question that's why i took it