3 AVERAGE MOLAR MASS | MOLE CONCEPT | Chemistry By ALK Sir | IIT JEE Main and Advanced

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AVERAGE MOLAR MASS | MOLE CONCEPT |Physical Chemistry By ALK Sir | IIT JEE Main and Advanced #admission_online_offline_batch_7410900901 #Competishun
This is Lecture 3 of Mole concept which covers average molar mass and relevant Jee Problems The detailed explanation of the lecture with timestamp-:
00:00 - 02:02 Average atomic mass /Average atomic mass -17Cl35 (75%) and 17Cl37(25%) So average molecular weight of chlorine M avg=35.5g/mol.
02:03-06:12 Isotopes are atoms of same element with same atomic number but different mass number. For e g :1H1,1H2,1H3 and C12 , C 14.Formula for average atomic mass Mav=(Total mass of all the atoms in the sample)/(Total number of atoms ) or (Total mass in g)/(Total number of moles) in g/mol
06:13 - 08:16 Calculation of average atomic mass when % by mol abundance of isotopes is given E g A+B is given Let A is x% and B is (100-x)% by mol or by number M avg=x*M-A+ (100-x)*M-B/100 M avg=x1M1+x2M2+x3M3.... /100
08:17 - 12:17 Note: In a mixture % by mol of a component need not to be same as % by mass of that component .E g A+B A-x% and B-(1000-x)% by mol % by mass of A=% by mol of A*M-A/M avg
12:18 - 14:12 Dry air (O2+N2) O2 is 20% and N2 is 80% by mol: (i) M avg = (20*32+80*28)/100 =28.8 g/mol (ii) % by mass of O2=20*32 /28.8=22.22%
14:13 - 19:50 Explain which is denser : Dry air or moist air under same pressure & temperature conditions'=n R T , PV=W/M*R*T : PM=W/V*R*T PM= density of gas *RT .At same pressure and temperature density of gas is directly proportional to average mass .If CO2 is introduced in place of H2O then density will increase.
19:51 - 23:39 When molar ratio of isotopes is given A+B in the ratio m:n molar ratio , then M avg =(m*M A+ n*MB)/(m+ n).M avg=Total mass/total moles and for a closed system ,Total mass is constant M avg is inversely proportional to total moles. There will be a rectangular hyperbola between M avg and total number of moles
23:40 - 25:04 A vessel contain equal mass of H2,He & CH4.Find M avg Solution :Let masses of H2,He and CH4 are W then number of moles will be W/2,W/4 and W/16 mol then M avg=(W+W+W)/(W/2+W/4+W/16)
25:05- 26:31 A vessel has 1 mol of O2 and 3 mol of SO3.Find M avg M avg=(1*32 + 3*80)/4 = 32+240/4 = 272/4 g/mol
This is the 3rd lecture in the mole concept chapter for class 11 Physical chemistry .It is very important for JEE Mains and Advanced .This lecture covers all the concepts of average atomic mass ,isotopes and relevant examples. This lecture is important for science students who are preparing for IIT JEE Mains and Advanced .This lecture has cleared all the basics of calculation of atomic masses
AVERAGE MOLAR MASS,
MOLE CONCEPT,
AVERAGE MOLAR MASS
ALK Sir,
MOLE CONCEPT ALK Sir,
Chemistry By ALK Sir,
IIT JEE Main and Advanced,

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[@anoushkapaliwal2854]

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[@krishnaupadhyay1057]

18:17 for understanding A 28.8g/mol substance replaced with 18g/mol substance so Mav will decrease

[@user-jk8ed9yh5w]

but why is it replaced?...shouldn't we add 18 to dry gas??

[@gokuGod0P]

Same doubt ​@@user-jk8ed9yh5w

[@vivekagrawal7746]

Poore KZbin pe ye concept isse accha nhi padhaya Experience speaks Thanks sir 😇😇😇😇😇😇

[@krishnaupadhyay1057]

18:12 for understanding If 10%O2 decrease and 10% h20 introduced then numerator decrease by 140 therefore Mav decrease

[@ReenaSingh-cr4ce]

The perfect teacher I find here❤️❤️

[@shikhasharma6795]

Great sir

[@Krishna.1829]

sir but how can we say that mavg is decreased in moist air. i didnt understood that part

[@adarshsengar6086]

Finally all concepts is Crystal clear thanks a lottttt my God

[@ruchimankar4336]

Thank you sir

[@anshumanrath9850]

best ever lecture on mole concept given by any teacher

[@abhijeetsinha3575]

NCERT + Your KZbin Videos + PYQs are sufficient to crack Jee Advanced ..

