Hess's Law and Reaction Enthalpy Change

[nhargravealton]

You my friend, are a life saver. I have A Level Chemistry coursework tomorrow afternoon and all I know is it's on enthalpy changes....which I knew hardly ANYTHING about before this. I couldn't sleep last night because I was worried I wasn't going to understand it. This video has helped so much. Thanks enternally :)

[aggceed719]

Wow, I was so confused in Chem lecture today :D but voila! I totally get this now! Time to do the giddy dance thanks to you!! :)) thanks!!!

[wc7vdaner]

U make me regain my confidence in understanding this.... tear*

[nishy0895]

Thanks so much! exam next week and just learnt something :D

[CasualGarbage]

Propane and Propane accessories

[farloo100]

You should apply for a job as a professor of chemistry at UCONN. i;d greatly appreciate it

[Jplaxtwo]

this was REALLY helpful i have been studying this for two hours and didn't get it then in 15min i completely understand thank you!

[1ronshy]

Thou is a Genious

[SkittlezGirl225]

THANK YOU GOOD SIR

[rahrahritaa]

back to this video.

i bombed this last test because my professor drops the lowest grade and i already did well on the other ones, but the final is next week!!! need to understand this video.

[rahrahritaa]

lol wow.. took me forever to realize that my professor uses C instead of Hf.. things are starting to clear up now.

[Nathproductions]

@rahrahritaa If he is using Hc that means it is the enthalpy of combustion

[kutecurse6060]

I want to meet u :( u are sucha genius! :o

[yankees5271]

I signed up on youtube just to say that you are AMAZING!!!!!!! Everything could be sooooooooo simple if the teachers just taught like you.

[thafua]

This was so helpful! Thank you soo much! I've been struggling with Thermochemistry and now I feel much more confident!

[denzelXlala]

I discover this too late!!!! my final is on tmr!! T.T help~~~

[eminemcr9]

OMG SAL WE HAVE THE SAME CALCULATOR!!!!:D

[LilLilSpinner]

My teacher did the exact same propane problem today and didn't make anywhere near as much sense. Thank you!

[TheNumber2Pencil546]

your voice is interesting...but at the same time soothing haha

[Asfina76]

Thank youuuuuu :)

[ThebirdmanTrainer]

This made this so much easier, Holy shit!

[pikachugirl666]

Why can't you be my chemistry teacher? TT__TT

[twilightsagasuperfan]

Thank you!!

[tcarp77]

i would thoroughly enjoy shaking your hand my good sir.

[CescFaBilal14]

fack u

[Hellgoregaming]

The best part of his videos is the fact that they're videos, pause, replay etc, etc.

[mafiaSage105]

this video makes my life easier, thank you mr. khan

[NuTaCinema]

cccccccccccrrrrrrrrrrrrrrrrrrr­rraaaaaaaaaaaaaaaaappppppppppp­pppppppppp :)

[DanceIsPassion411]

Oh my goodness, it feels as though the world all makes sense! Thank you so much for helping me out with Chemistry! If I ever get stuck again, I will definitely come back to watch more of your videos.

[dilanjanf]

Thank you so much Dr. Khan :-)

[jamiethaigirl123]

Thank you so much, Dr. Khan! You explained it a lot better than my teacher.

[Ibahz]

thank you dr. khan. you make learning fun

[SuperGuest69]

seriously, im takin chem at a community college, and the way u teach this is waaaaay better then how my professor does

[erin210992]

fuk u sal

[erin210992]

khan academy is shit compared to genchem

[KingZuluKing]

very nice video thanks

[Ariccio123]

My Chemistry final is tomorrow.

I have learned more in watching Khan academy for the past 2 hours than I have learned in an entire year of class.

--Speechless--

[22putu2]

Chemistry exams in 22 hours and i couldn't figure shit out of this until i came across your video, what a relief....thank you Mr Khan :)

[surfer3595]

Mr. Khan, Saying you videos are helpful would be an understatement. The only thing I would like to see more, which you do in some videos, is a brief overview of the general steps/equations used. I find this extremely helpful especially in the longer videos that have a lot of content. Keep it up!!!!

[nawalasif786]

thanks man great explanation! looks like i dont have to fail chem this year! :)

[nawalasif786]

thanks man great explanation! looks like i dont have to fail chem this year! :)

[iambarbie1234]

you are amazing!

thank you so much

[drspecial757]

My exam is in 45 minutes, I fucking love you

[shatzE3]

but i believe there is a mistake on the calculation part :

(3 x -393.5) + (4 x 285.53) = -37.2 ??

[RockNLoad07]

@shatzE3 Rewatch it and listen to him carefully, Water is - 285.53, his - and 2 just combined so it looks like plus.

Easy mistake to make though if you didn't hear him or watch him pick it off the list.

