pH and pOH: Crash Course Chemistry #30

In this episode, Hank goes over Reversible Reactions, the water dissociation constant, what pH and pOH actually mean, Acids, Bases, and Neutral Substances as well as the not-so-terrifying Logarithms, strong acids, weak acids, and how to calculate pH and pOH. Oh, and litmus paper!
Pssst... we made flashcards to help you review the content in this episode! Find them on the free Crash Course App!
Download it here for Apple Devices: apple.co/3d4eyZo
Download it here for Android Devices: bit.ly/2SrDulJ
--
Table of Contents
Reversible Reactions 3:40
Water Dissociation Constant 5:00
Acids, Bases, & Neutral Substances 6:38
Strong and Weak Acids 7:43
Logarithms 1:46
Calculating pH and pOH 8:45
Cool Mathematical Connections 9:54
Crash Course is on Patreon! You can support us directly by signing up at / crashcourse
Want to find Crash Course elsewhere on the internet?
Facebook - / youtubecrashcourse
Twitter - / thecrashcourse
Instagram - / thecrashcourse
CC Kids: / crashcoursekids

[@crashcourse]

Pssst... we made flashcards to help you review the content in this episode! Find them on the free Crash Course App! Download it here for Apple Devices: apple.co/3d4eyZo Download it here for Android Devices: bit.ly/2SrDulJ

[@sujaybelsare4743]

YAY

[@aldrindeleon8910]

Yay

[@anchitrao7374]

These videos are ridiculously well made

[@krishnagoli687]

Damn they'd be really helpful if they went just a bit more into detail but nonetheless amazing production quality

[@foxyred3216]

"p" is an old mathematical symbol for "-log of" hence: pH = -log[H^+] pOH = neglog[OH^-] pKa = -log[Ka] pKb = -log[Kb] Well, that's what my chemistry professor, Dr, J. Rogers, told me.

[@kristina1463]

THANK YOU

[@rhythmthukral7857]

Shut up

[@ScareSans]

@Rythm Thukral you misspelled "you're welcome" Edit: Jesus I'm an idiot, I meant you misspelled thank you

[@pollenbunal2101]

Arceus The God Pokemon Hahahahahhahahah

[@aigle_grincheux]

Francis Martinez definitely the most helpful thing I ever read Especially when I try to learn something about pH for the first time in my life thank you 💜💜

[@Spycyzygy]

My chemistry teacher described the water to hydronium and hydroxide as water being so bored that it reacts with itself

[@waltermitchel6266]

lol

[@hassankhansa8603]

+aung Oo ROFLLMAO

[@HonzukiNoGekokujou]

Rsaramallac Mine too!

[@lanhua216]

Rsaramallac e

[@RyanBucao]

Me

[@daiwikdhar6464]

For a second while he was explaining logs, I realized Hank has great potential to start: CRASH COURSE MATHEMATICS!!!! Anyone who wants Hank to explain Math plz hit a like!!!

[@nickracca1993]

"ok so now that you're terrified, I'm here to help" -hope someone told me that word earlier.

[@fluffy3355]

god i hate how chemistry has so much vocabulary

[@drew.k2385]

"As you can see, the logs turn out to be a mathematical shorthand that saves us from having to deal with very huge or very tiny numbers." That makes so much sense now. Why can't textbooks just tell it like it is?

[@IndeedJoe]

finals anyone?

[@Togerax]

You know it :D

[@RedMinorFilms]

Sadly my finals are way above the the stuff in this video

[@thatnonamedude]

hi Unfortunately, me too

[@felixwiedenmann8625]

Yep it got me too

[@Gravios74]

Pff, yes

[@MagicallyEmily]

I honestly understand chemistry better through these videos than I do through my actual college chemistry course. Thanks, Hank!

[@pilotmoyafan]

I'm still kinda screwed for the test tomorrow....

[@1nfo663]

did u pass

[@Tutti22]

Nameless lol

[@shaisblind]

lol, some guy replies 5 years ago, someone replies 5 days ago..😆

[@pcrd38]

Howd ya do man?

[@ctsvblk]

ShadowBIRD maybe he died.. like actually

[@MasterGus501]

Man, you're great at chemistry! Have you ever considered cooking crystal meth?

[@dreadxo4083]

Hankenburgh.

[@zombieblood1675]

Gus F breaking bad refrence. lol.

[@varshitakolipaka7933]

BREAKING BAD.

