 अव च़न रफ च्रोव दोे रह। प्च्ड़े म्सुसर्टे है ڈ execut ڈ contains 22.6 gram of zinc and 43.9 gram of water of crystallization. ڈ if the law of constant proportion is true, than the weight of zinc required to produce 20 gram of crystal will be. ڈ not very tough question ڈ not easy ڈ also. ڈ but you have time. ڈ you have one minutes 40 seconds left ڈ think about it ڈ and then answer ڈ solve it properly. म appliance bike answer of first question is 36 students okay fine still it's a majority of you have done it right ring sulphate crystal is given to you okay okay now see Zinc-sulfate contains 22.6 ॐ 22.65% is given to you And it is 40.9 gm of water of crystallization The weight of zinc requires to produce 20g of crystal 20g of crystal So for 100g of crystal 20 gram crystal mass of zinc required is 22.65 gram implies for 20 gram crystal how much mass 22.65 divided by 100 into 20 gram is answer it's very easy if I would have given you if I would have given you the anhydrous thing then cushion becomes little tough yes is it clear to all of you all of you got the answer could I move to the next question good you should not make mistake we are not mass so shouldn't we multiply by 10 what sir we are calculating the mass of zinc required we are suppose to find the rate so shouldn't we multiply by 10 why we multiply by 10 it's 20 gram they have given okay found what they have asked then the weight of zinc yes weight is 20 gram only weight is whatever if you calculate what you are going to get it is like 80 it's like something like point no 44 and if 88 it's something like point what answer you are getting this 45.3 45.3 is the answer yes or no the answer is B 1 minute 1 minute what mistake 4.53 1 minute what yes 22.65 into 20 it is 4.53 not 45.3 4.53 it is 4 times yes what doubt you have we are the mass mass is a gram mass is 4.53 I agree with that but weight should be multiplied by 10 why weight should be multiplied by 10 okay you are saying that gravity you will no no no see that gram itself is you have considered the mass then only you have considered the gravity then only you are getting in grams understood you have considered so weight whenever I am saying that is something is having a 20 gram weight it means that I have already considered the gravity if I am saying what is your weight you will say 45 kgs I have already considered the gravity understood okay you have thought in a different direction but it's well it's good you have thought in that sense I am very happy for that but you understood the point yes or no hello did you get the point okay fine next question so mass is always okay whenever you are calculating something in grams that grams is you have considered the gravity okay fine okay next question be ready for that okay if you are not able to read the question I will change yes this is the question the hydrated salt Na2SO4 undergoes 55.9% loss in weight on heating and become n hydras the value of n will be the value of n will be you have 37 seconds left the hydrated salt Na2SO4.n H2O undergoes 55.9% loss in weight on heating and become n hydras the value of n will be okay students it seems like time's up and the data says that oh my god 23 students have answered it right but more than them people have made mistake fine you know you can use one thing okay fine how to calculate the hydrated salt it undergoes 55.9% weight on heating and become n hydras become n hydras so how to solve this if it has become n hydras means the mass of water is nothing but weight of water is nothing but okay try to understand sodium mass is 23 sulfur mass is 32 oxygen mass is 16 hydrogen mass is 1 oxygen mass is 16 so these weights I think you all know problem in learning the weights anyone has any issue in learning the weights please let me know now only okay fine you are supposed to memorize the weight okay I will tell you one trick to all of you so you know generally till atomic number 20 okay do you know atomic number all of you know the atomic number of elements till 20 Anish all of you know yes if you know atomic number I will help you in learning the weights till atomic number 20 generally mass generally mass is equals to 2 times of atomic number generally mass is equals to 2 times of atomic number this is general thing okay its double but but there are many cases where you cant apply that lets say phosphorus atomic number is atomic number is atomic number is 15 mass is mass is 31 so its not following the double if you double it you cant get mass so I will tell you one trick to remember you know there were two girls one name is leena and one is baby there were two girls named leena and baby okay they went for prayer so they went for prayer so how you will call this statement leena its in Hindi okay leena or baby Allah Allah ke pas kal fir gaye this is the trick which I made if it helps you its very good okay leena or baby Allah