GOOD LUCK ON THE EXAM EVERYONE

@maisoonpharmad3320

7 жыл бұрын

Rae Amiiiin

why is it, that youtube is now better than any of my chemistry teachers in my entire education history (1st school through to undergraduate)? Great videos mate...

@Brendanfarr29

8 жыл бұрын

+EvelcyclopS education system is trying their hardest, sorry it's not good enough for you.

You always save our asses. Thank you.

What you're doing for the education of the world is so great. You deserve a universal medal!

love your videos, i always search khan academy for chemistry and biology questions i have. Thank you so much

Thank you so much! Good luck to everyone who is having exam tomorrow

This has been breathtakingly helpful, thank you for uploading!

It's worthy to note that for the buffer to actual "work," you need significant amounts of the weak acid/base and its conjugate. So if you're adding a large amount of HCl to a buffer with small amounts of the buffering components (ie a weak base/acid with it's conj salt), the pH will change significantly.

You make pure gold, easy-digestible gold. Really, my chemistry book makes my head-ache while this easy to digest even while tired

I never knew buffers can be learnt without wanting to stop. I thank you Sal, for helping us helpless students.

All i need is a text book and this mans tutorials, then i'll be an A+ student.

Awesome. Your explanation at the end was done well, too. I was wondering about that in class today and you cleared my doubts.

Thumbs up to your videos! Not even my chemistry lecturers explain the way you do. :)

I was actually looking for a solution for internet buffer lol

@CharTiger

9 жыл бұрын

Same😂😂

@imalazykid the OH- is a strong base meaning it is far more likely to react with that instead of the A-

Suddenly Chemics is getting interesting to me

@stretchyrubberbands It won't go down because water will dissociate to form H+.. and it won't go up because it's also forming OH-... I think...

Water will add H+ and OH- ions, which will use up part of the buffering capacity. This means that when an acid or base is added, there is less capability for the buffer to act.

Ikr, his videos make me do that. And that too chemistry! can't stop!

i cant thank you enough! literally saved my academic life.

i don't really remember any of the log laws, but there's a negative sign in front of the log (xy). so if log (xy) = log x + log y then -log (xy) = log x - log y

you have NOOOO idea how much i love you.

KHAAAAAN! gread videos. Very usefull, and they are a big help in my studying for my may IB exams..

@7:30, sal mentions that the proton from HCl would react with OH- and neutralizes the reaction. And then, the reaction shifts to the right to make up for lost Hydroxide (OH-) ions. I get that. But isn't there a chance that same proton can also react with the A- too instead of OH-? And lets say, it did react with the A-, then according to Le chatelier's principle, wouldn't the reaction shift to the right, creating more OH- and thus increasing the pH?

thank you soo much! great overview, just what I needed!

Hi everyone! I have been looking around the internet for articles discussing how much buffer to add into a solution but all I've found are calculations on buffer preparation. I am preparing an antibiotic solution (synthetic antibiotic-contaminated wastewater) which will be treated afterwards at constant pH. I will be adding NaOH and H2SO4 for the initial pH adjustments, then phosphate buffers to maintain the set pH. My problem is, I have no idea how much of the NaOH, H2SO4, and buffer will I add to my solution. Could you please help me with this? I'd really, really appreciate it. Thank you very much!

5 stars are getting played out so I feel like coming over there and high fiveing you. THANK YOU!

this is helping me pass chemistry. THANK YOU!!!

Thx helps me for my upcoming physical chemistry lab

you don't know how much I love you

thanksz for the video...it relived my concept of buffer :)

I got a question!! Aint the conjugate base of a weak acid strong??? not weak??

"Straight up water" awesome :)

Wait so when equilibrium is reastiblished H+ will increase because of water right?

Thank you very much you really saved my life ..

Personally, I think his voice is quite enjoyable.

Oh, my God. This guy is SO funny!! :')

Its really helpful.. thanks ^.^

it is getting helpful for me

you saved my life.. thank you

OK as useful as that was for understanding, some of the words used wouldn't be awarded marks , especially with my exam board. They want you to say a buffer is a solution that minimizes or resists changes in pH. The mark scheme says you need a series of equations which you demonstrated well. And also to say what happens when you add an acid ( [H+] increases reacts with negatively charged base from acid dissociation. Etc. After doing a few questions its more clear what they are after.

why does the buffer capability decreases as the buffer solution is diluted with water

Really? You can make an acid with ammonium ion?

@overtonwindowsill5218

6 жыл бұрын

FortNikitaBullion yah

17:21 pH goes UP not DOWN

Chem final today... Wish me luck!

@StarShooting03

8 жыл бұрын

+James Ward good luck!

NaOH isn't a molecule Khan. It's an ionic compound. Molecules are typically held together by covalent bonds.

@claytonchristudass161

7 жыл бұрын

Artiom Gretsky face palm

hey buddy u told that because of NaoH the H+ get disapeared and the HA wl dissociate to undo the loss of hydrogen ,but my question is, what about the A ? IT GOES ON INCREASING and it should under go backward rxn to balance the A .then y doesnt it do a bkward rxn?