[@Telishahful]

most heard sentence of a chemist

[@happymolecule8894]

Cooking cocaine is much better

[@windowsxboxguy]

this the type of guy to help me pass my test tomorrow

[@SWEm4rt1n]

I love how this series is perfectly synced with my lessons in college so I can repeat my studies while I'm on youtube :D

[@jessjms1181]

Why is water so cute

[@jessjms1181]

Dan Vegas I don't remember why I said it to be honest

[@braveheart3847]

lol

[@dmoneyswagg64]

Dan Vegas why did I like this comment?

because it obeys you, molds to your every desire, because it's the girlfriend you'll never have because all you care about is yourself

[@chemistrychannel5021]

Because it's bent 😂

[@storyspren]

That pH + pOH = 14 is actually really cool, since it's a nice little shortcut you can take when you want to know either of them and know the other.

[@2357y1113]

Crash Course, thank you so much for believing in your audience and therefor not being afraid to show actual math(s) and formulas. You're the best!

[@PerryTheGangsta]

10:05. Was that a mistake on his part? The numbers he got from [H^+][OH^-] were 3.5 and 10.5 in the example he used. Thankfully it still equals 10^-14 in the end, though.

[@Sophie-wf3ex]

"...in the example we just did the pH was 5.4 and the pOH was 8.6" (10:02) erm... Wasn't it 3.5 and 10.5... Interesting editing.

[@jungsooneul8879]

I thought so too...

[@miav2046]

i caught that too and threw me off. kept rewinding thinking I missed something, at least our answers 3.5+10.5=14

[@arianasanchez4746]

Damn. I'll look for another video to study 😭😭

[@ScholaBayBee]

sameee

[@plazmavolt1238]

yeah...

[@josiahklein70]

Crash Course Mathematics, anyone?

[@basmetten7164]

ya

[@consavvy5754]

Yea

[@aperson3859]

Josiah Klein yes please

[@mystuffnthings23]

Yes, Please! He makes everything way more fun.

[@firozbakhtahmed4428]

Josiah Klein Yeees

[@Valdagast]

And the pH of blood should be between 7.35 and 7.45, _not_ (as I read on an alternative medicine site) 5 and 9.

[@khalidjaved5325]

It is 7.4 written in my book

[@itskankan]

That kanye power thing was the best thing I've seen on youtube this week! Keep up the creativity :)

[@Abominatrix650]

I'd just like to say that during the Kanye bit at the beginning, there's a Damocles Sword above his head. Thought we wouldn't notice. But we did.

[@meganyamamoto31]

4:40 H20 -> H30+ + OH- Not sure if anyone else has pointed this out but I don`t think this is balanced. It looks like a hybrid equation of H2O -> H+ + OH- and 2H20 -> H3O+ + 2OH- ?

[@JuiceCarver]

Thanks Hank! My teacher has been repeating the same material to us for 2 hours and nobody got it. Praise Hank for 10 minute crash courses!!

[@xXgracexX333]

My chem teacher is awful...she should honestly just show these videos!!! They help me so much to understand! Thank's Hank!!!!

[@riyasingh7287]

Can we have CrashCourse Physics? :/

[@kimberlyyeokahyii]

They alrdy have it but it's not Hank doing it

[@LA-rp5uy]

Riya Singh have you even searched it?

[@kripashankarshukla4073]

It is there, search it

[@fernandobaranano5032]

I come from the future, they've already done it, enjoy!

[@sumantrajkumar7372]

careful what you wish for

[@hazzacookiemofo]

I love all of the pop culture references in the show, like Deadmau5 when Hank was talking about Strong Bases

[@PartyChicken407]

Thank you guys so much for doing these videos. I'm not even a chemistry student, just a guy who was curious about world history (found the other crash course videos) and then I found these. Amazingly well put together and fun. I wish I knew what I know now back when I was taking high school science... I would have asked some really interesting questions and come up with some cool experiments.

[@BJB104]

Man, these vids helped me big time when taking chemistry in college nearly a decade ago. I work as a chemical technician in the semiconductor field nowadays, but rarely use theory and forgot quite a bit! Now watching again to give myself a little refresher for teaching my nephew with his high school classes. This is rad! Forgot how much I really liked this stuff..

[@f0gman_]

Thank you so much Hank! This crash course actually helps me a lot in school.

[@nelliesuto8007]

How great would it be if Crash Course created an Organic Chemistry playlist??? IT WOULD SAVE MY LIFE!