ke pas kal fir gaye so these are the elements if you see these are the elements lithium, sodium, argon, beryllium, boron, aluminium potassium, phosphorus, chlorine and chlorine these are the elements where this rule is not applicable till atomic number 20 and other than these elements you can directly multiply the atomic number with 2 you will get the mass number is it clear so how to remember leena okay gaye leena or baby or haleena baby whatever because hydrogen is also there hydrogen has atomic number 1 mass is also 1 but you all know the hydrogen thats why I have not included hydrogen in that okay kal fir gaye means yesterday also yesterday also they went to church gave went to mosque so leena or baby Allah ke pas kal fir gaye that is kal fir gaye understood fine so these are the elements where you cant get the mass multiplying by 2 example leechium, hydrogen, aluminium, leechium atomic number is 3 but mass is 7 just multiply it with 2 and add 1 sodium atomic number 11 but mass is 23 multiply 2 add 1 argon atomic number 18 but mass is 40 multiply by 2 plus add 4 verilium 4 but mass is 9 multiply by 2 add 1 boron 5 but mass is 11 multiply by 2 add 1 aluminium atomic number 13 mass is 27 multiply by 2 add 1 potassium 15 mass is 31 multiply by 2 add 1 okay sorry potassium is this not phosphorus potassium is potassium is what is the atomic number of potassium 19 yes but mass is 40 multiply by 2 add 2 phosphorus 31 and 15 chlorine 35.5 and 17 chlorine 9 and 19 so if you see multiply by 2 and add 1 is applicable in all these cases multiply by 2 and add 1 is 7 23 other than okay verilium it is applicable boron it is applicable aluminium it is applicable okay why I am telling this because you all are preparing for competitive exams and you are supposed to learn all this it is applicable and chlorine it is applicable it is not applicable for only 3 4 7 only for 3 atoms it is not applicable argon chlorine and argon chlorine and potassium for these 3 it is not applicable otherwise everywhere you multiply by 2 and add 1 understood okay 1 minute is it clear is it clear to all of you these 3 cases mass is not not followed the thing multiply by 2 and add 1 okay 1 minute 1 minute oh sorry it is not 40 it is 39 yes you are right but here also okay 1 minute so argon and chlorine sorry sorry potassium is 39 only 19 into 238 but potassium has isotopes which are of the atomic number 40 okay yes it has the isotope but if you see the periodic table in periodic table you know we will see the most abundant isotope we will see the most abundant isotope so generally if you ask about the atomic number if you see the periodic table what is there in the periodic table if you reference the periodic table you will see that potassium is written as 39 mass only okay the most abundant is 39 one is it clear okay fine yes or no okay so these only in these 2 cases argon and chlorine you can remember moving to the next question we have spent too much time in this but I think you learnt something yes or no have you learnt something fine next question so for the most abundant isotope fine next question okay please see the timings timings may vary okay you may face the issue with okay this is the third question this is the third question okay students still you have 13 modes 1 minute to answer this question don't worry we will finish the quiz very early not very early but on time don't worry the density of salt is given to you solution has this much percentile volume of this is given to you is it easy or tough rate it definitely your leader board will rate that but still I want to know from you you have 17 more seconds okay fine I will explain okay in last I will explain at the end of the session okay fine so answer for this is oh my god only 15 students have answered it right okay no problem we will see how to do see the question is given to you is the density of salt solution is there if density is given to you and they have asked you density is nothing but mass of solution divide by volume of solution yes or no so what you can write density is density of salt solution is mass of solution divided by volume divide by volume of solution divide by volume of solution this is density it is nothing but 1.13 gram per centimeter no problem the solution contains 18% sodium chloride whenever someone gives you the mass whenever they are not giving anything we will consider the mass percent is given means in a 100 gram of solution in your 100 gram of solution mass of sodium chloride is in 100 gram of solution mass of sodium chloride mass of sodium chloride is is 17 100 gram solution mass of sodium chloride is 17 17 gram okay what volume of solution will contain 38.42 gram of NaCl no problem if you calculate in 100 gram solution mass of sodium chloride is 17 gram unitary method what I will write like this in 17 gram NaCl mass of solution is mass of solution is 100 