As true as that may be, you may want to watch more of "there" videos on grammar.

khan academy, you might just save my life

Love your videos, I am learning much in my retirement years. But simply dropping the units m/L from Ka at time 10:35 bothered me and since I don't believe log of a dimensional quantity is mathematically defined, I attempted to see if I could derive the H-H equation without violating mathematics or at least within some more explicit definitions. Here is the math: for compactness of notation: - anything inside [ ] is in m/L (moles/liter). - if a variable or constant is not inside [ ] then it is dimensionless, unless otherwise explicitly noted. - I drop the ionic charges. Your initial equation for equilibrium constant at 10:35 should have been written [Ka] * [HA]/[A] = [H] Note units on left and right side of my equation match, where yours do not at time 10:35 Now to get rid of the dimensions m/L from Ka so that we can take the log of it: multiply both sides by L/m Ka * [HA]/[A] = H take the -log of both sides: pKa - log([HA]/[A]) = -log H To get pH as defined within the Chem community we need to get back the dimensions for H by multiplying by m/L. This is equivalent to adding the log of m/L, then of course doing it on both sides of the eq. pKa - log([HA]/[A]) + log(m/L) = -log(H) + log(m/L) = -log[H] ...... -log[H]=pH by definition only. Then since pH is dimensionless and pH = -log(H * 1m/L) = -log(H)+log(1m/L), by definition log(1m/L) must=0 so... pKa - log([HA]/[A]) = pH or pKa + log( [A]/[HA] ) = pH since [HA]/[A] is dimensionless we get the H-H equation balanced with all terms dimensionless So only by defining log(m/L)=0 the H-H equation can be derived without erroneous math.... at least to my satisfaction.

@GrayGhosting

8 жыл бұрын

The mathematical reason your "amazing" conclusion at the end of the video was wrong is that a log of a dimensional quantity is undefined. So the log(moles/moles) is undefined and therefore you can not interpret that equation to say that the ph is independent of volume and only dependent on the ratio of moles of constituents. To be defined you need to remove the dimensions, i.e. divide m/L by m/L. This leaves no opportunity for the faulty interpretation. Or if one followed my math above one would see this equation.. pKa + log( [A]/[HA] ) = pH ... is only correct if Log(m/L) = 0, and this can only be correct if m/L is dimensionless. After consideration one can see it is in fact dimensionless when we realize that Liters are just acting as a scale factor for moles. That is to say, for example, we could write the very first equation with the ratio of atoms of H to atoms of H2O, which give a dimensionless ratio instead of the dimension of moles to liters. Following that approach throughout there would have been no opportunity in the last equation to remove the dimension of volume.

this could have helped as review before my final exam...

you have a sexy voice...it's nice to have it in memory when not stalling on my finals..thanx so much

React with the hydrogen and eat it all up! React with the hydrogen and eat it all up!

Thanks!

i guess Sal's good at explaining concepts but i wish he would solve some more complicated questions...maybe University style questions

Actually the dilution won't affect the ''log'' term (a part which you got right but again you got wrong in the mid video comment) but instead it will affect the pka of the solution.

thank you

thanks

this movie saved me 4 lessons chemistry _o_

dude totally !

thank you very much

thanks KHAN

AP Chem Test tomorrow. Lets Go!!!

go to 13:04 -log(xy) = - log(x) - log(y)

I wish to meet u one day

makes sense to me

Me too! Haha good luck

now i understand what buffer is...... one day before ap exam..... haha........

thank you soooooooo much

you know when you have the log (ha/a) is that not just log(ha) - log(a), could you write it that way?

This is the 2022 comment you’ve been looking for 😅🥰

MMmmmmm..so khan is 30 years old.....

@shubhbisht9363

6 жыл бұрын

42 in real life

thx

ur awesome

thanks a lot u explain it very well (Y)

Thats why youre watching the vid

Thank you for explaining to me WHYYYYYY!!!!!!!!! ahhhhhhhhh SO FRICKEN HAPPY!!!! HHAHAHAHHA

i love you thank you.!!!

I get it now

i have it in 1.5 hours....cramming

my teacher told me to take the day off and relax for the ap test tomorrow. well I guess that's not happening.

That statement at end is only true if the chemical is in excess.

@overtonwindowsill5218

6 жыл бұрын

Oh right he addressed it

ok WTF i go to the website and dont see this video under his playlist for chemistry

Yes I KHAN! :)

you too?!?! haha khanacademy all nightt!!

Sal the god!

Khan-jugates !

@africanchicaful WORD! Dude I read the chapter 3 times and thought a buffer was a vitamin supplement. After this video? I tell the exam......come at me bro! but please no hard questions

Can U put Arabic translation pls 😊..

@habeebhabib3160

5 жыл бұрын

ههههههههههههه

my final is thursday!! hahahahha!!

Comment on the edit at the end: wrong again. Initially, the math was correct (getting rid of the volume), but its interpretation was wrong... and the whole math thing was useless/needless anyway. The edit (the comments) were wrong.... when trying to discredit the 'correct' math with the example of diluting the solution with H2O - of course the pH will change due to Chatelier's principle. Your initial equation relating pH, pKa, and number of moles, is correct and APPLIES only at a particular instant/concentrations.

@Usman9217119

7 жыл бұрын

kris nika he is not gonna reply because the video post on 2009

@thelearner3962

6 жыл бұрын

The case in which adding infinitely excess water violates the assumptions made during derivation of HH equation, that's why we won't use HH for that case. That's all :p

UT CHEMISTRY TODAY. #RPLIFE HAHAHAH

3 teachers lost there jobs in the making of this video.

there no such thing as a ph 0 btw

Vitsmin supplement??? lmfao!! :P

oh you kids...lol

Well, if you intend to criticise my grammar at least master it yourself. I made a slight error in spelling, you made 2 immediately obvious grammatical errors in that sentence alone.

Didn't he make a mistake by using log instead of lg. There's a big difference ...

@melrakan

9 жыл бұрын

+dtoxwOw It doesn't matter. Since this form of calculations only uses the base logarithm, lg and log are interchangeable.

ACKWEEUS

Déjà vu ! o.O :D