[@premgill2699]

10:00 The video makes a error Hal says the PH of the example we just did is 5.4 + 8.6 = 14. This is wrong. Actually, the PH of the example is 3.5 + 10.5 = 14.

[@veditababuta4201]

That' what I thought too, I watched the that part over 4 times to make sure.

[@DoctorSkater]

I already know every subject you have gone over in crash course chemistry. And yet I am nonetheless entertained by each and every one. You rock Hank :).

[@ScarecrowWoods]

i have no idea what im watching i think my brain is melting

[@andjeladzambas2874]

know how you felt....uffff

[@8ytan]

You neglected to mention, Hank, that kW is 1.0E-14 only at 25 degrees Celsius. At different temperatures, the value of kW is different and the pH of pure, neutral water also changes. I think (?) that this also affects the equation pH + pOH = 14 - I'm not 100% sure whether it does but I was always taught to be careful when finding pH from pOH using this method, instead we were taught to use a rearranged form of the kW equation.

[@krisxcross]

This helped me so much for my AP Chem class! We have to do a reading on this over the weekend and I didn't understand anything until I watched this video and also the acid-base reactions video! :D

[@19U91-l6s]

You save lives man!...🙌🏻🙌🏻

[@nmubunny5395]

Your videos are really helping me with my MCAT, thank you so much!!!

[@samanthalee36]

I'm glad I'm not the only one who feels the need to correct Crash Course chemistry videos. I haven't been watching in a while, so I had hoped they had gotten less sloppy.

[@allenhoggan7675]

Deadmau5 was the last thing I was expecting to see in Crash Course XD

[@justinhill6206]

to who ever matched the musical genres to the pH states you are a genius nice work

[@jeffshubert]

Great job Hank! It would be interesting to learn about the dissolving powers of really strong acids.

[@BlooregardQKazoo-ff6wb]

This is exactly what I am going through in school right now! This has really help me thanks.

[@jbkjbk1999]

English speakers trying to pronounce Ø, Æ and Å never gets old.

[@MrInsdor]

He does it pretty well though, ä ö and ü mostly get "ignored" and will be pronounced as a o and u : ^)

[@eliotoboyce5738]

+MankeyFrankie GöØd fØr ü

[@landonhillyard]

+Totally Not A Cylon Lived in Norway for 2 years. It took a bit for people to think I was from Norway, but eventually I got it.

[@IhaveCupcakes]

+Totally Not A Cylon I must agree

[@recklessroges]

Great video, (as always). What might confuse some people is that the word "base" is used in three different ways in this video: Chemistry: base as the opposite of an acid, Math: base 10 logarithms, and geek-cultural-reference: "All your base are belong to us" which refers to a military encampment. We just need to know who is on first to be really confused. "What pH does a log of base 10 have on your base?"

[@ScareSans]

"all your base are belong to us" i don't even remember where that's from, but i see it everywhere. for example, my younger bro was watching rescue bots, a transformers show for small children, and a character actually said that... it's everywhere

[@JonathanDery]

I just realised... I've been watching Crash Course since hte begining! Thanks for making me realise that, Hank!

[@neutralpresident4361]

My pH would be 7 because I'm neutral.

[@FROPDESAI]

Neutral President Neutral President is neutral.

[@darraghbrennan8549]

Neutral President ii

[@mihajlojovanovic7651]

Mine would be 14 cause I'm basic

[@tobey1684]

@@mihajlojovanovic7651 lol

[@mollyhorse]

@@mihajlojovanovic7651 and caustic! Lol

[@dragonbalism]

The opposite logarithm of the concentration of the H+ ion and OH- ion are inversely proportional, and this proportion makes the both of them add up to 15

[@bvbandiss]

These videos have helped me so much in my chemistry class. Thank you 😊😊😊

[@IllyaLeonovMorganFreepony]

Lower case p is used to represent a negative log of the hydronium ion concentration. The pH scale is logarithmic.

[@MegaMike327]

Universities should uses CrashCourse as it was way more interactive then Khan.

[@gwendance]

At 01:42 where it says that Hank is a mass of incandescent gas, is that a reference to the "Why the Sun Burns" by They Might Be Giants?

[@shannonbaker2254]

Senior Chemistry in Australia teaches you that pH stands for parts Hydrogen. Which in my opinion is probably the most logical way of looking at it. Even if it isn't historically accurate.