implies in 38.42 gram NaCl mass of solution is 100 by 17 into 38.42 gram this is the mass of solution you got they have asked you volume of solution can't you use the density can't you use okay tell me this will come out to be this will come out to be 226 gram this will come out to be 226 gram so 226 gram of solution you have so mass of solution you have 226 gram mass of solution is 226 gram density density is 1.13 gram 1.13 gram can't you calculate volume is it tough tell me is it a tough question no okay no no no 17 percent whenever given to you whenever nothing is mentioned we will consider mass by mass only understood any other doubt no could we move to the next answer is B only I am moving to the next question all of you are fine with this yes or no okay fine so next question is so this is quite disappointing that only 15 students have answered it right it is not very tough question for a 10th grader but fine you should work hard okay very good who is leading today very good next question please read question carefully and see timings also now the timings are less for the questions which of the following has the largest number of atoms in this question be little careful be little careful this topic is very very important for all the competitive exams you have last 10 seconds largest number of atoms okay fine I think we will see how many of you have done it right you know answer is A and I told you my dear student be little careful be little careful you people have answered it A one minute okay answer is A last one minute we will see the question you know what do you mean by 0.5 gram atoms and even know 0.5 gram atoms what do you mean by gram atoms what do you mean by gram atoms gram atoms is nothing but means moles so 0.5 gram atoms is there this means 0.5 moles I told you be little careful 0.5 moles 0.635 mass is given okay moles we will do this question with the help of moles moles is nothing but given mass divide by molar mass given mass divide by molar mass or atomic mass whatever here you have a copper atom copper atom you all know 63.5 is the mass of copper atom so 0.635 divide by 63.5 it is not it is almost 0.01 mole 0.01 mole copper atom 0.25 mole given in question fine 1 gram of copper this means moles are moles are 1 divide by 63.5 definitely it is very very less answer will be A that is 0.5 is the highest number is it clear to all of you 0.5 mole is the highest if anyone has any doubt please ask so this is how you will get fooled by the examiner is it clear to all of you yes or no gram atom this is a definition 1 gram of atom is different thing 1 gram of atoms is different thing gram atom is 1 mole whenever gram atom you see in your life tell it as a mole only understood is it clear whenever you see gram atom it will be mole this is the definition of mole fine next question ok this is very interesting to see this time many of you have lost your positions no no no worries you have more chances to get back your position and to improve also now in this question my dear student please see the timing 30 seconds you have yes exactly this was there in class 9th also and this is there in class 11th also unfortunately it is not there in 10th you should know this thing total number of electron present 30 seconds ok it seems like time is less for this because many of you have not answered ok 17 only see students no worries we will discuss how to do it is very easy question if you see there was number of electrons in 18 ml of water density is 1 gram per ml this means in 18 ml mass of water is mass of water is 18 gram mass of water is 18 gram yes or no no worries no worries please listen to me carefully 18 ml means 18 gram yes or no implies moles of water moles of water is 18 by 18 because molecular mass of water is 18 because H2 or all of you know 16 is the mass of oxygen one is the mass of hydrogen total masses 18 there are two hydrogens 1 and 1 so total number of moles is 1 mole so many of you have answered because of seeing this one mole many of you have answered as A but A is not the answer why in water you have in cushion they have asked total number of electrons present in 1 water molecule how many electrons in 1 water molecule how many electrons all of you tell me number of electrons in 1 water molecule in 1 water molecule how many electrons I have not asked very tough question 1 water molecule how many electrons water is X2 and O just count the electrons 10 for 23 things so in 10 moles in 10 moles 6.02 into 10 power 23 into 10 any doubt any doubt in this you can ask if you have any doubt no worries at all all of you got this yes yes only for this question okay I thought I think that you people had less time but don't worry in next other in other questions you will not face any difficulty in timing okay next question I thought that you will able to finish this in time okay no problem see next question okay one