[shatzE3]

but i believe there is a mistake on the calculation part :

(3 x -393.5) + (4 x 285.53) = -37.2 ??

[shatzE3]

THANK YOU SO MUCH!! u finally cleared my confusion. I go to the (currently) 4th best skl in the UK nd my chem teacher is still could get this through my head but u done it 15mins lool

[sosburn24]

You may have just saved my life! Thank you!

I haven't been sure how to even begin studying but this has helped

[sosburn24]

You may have just saved my life! Thank you!

[owatonna06]

thank you again u the best.....

[PenguinMan272]

3 people found khan academy after failing their chemistry test hahaha

[rachelyelv]

You've essentially been my chemistry teacher this year.

Thanks(:

[MistaHuber]

How does one dislike his videos?

[RikuPrower]

Thank you so much for this! You really picked up the slack where my chem teacher was rather lacking.

[Elfflames]

good job explaining

[stev019]

Your video confirms that I know what I'm doing. Thank you =)

[highoctaneman2]

Test tomorrow! You made all of my studying make sense. It's all clear now. :)

[alexmotaf]

Amazing lesson!! I was strugling with that all night until i saw your video! thank very much!

[mashafasha5]

You just made my whole semester of chemistry obsolete. I thank you for that.

[willhelm87miles]

Sal what's your IQ, like seriously?

another great video THX!!!

[EpikkSwagg]

Thank you sooo much for your wonderful videos, you are a great teacher

[1GirlWith1Mission]

I find it funny when you say "I hope that was helpful". That 15 minute video was singlehandedly 10 times more helpful than a whole week's worth of 1hour long lessons from my chemistry teacher. 

[75zk]

Khan! Thank you so much, you are best teacher ever.

[05alis]

Ugh didn't help at all

[SapphireEmeralds]

One of my chemistry teachers spent 2 weeks trying to explain that to me, and pretty much failed-- and this video simplified it WAY more than he did.It makes sense now! Thankyou.

[SPRIIKO]

You sir, are better than my disgusting Chemistry teachers. Kudos to you.

[rushitelj]

@SPRIIKO if he was your teacher u would be saying same thing on other youtube video.

[DarkWhisper07]

@rushitelj you have no reason for saying so.....

[rushitelj]

@DarkWhisper07 yes , cuz all of us are same . he can'nt learn in class as much as he can learn while actually listening it to it 100% and in room ALONE by himself 

[SPRIIKO]

@rushitelj No...really no :L I can simply tell by the way he's describing it that he's so much better...

[snnacho]

I did find that helpful. Thanks Sal.

[knine178]

thank you so much :D much more confident now...

[lakersfanfor3va]

awesome vid

[TheDGFproductions]

ENDOthermic, heat is ENTERing

EXOtherimic, heat is EXITing

[Pablothe]

10:30 the table u used has liquid propane, in the reaction u used gas.

[snnacho]

@Pablothe you should probably make a video showing everyone how to do Thermochemistry now...

[Pablothe]

@snnacho lol

[polos505]

This is suppose to be a review for me. My professor failed to explain this in class, this is why I'm here. Anyway, Khan makes this stuff looks super easy, he is a great professor.

[dude2733]

in the second example u used the heat of formation of propane (liquid) but u had propane (gas)?? soo i wondered if that was just a typo

[LiveLoveLaff20]

you are my second ap chem teacher!

[teamindia87]

Thanxx

[carazycutiekim]

ok dumb question :/ so how do i determine endorthermic and exothermic?! i played it like 6 times maybe a written explanation will help!!

[ichinarukurumaki]

@carazycutiekim if delta h (enthalpy) is positive, then work was added. Therefore it is endothermic

[polos505]

@carazycutiekim

Look at change in H, Negative=exothermic, positive =endothermic.

[SuperTajman]

For the combustion of propane you would get water vapor, your state on the water should be gas.

[aarchana4]

Many thanks for this video. It was really helpful. :)

[Credge11]

I LOVE YOU!

Thanks for posting this, none of my teachers were close!

[DOSKOIxPITA]

great! thank you for the valuable knowledge!!!

[susielharris]

Omg thank you so much. This actually made sense to me.

[kayathon]

now i totally get it, thankyou so much :)

[Anoshh50]

you are a legend !!!!

[judgeomega]

You refer in several videos to the "Standard enthalpy change of formation" table and the entropy tables. But if you have to reference such a chart, why not just reference a chart with the answer to whatever you are trying to figure out? It seems like a very cheap way of doing things. What do you do when your dealing with an exotic molecule where you cannot find a reference? How are those tables derived? Is there a mathematical way to derive those values for yourself?