[@cutescience2109]

Delightful explanation of something we hear about all the time. I love that you start out by telling us that you are not "that into personal grooming!" Cute!

[@metadolle8925]

I thought the "p" came from the mathematical p, which stands for -(log). My chem teacher likes to tell us that to find pH or pOH from [H] or [OH] we have to "p on the concentration" -_- I will never, ever be able to look at pH scales without hearing him crow, "What do you do? You p on it!"

[@makeitmusical]

+Josie Serpan Strangely, this helped me.

[@metadolle8925]

Sarah Hudak Awesome, glad to hear it XD

[@h6ly]

well tbh p stands for power and H stands for hydrogen, im no scientist but pH is the power of Hydrogen

[@ScareSans]

@Jordan_acidic Hank himself said we could not confirm if pH means power of Hydrogen.

[@manimaima]

These videos are really helpful. You see I’m in year 10 and i really like chemistry. I’ve even started to learn AS chemistry. These vids make chemistry even more fun!

[@pri7974]

Wish my chem teacher taught half as good as Hank teaches. Btw Please bring crash course physics soon :))

[@Dixavd]

Yeah, I knew it would be something that would have to be true by definition. I was just impressed that there happened to be a model for giving the information of the H+ and OH- concentrations that aligned with using that fact so perfectly. I thought it was really neat that to represent this Chemistry information, they used this trick to make it so simple. Thanks for explaining though (I've always been bad at logarithms anyway).

[@abubakrakram6208]

0:43 It's just meant to signify "the power of"? I believe that's how my Chemistry teacher explained it to me. Of course, I'm not sure how much anyone would want to trust his explanation, considering I needed to go online to learn the material. I don't even know why I posted this comment; I'm quite sure Mr. Green knows his material far better than my Chemistry teacher. *EDIT:* He almost immediately says this is a possibility. I probably should have waited until the end to comment.

[@rithwiqnair537]

Helped me a lot.... Doing great Hank Green!

[@rex17ly62]

A common misconception is that a pH of 7 means a solution is neutral. This is just wrong, what makes a solution neutral is whether [H3O+] = [OH-]. For example, Kc of water at a temperature of 25 degrees is 10^-14, in which case [H3O+] would be 10^-7 and the pH would be 7. But in a temperature of 50 degrees Kc increases to 5.476x10^-14, and [H3O+] would be ~6.63. However, since [H3O+] = [OH-], it doesn't matter it is neutral.

[@david11559]

To ecsciguy79 If your solvent is already acidic or basic in nature then the concentration of H and OH will be different (ie it can't be neutral) The term acid and base still applies since for example ammonia will accept a proton to form NH4, hence it is a base. These terms needs to involve hydrogen, so since there is no hydrogen in liquid alloys or salt, it won't really apply.

[@thelark2049]

pH stands for: "potentia Hydrogenii" which is a newlatin word.

[@Qermaq]

I liked the cartoons in this one, especially Katherine pushing you around in the shopping cart. Do you two do that often? That looks like fun.

[@HarryBungholio]

Just want to say thank you for helping me understand chemistry. I wish you were my teacher. Or that I could just watch KZbin videos in my class rather than listen to a professor who cant explain anything. You rock. Thank you.

[@JoshuaLoganjoshuadlogan]

This is a great video series. Thank you for taking the time to make this!

[@boboloconow]

Thank goodness that I have CrashCourse to depend on before my exam

[@QUARTERMASTEREMI6]

+John Doe Absolutely! ;) Best resource ever made.

[@MD-nf5rr]

you're good at this man, keep it up!

[@shereitograce7844]

You explain chemistry so well. I feel I have won a higher level of knowledge

[@jonmorris2232]

Woah another channel with you...I NOW LOVE THIS CHANNEL

[@nicktimmerman8562]

0.5 speed and I couldn't stop crying

[@simonnance]

pHs less than 0 are fairly common. pH 0 would be 1M HCl or around 0.5M H2SO4 and up to 2M HCl (pH -0.3) or H2SO4 (aprox pH -0.6) are fairly common bench concentrations. 16M H2SO4 (aprox pH -1.5) is sometimes used in high school too.

[@000TheMatheus000]

here in brazil the p means potential, the potential of donating Hidrogen atoms.

[@kilroy3368]

That makes a lot of sense, I wonder why the rest of the world doesn't?