minute I'll fine I'll remove this now so Namesh is meeting it seems okay next is we ready for that here you have timing of 60 seconds I think 60 seconds you are 30 seconds 30 seconds please read the question carefully 30 seconds very easy question 30 seconds are 30 seconds are not less for this question what I feel what do you say students okay answer is B and most of you have answered it right only fine very easy question H2 mass is 2 gram because H2 molecule they have asked one one mole of H2 molecule is 2 gram okay so one mole of H2 is 2 gram implies in 1 gram half mole of H2 half mole of H2 and half mole is nothing but 6.022 into 10 to the power 23 divided by 2 you should if you should select the option best option is B is it clear why 22 why 22 why 22 tell me any kid is it clear fine moving to the next question anyone has any doubt please ask now only no doubts sure hope you are learning something yes or no okay fine next question one minute you have one minute you have okay any kid but could you read now that's why i'm sharing my screen okay fine so number of moles of sodium oxide i told you mass of sodium oxide your mouth you know yes yes okay students so still you have 12 seconds okay time is up let us see how many of you got the okay 35 of you have answered it right no problem sodium oxide is NA2O if you have made mistake in writing formula then i can't do anything okay because NA plus and O2 minus will form NA2O so mass of sodium oxide mass is nothing but 23 into 2 plus 16 that is 62 grams so mass is 62 grams means that is one mole one mole is 62 gram 62 gram will have 10 mole any doubt any doubt in this short next question okay this time nana has answered very fast but still see my screen one minute one minute one minute can you see my screen students don't worry don't worry okay fine i'm going to show you the next question okay one minute it has started again i it seems just a minute we have question till 7th one yes okay fine do next question this is 8th one 2 gram of oxygen contains number of atoms equals to that in okay fine one minute okay 20 more second students with instead of 2 in our last year's reference book misclicked i'm so proud okay fine so students answer for this is okay so most of you have answered it right only we'll see how to do 2 gram of oxygen contains number of atoms equals to that in so 2 grams oxygen means if you see moles of oxygen moles of oxygen is given mass divided by atomic mass 16 atomic mass of oxygen is 16 i told you and start that is 1 by 8 1 by 8 moles so you need to see which is having a 1 by 8 mole so this is not having 1 by 8 mole because 0.5 gram divide by 1 is not 1 by 8 4 gram divide by sulphur mass is 32 this is 1 by 8 it seems correct answer nitrogen 7 by 14 no it's not 1 by 8 is 1 by 2 nitrogen mass is 14 sodium 23 divided by 23 divided by 2.3 divided by 24 that is 1 by 10 is it clear to all of you yes or no could i move to next one very good next question next question is okay we ready for that the volume of gas at stp volume of gas at stp okay i will help you a little bit in this question volume of gas at stp is 1.12 into 10 power minus 7 centimeter cube centimeter cube volume of gas is 22.4 liter at stp 1 mole gas is 22.4 liter this much i can help you 1 mole is equals to 22.4 liter at stp this i can help you now do it by yourself it doesn't matter it doesn't matter no whatever gases okay fine yes it is same for all the ideal gases okay fine so students how to answer this question b is the answer and many of your answer is right 1.10 centimeter cube okay fine you have this much centimeter cube i told you 1 mole is 22.4 liter 1 mole is how many centimeter cube 1 liter is equals to 1000 centimeter cube so 1 mole is equals to 22.40 0 centimeter cube this is 1 mole of gas you have these many you have this much volume so how many moles of gas 1 divided by 22.400 into 1.12 into 10 power minus 7 moles you will have these many moles you have yes they have asked you number of molecules number of molecules is 1 by 22 224 00 into 1.127 into 10 power minus 7 into 6.022 into 10 power 23 is it clear any doubt students you have any doubt then ask tell me many of you have guessed because it is like the only nearest answer is this b 23 minus 7 nearest answer seems like this yes okay next question okay 10 to 1 the number of molecules in 16 gram of methane is you have only 13 seconds 16 gram of methane only 30 seconds number of molecules in 16 gram of methane okay students times of extremes b is the answer very good answer is b 16 gram methane mass of methane is also 16 gram so answer is 16 divided by 16 that is 1 mole and 1 mole is nothing but 6.0 into 10 power 23 molecules is it clear next question okay fine moving to the next one very good namesh fine next question how many electrons weigh this now this is a good question for you you need to remember what you did in this is