[@wolfiscrazy3179]

Nope you have to solve other books for jee

[@dream_alone]

thank you sir ❤❤❤❤

[@krishnaupadhyay1057]

19:20 if a gas lighter than Mav introduced in a mixture then Mav decrease so density decrease Vice versa also true

[@user-jk8ed9yh5w]

but why? if we add h20 the mass should increase right?

[@ReenaSingh-cr4ce]

This Channel diserve more than million subscribers

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in which IIT u are now ?

[@ritikraghuwanshi91]

SUFFERRED HARD @17:00 HOW Mavg reduces on introducing H2O and how dry air is denser than moist air ,,,,,,,CAN ANY ONE EXPLAIN

[@navneet4938]

Now For Mav of O2+N2 (20%,80%)=28.8g/mole. But after introducing H2O(molar mass = 18) the percentage of O2 and N2 will decrease. earlier it was 20%,80% but now it will decrease say 10%,(o2),70%(n2),20%(h2o). Mav now is around 26.5. As (density is directly prop to Mav) the density of moist gas is lesser now.

[@samridhi6459]

@@navneet4938 quite impressive, thanks

[@bhavyakhandelwal6566]

sir aap ne starting mein Mavg ko atomic mass kha than aapne dry air or moist air ko que. mein Mavg ko avg.molar atomic kha to thoda confusion h

[@mom_234]

17;55 solved the mystery of speed of sound in humid environment 👌👌👌👌👌👌👌👌👌👌👌

[@jeeaspirant9972]

For those who have doubt in the ques that why dry air is denser than moist air : The formula for % by mass of any component (A) = x × Ma/Mavg, now mavg = x × MA + (100-x)Mb / 100 now since another gas will be added in numerator so the value of Mavg will increase so now we know that dmixture is directly proportional to Mavg so the density will be higher. Btw if I am wrong then plz correct me as this is just my own theory

[@navneet4938]

one thing is that since n2 has such a high percentage along with a high molar mass(28) = 80*28 but now if u add h20 the perc of N2 decreases and also h20 has much lesser molar mass of 18. So now say if h20 added is 20% and n2 decreases to 60%, 60*28 + 18*20 < 80*28. (im ignoring o2 here )

[@Arch009]

@@navneet4938 even if you dont ignore o2 still ur argument holds buddy.. Ur correct!

[@krishnaupadhyay1057]

​@@navneet4938true

[@krishnaupadhyay1057]

​@@Arch009yes we could also remove 10% O2 and 10%N2 and add 20%H20 still the argument holds true

[@piyushmishra8416]

question practice kha se kre ?

[@garvitverma9282]

thank u sir

[@user-lr8ec6rl4l]

please get to the point quicker, like tell us what you are solving for or deriving before doing it so we have an idea

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Day-02 Target lec- 3,4,5,6

[@techuser7272]

24:34 common alk sir W

[@strifeisback4818]

sir ham average molar mass nikal rhe hai but ham har jagah , moles * molar mass kr rhe , usse to weight aajayega , molar mass thodi aayega

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Sir majaa aagaya aur dijiye

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Kya loge

[@adityavardhansharma1733]

Has sir earlier taught the concept of rectangular hyperbola?

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Good

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More than sufficient

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These videos r gem for jee students preparing for advanced too

[@thedevelopingpersonality291]

Sir moist air and dry air which is more denser wala concept samjh nhi aaya

[@gamerpanda8046]

Sir at 24:35 question why u didn't u multiply moles in numerator

[@aryanbudhiraja9906]

I also earlier had the same doubt but please watch carefully w here is taken as the given mass not the molar mass while in its next question 32 and 80 are molar masses that's why they are multiplied by respective moles as molarmass*moles=given mass

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Thanks!❤

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3 Done

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sir with your lectures and self practice can i clear JEE adv? pls tell i am new to this channel and in class 11

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Yeah it's sufficient

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sir aap aise pda rahein ki jaise hamein sab kuch pehle se hi ata hai please don't teach in brief

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love this type of teachers.......................................