[@___xyz___]

come to brazil

[@rafaeljc12]

gibe money plox

[@chloegiraud2582]

+Kilroy 336 in Québec too it's potential

[@seantheguy1391]

You spelled hydrogen wrong

[@captainsmurk]

I'm such a huge fan of this guy and these videos! Awesome.

[@rachelgordon8330]

I was taught that pH came from French: pouvoir Hydrogene. Like, the ability to release the hydrogen ion and create hydronium ions...

[@Syntaxxed]

'so now that you're terrified" exactly my reaction when my teacher introduced pH and pOH without explaining us logarithms lol

[@Adnan-lt5rn]

I'm a simple man, I see Kanye Reference, I thumbs up.

[@serene9532]

@ 😂

[@kugelblitz7832]

These videos and Paul Anderson's videos on the Bozeman Science channel both compliment each other really well.

[@avazhalid7129]

The letters pH stand for the French words (pouvoir hydrogène), meaning "hydrogen power"

[@Latnii]

Thank you for this! I was in desperate need to understand pH and OH junk. Just in time as always, Hank!

[@TheRok]

Can't believe there are no high voted comments on “All your base are belong to us!” at 3:09! What, no gamers here? =)

[@whitebread7953]

thats a game thing? idk

[@talos111]

poorly translated Japanese game.

[@whitebread7953]

watts the name?

[@IntenseNoobFPS]

zero wing

[@whitebread7953]

k thx, i google now

[@babycash08]

I literally almost had a mental break down in class yesterday. Today I find this goldmine! Life is really good LOL

[@TheMisleduser]

can't lie. I should have been watching these instead of reading the text

[@Froggeh92]

Yes. the pH lets you know how Acidic/Basic your product is. The more balanced the formula the more gentle it is on your skin/hair and is friendlier for daily use.

[@johndou423]

Kw is only 1.0*10^-14 at 25 degrees celsius tho

[@jessicajohnson3986]

Chem regents tomorrow, and even though I know we don't need to know too much about this stuff in depth, I started freaking out. I know I can count on CrashCourse to relieve my sudden, absurd lack of knowledge :)

[@yousef.al-assaf]

What?! lol. The numbers that you got from your example were 3.5 (pH) and 10.5 (pOH), which their sum is also 14. Late night video, eh!

[@ingenuinegalaxies9299]

+Yousef Al-A'ssaf Did you watch the whole video? There is a reason for this. It is why we define a neutral ph 7.

[@stevenn2382]

Thank you so much! We went over this in chem and I thought I knew it well but this explanation helped me much more!

[@PinkLove961]

pH and pOH stand for potency (p) of hyrdogen, (H) and potency (p) of hydroxide (OH), according to my chemistry teacher with a phD. (

[@Dixavd]

They always add up to 14. That's really clever. I'm honestly impressed with the mathematics there (it's almost as if a mathematician derived it).

[@linguaphilly]

Haha that 'ohhhh'-moment at 6:28

[@TushitDesai]

ultimate presentation

[@LuisAntonio-xp4ep]

Pls guys, CrashCourse Physics! plsssss!

[@FouquetJulien]

i suscribed a few weeks ago and i was thinking to my self two days ago, I wonder how exactly acidity/base works on the molecular level. then BAM you show up in my inbox answering exactly what i was wondering. please continue to spy on my brain and answer my questions :D

[@user-em4rk4qo1f]

I have to watch these at 0,5 speed in order to understand them properly

[@EmmyKhan]

Ah good idea

[@noahwhetstone3525]

this may sound crazy but try listening at 2speed. it forces you to really pay attention if you want to understand what is going on and you (might) learn it better.

[@sherazkhan2802]

Ihate Mr. Wires How can I slow down the speed on a smartphone ?

[@_ashyou]

Sheraz Khan No you can't

[@Benny_Blue]

I watch them at 1.25 speed, so I can study more quickly.

[@cmtrocks330]

THANK YOU FOR POSTING THIS THREE DAYS BEFORE MY pH AND pOH TEST

[@alecogilvie8997]

Need to make sure that the effect of temperature on Kw is mentioned and that Kw is only 1 x10-14 at 25C, therefore, the pH of pure water is not 7 at different temperatures, but this does not make it acidic or alkaline as [OH-} =[H+]

[@mikeazevedo1613]

Well, I can help you with one thing. Although I saw one reference to pH standing for "Potential Hydrogen", what I was taught long ago makes a lot more sense. That it stands for Particles of Hydrogen, which is reasonable given that it's particles of the Hydrogen atom that are causing the pH to change.