a 2 minutes you have please take your time and do it how many moles of electron wave 1 kilogram wave 1 kilogram if you know mass of electron then only you can proceed mass of electron if you don't know mass of electron i can help you 9.1 into 10 power minus 31 kg mass of one electron 9.1 into 10 power minus 31 kg okay one promising and correct so you have one more minute left 50 seconds left solve it properly and get the answer 50 have already answered good okay answer it fast students okay fine still you have time those who still didn't able to finish this mass of electron you learnt in class 9 mass of electron charge on electron what is charge on electron those who have completed please tell me charge on electron what is charge on electron fine answer is b and most of you got that 28 students got the answer fine what is that mass of one mole of electron wave so mass of one electron is this mass of one mole of electron one mole of electron is 9.1 into 10 power minus 31 into this is this is mass of one electron in kg mass of one mole is 6.022 into 10 power 23 yes or no okay thank not visible so please sing okay rank not visible now fine i'll wait for that is it clear to all of you any doubt okay okay one minute one minute how many moles of electron wave one kg you need to calculate moles sorry mass of one electron is 9.1 into 10 for minus 31 kg so how many moles one kg has one divide by 9.1 into 10 for minus 31 mole okay earlier i gave this so that you can remember i why i gave more time so that you can remember this thing but i thought that you people will not do anything if i don't tell you the mass that's why i revealed that fine next question one mole of electron is 1 by 2200 gram no no one mole of electron okay one minute we'll discuss it just a minute okay now no no it's not not not correct my dear that is that is the mass of electron is this much times mass of proton that's fine but mass of proton is not one gram mass of proton is not one gram last 10 seconds is very easy question okay fine we'll discuss so this is the question what is the maximum number of atoms 24 gram mass of carbon is 12 to two moles 24 is two moles 56 is mass of atom one mole 27 one mole 8 one mole very easy question that's why i kept time less sensor is 8 hope you understood this so could you repeat that one minute which one this one this one or last one prisham this one only answer to my question oh one mole that okay you know mass of any electron is one by one eight two zero times then the mass of proton yes like proton mass is proton is two times two thousand times heavier than electron but proton is not one gram understood understood prisham proton is not one gram so you can't write like this one amdu is fine yes one mole of electron is there then you can say one gram one more of protons are there then you can say one gram okay so i think based on that also prisham just wait for few minutes i will tell you with the help of that also you will get answer near to what i have shown if you have done like that i don't think that you are wrong but you will get answer near to that that thing only understood okay we will discuss after this let me finish two more prishams then we'll discuss yes yes you got approach answer yes you have approach is right it's not wrong at all okay fine it's good that you remember that part that's good part that's good thing okay this is the question you have your time please do this an organic compound of molar mass 108 gram per mole per gram per mole c h n atoms are present in 9 is to 1 is to 3.5 by way molecular formula can be very easy question you have 20 more seconds okay c 6 h 8 n 2 c 7 h 10 n c 5 h 6 n 3 c 4 h 18 n 3 you could have asked me earlier so i would have told you that thing c 6 h 8 n 2 c 7 h 10 n okay fine i think it stands up answer is a very good students you know an organic compound molecular mass 108 gram per mole hydrogen and are in this ratio okay you can consider it like this 9x 9x is mass of hydrogen mass of mass of carbon 1x is mass of mass of hydrogen 3.5x is mass of nitrogen i am using simple mathematics 9x plus 1x plus 3.5x is equals to 108 gram calculate x value 10 13.5 so it is 13.5x is equals to 108 what is the x value you are going to get what is the x value at 108 by 13.5 okay then this is the x but your mass of carbon is 9 that is like 9x a mass of so hydrogen how much it is almost like it is almost like eight times it are almost like eight so this is eight almost eight so you will get answer like this is it clear once you get that so hydrogen eight is this option answer is eight hydrogen eight is this any doubt any doubt no last question i i guess last question of today's quiz let's do it very good name saksa visa or we are doing great all of you last question the number of molecules in 335.5 gram of chlorine gas 3.011 into 10 per 23 6.022 into 10 per 23 9.033 into 10 per 23 1.2044 