[mufc4everch]

@judgeomega These videos are made so that these relatively simple concepts (senior high school) can be understood by the students

If the students don't have to do these tables (and we do get them on tests/quiz's) then what would be the point of showing how those tables are made (other than confusing people)

[hisyamuddinistari]

OMG! Dude u rock man. I didnt understand a thing during my lecture earlier. After watching i understand now. Thanks to you. You should be a professor:)

[Kalamakooya1989]

Really good thanks :D

[jafarijoon]

u r the shit! Thanks a lot.

[TiZzZMeEe]

DUDE MARRY ME!!!! Incredible!

[kdcando]

The rest of the info is great, Thank you for making such helpful videos! I hope this clears things up, perhaps you can do an edit so the wrong information is not given any more.

Summary kids - the way to CORRECTLY ENTER THIS IN YOUR CALCULATOR SO YOU WILL NEVER FAIL IS: ((mol. x heat of formation for C) + (mol. x heat of formation for D))-((mol. x heat of formation for A)+(mol. x heat of formation for B)) you WILL need all those brackets on some questions!!

[kdcando]

Let's use the example of A + B yields C + D. 4 x 100 for molecule C + 3 x 200 for molecule D (assuming 4 moles of C and 3 of D, with heats of formation being 100 & 200 respectively) MUST BE ENTERED AS 4x100+(3x200). otherwise you end up multiplying 403 by 200, instead of adding 4mol of C and 3mol of D. Your calculator does equations in order left-right not order of operations, your answers will be incorrect if you do not use brackets! the same goes with Molecules A + B.

[kdcando]

IMPORTANT! PLEASE READ!!!!!!!!!\/\/\/\/\/\/\/\/\­/\/\/\/\/\/\/

Great Chemistry help but the math is off! When adding two products, which is what you must do here to add molxheat of formation of each molecule>

[Trogiss]

YOU ARE MY HERO

[YdLeet]

Thanks a lot. (:

[GraceKi92]

Where have you been all my life

GREAT explanation.. i understood first time round.

[ditchdigger126]

great explanation!! I should start skipping my chem class and watching youtube teaching videos instead, I would probably learn more. Thanks for the video!

[Jazz3940]

omg i wish you were my chemistry teacher! mine is horrible!!

[spiderdude423]

if it was not for you this semester i would be failing college chemistry, keep up the good work sir

[mKofiT]

Awesome!!! why do i pay a tutor $20 bucks and hour again???

[tybeany88]

seriously.. what the hell would i do without you????

[VideoCentrealChannel]

THANK YOU FUCKING GOD!!!!!

screw the educational system

this guy is the all the school u need!

[SteroidsR4success]

Wow this is just so good it's godly. After being introduced to the notions of "Enthalpy" and "Heat of Formation" from your last two videos, this video was so good that after I watched it I just instantly understood those two topics. I don't know how you do it Sal, but keep it up, you are fucking amazing!

[angrymuffins123]

thanks! helped a lot

[imin5thgrade]

thanks mr. sal

ur the best

indian pride!

[zramdeen]

u da BOSS ... i was absent the day my teacher taught this.. ty for explaning

[drstingrae]

2 Questions 10:15

Does this mean that both Water and Ammonia, being negative are instaneous in formation.

And also that even though water is formed collectively stable in this reaction, we still need heat to form NO, because Ammonia is also stable!

[zackcyboy]

a little long..but i knew most of the stuff. But 15 min...mehh.

[empress1993]

thankyou x

[jaideepsinghkapur]

@zackcyboy

fuk u, i want to see u do any better.

[BlackMetalWarewolf]

sweet. thanks for the help. i think i got this stuff down.

[Sasha7amad]

Loved this!!!

[zixerqwert]

The last part you made it slightly unscientific. If you have 33g of propane you use n=M/(Ar or Mr) this gives you say 0.09393, to find one mole, divide the heat given out buy this number to find one mole of propane.

[jeestudent007]

great!! eXplanation

[flipski909]

very nice video, but it makes it sound like you have to add up the reverse enthalpies for the reactants. At least that is what I got out of it

[EYEMJR08]

awesome video! got an exam over this stuff tomorrow and this really helped ;)

[dianelly]

thanks for the video

[carlkazuma]

Thanks!, Very helpful!

[luciieelue]

thank you so much .. i didnt get this and thanks to this video i understand it so much better .. thats again... really helps :)

[Teddex100]

Thank You So Much =D

[Mejiera12]

Thank you so much. This was extremely helpful.

[TTroti]

Thank you!

You are very helpful and clear, this is better then college :]

[hatoom1]

Does any one know who this teacher is? wow, why can't all teachers just explain it like this,

Thank you sir.

[KingMex32]

Thank you thank you thank you, this helped me out sooo much =D

[desi12693]

excellent work you're doing... congrats on all your success...

[doesthismakesense123]

niice