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Great sir. U r legend of chemistry

[@abhayshukla5175]

Sir i have a doubt is there any condition that % by mole = % by mass

[@shounakghosh8595]

When M_A = M_av, that is, when there is only one gas in the mixture. Though I am pretty sure then it wouldn't be called a mixture

[@stranger1111]

24/1/2022-12:46 pm done

[@JEE2025Aspirant-co3sp]

Can anyone please tell me how sir took 100 in the denominator of total mass at 10:33

[@bhargavgahtori9499]

when we have a fraction in the denominator of a fraction say a/(p/q), we can get q to multiplication as the numerator. (basic math) so, sir just did it the other way round. you can try it yourself. hope this helps.

[@satyamthakur2]

He has assumed that there is 100 mole atom and then he continues

[@satyamthakur2]

How much syllabus have you covered yet?

[@himmedico]

✅

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it undoubtedly good lecture.

[@harshtomar101]

Bhaiya which gas will be more denser??H2O or CO2? Aap ek baar bta di jiye mujhe smajh nhi aaya

[@harshtomar101]

Bhaiya at 18:00 gas mixture of CO2 will be denser than dry air, right?

[@AadityaSingh-ln4tg]

@@harshtomar101 Yes.

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Will check

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5:00

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3:00 pm 12/12/2021

[@annie01736]

18:09 anyone please explain

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2/1/2022-done

[@nenadpanda2046]

Op

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Wdym by closed system?

[@user-qm3td5fh2u]

adiabatic system. in other words, there is no loss or gain of heat in any way.

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har 5 minute mein ad kyun laga rakhe hain, 10 m inute mein toh lagau, mohit tyagi sir ke toh ek bhi ad nahi

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sir ne ek ghante mein itna kara bhi diya

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Starting 26/07/2022

[@rohitkr9496]

13:05 a miscalculation sir

[@Arch009]

sahi hai bhai

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R these lectures gd for jee advanced? ?..plz tell...I am new here.....is this better than unacademy JEE channel?

[@sankomteam623]

same ques pls anyone reply

[@dilipdubey4421]

sir why you neglet co2 in question 17:04

[@Arch009]

amount of co2 is very less in the air thats why

[@Rituraj-ty4qw]

What is the difference between molar mass and molecular mass pls tell😭😭

[@ishansingh1545]

Molar mass -massof one mole of atom or molecule Molecular mass-the mass of a given molecule is known as molecular mass

[@JEE_Voyage]

(Molar mass and molecular mass has the same numerical value) Molecular mass is the mass of 1 molecule of any compound whereas molar mass is the mass of 1 mole atom/molecule of the substance

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continue tommorow from 6:09

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bhai abb continue krle

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Alok sir , please upload notes

[@MohitTyagi]

You have to make notes for yourself.

[@carryhaden7080]

Normality ????

[@wariskhan6643]

Hmm

[@destrobreakerz2957]

sir why average molar mass decreases on introducing lighter gas? thorasa or elaborate karke bataiye na please.

[@himanshuwadhwa4945]

Kunki same pressure pe H2O ko introduce kiya to 02 kr N2 ko km krna pdha jiska average mass jyaada h H20 se to moist air ka avg mass km ho gya

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Hello

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Molar and molal are absent in this playlist

[@rakuten_jbl]

Refer Solution and Colligative Properties and Equivalent Concept

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if u want to feel the topic ,,,dont study here,,go to moleconcept oneshot pankaj sir physics wallah ,,,otherwise u too will regret in the mid of chapter when your concepts will contrast

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Real Kings of Feejiks , Kemistory and meth in one place ;)

[@ramkishormahawar4509]

At 11:05 100 ko aise kaise niche le aaye

[@kingpatil2882]

Bhai agar aise niche laya to koi problem nahi he EG= (a/b)/(c/d)= (a/b)x(d/c)

[@omsai4976]

Kyu ki total % of mass of mixture 100 assume kar sakte hain isiliye upon mein total 100 aaya hai

[@Rishabh0Shukla]

Because: ( x × Ma + (100-x) × Mb = Mav × 100 ) Now, put this value in the equation of (% by mass of A) & you will get your answer!! 😀 Hope it helped...

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Jab tum yaha padhne aaye ho toh Bina matlab ke sir ki speaking mai kyu comment krra h?

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