into 10 per 24 you have 10 more seconds left 13 more seconds okay this is very easy question 35.5 gram is one chlorine atom yes okay one minute why you people have made mistake in this one minute one minute 35.5 chlorine gas chlorine gas one chlorine atom is one chlorine atom is 35.5 chlorine gas is cl2 yes it is a so they have asked number of molecules so chlorine is her 70 so number of molecules is a number of molecules is a is it clear to all of you is it clear to all of you this is very disappointing students why you are making mistake in these type of questions oh my god 14 students only so you must have realized that what mistake you all are making okay no problem fine we will see who will congratulation namesh aksha disha karan and lux all of you okay still it's still we have some question one minute one minute no no no i think there is nothing okay there is nothing in this don't say don't write anything there is nothing i guess okay fine now you are having the results no no there is nothing in that namesh is the winner congratulation namesh congratulations fine okay now namesh aksha disha karan lux naina all of you you have performed very well i think you must have learned something today new and you must have brushed up the old things with more clarity which is a very important topic for your competitive exams any two so forth question okay so it is very easy question mass of sodium is 23 sulfur is 32 oxygen is 16 hydrogen is 1 oxygen is 16 if you calculate mass of sodium sulphate if you calculate mass of sodium sulphate dot n h2o so how you are going to write how you are going to write 23 into 2 plus 32 plus 16 into 4 plus 18 into n this is mass of hydrated sodium sulphate 55.9 is loss in weight on heating means 18 n is nothing but 18 n is nothing but 55 percent 55 percent of total mass of total mass this means that 18 n divided by total mass divided by total mass is nothing but into 100 is nothing but 15 calculate n you will get the answer understood understood someone ask this question is it clear this is the molecular mass this is the molecular mass and 18 n is the mass of water that is 50 okay fine you know many many people can guess like this they know that any 2 so forth dot n h2o dot n h2o is the compound you all know that is bossing soda so i think many of you have guessed this and then answer 55.9 it is okay fine it is 55.9 sorry okay okay okay 55.9 is it clear yes or no you will find that n equals to 10 any other doubt any other doubt someone ask one more question okay it's like moles are nothing moles are something which are like 6.02 into 10 to the power 23 things are the moles if you tell about in terms of atoms and molecules if you talk about atoms and molecules in terms of atoms and molecules moles is nothing but their molecular mass okay given mass given mass divided by their atomic mass okay now we will say sir why you have written like that because one thing you need to understand i told i taught you in last year also those who learned from like if i talk about nitrogen nitrogen mass is 14 am you this is one atom mass of one atom but one mole of nitrogen atom weighs 14 gram that you need to understand just replace the am you with am you with gram whenever you want to calculate mass of any mole mass of mole of anything is nothing but am you replaced with gram if you have water that is 18 am you that is a one molecule mass but one mole of water is 18 gram so so if i have 36 gram of water how many moles anushka if i have 36 gram of water how many moles two moles i have applied in this formula given mass is 36 molecular mass is 18 that is two yes or no understood is it clear anushka okay any other question question number 11 wait could i erase this anushka could i erase this yes or no okay fine 11 question 11th is this mass of moles of electron weighs one kilogram so mass of electron is 9.1 into 10 for minus 31 kg mass of one electron okay so one kg of electron one kg of electron has okay mass of one electron is this one kgs electron and how many electrons one kg of electrons have how many electrons one by 9.1 into 10 for minus 31 electron that is one kg of electron they have asked you how many moles of electrons are there so these many electrons in one mole 6.0 22 into 10 for 23 electrons yes so apply the unitary method between these equation 1 and 2 in one mole these many electrons so in these many electrons how many moles in these many electrons how many moles one more has this many electrons so these many electrons have 1 by 9.1 into 10 for minus 31 divided by 1 by 6.0 22 is it clear is it clear someone asked question number 11 yes or no fine is it clear all things are clear all things are clear students hope you learned something and this is a very important topic for your board's exam so for your competitive exam preparation okay students thank you we'll meet next week with new topic bye