17.3 pH Calculations Involving Titrations

[@ajax77123]

Love professors with these enthusiastic teaching methods. Helping you connect all dots.

[@ChadsPrep]

Much appreciated, Aj - thanks for the comment!

[@avrohomhousman5958]

Wow. My stupid textbook gives no instructions on how this is done so I spent forever trying to figure it out. I should've come here earlier. You are very helpful. Thank you

[@lekanganambela5183]

It doesn't makes sense how little exposure your videos get. You're literally so good at what you do.

[@ChadsPrep]

Thanks for saying so!

[@Eric-sq4hd]

god. man. thank you so much. so clear. got this in 3 minutes and 45 seconds

[@ChadsPrep]

Awesome Eric! You highlighted my two main goals: clarity and efficiency!

[@picklepickley591]

My exam is in 2 days and tbh binge watching your videos is the only thing that’s helping me clear up my doubts. Much love ! 💗

[@ChadsPrep]

Awesome Pickle! Hopefully you'll soon be in a position to binge watch something more entertaining than some chemistry videos.

[@RinaNewhouse]

The shortcut summary on your thumbnail was helpful!!! Thanks for helping me feel prepared for my exams and quizzes!

[@ChadsPrep]

Happy to help, Rina - glad you found the channel!

[@RinaNewhouse]

@@ChadsPrep You helped me ace the quiz!!! The cheat sheet helped!!!

[@ChadsPrep]

@@RinaNewhouse Great news, Rina - kudos to you for all your hard work.

[@RinaNewhouse]

@@ChadsPrep :)

[@issacepowell4850]

Tomorrow's the finals and I never knew how to do titrations properly. This video saved my life.

[@69Paulita]

Without a doubt, you are a terrific teacher. I appreciate the way you break down the problem to the smallest details. Thank you so much for sharing your knowledge with us.

[@ChadsPrep]

Thanks, Paula Leslie!

[@devikanair44]

this video honestly helped me so much. thank you so much for what you do, it really helps all of us. definitely explained better than some of the more well known resources. keep doing what you're doing!!

[@ChadsPrep]

Glad it helped Devika! And I'll definitely keep doing what I'm doing!

[@seekingrafael5630]

The type of teacher every student needs! :) thanks a lot. You seem like a very nice dude!

[@ChadsPrep]

Thanks! 😃

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Super grateful for these videos! We are very lucky to have access to this kind of information in this day and age

[@ChadsPrep]

Glad you are enjoying the videos, Omni-Kriss!

[@louinerdamicog377]

Having a quiz tomorrow, hope this help💖😭 thank youuu

[@ChadsPrep]

Good luck!!

[@andgeobaidoos8130]

You're a great teacher, you remind of my highschool teachers who made hard subjects fun

[@ChadsPrep]

That's great to hear - Happy Studying!

[@martinsikasote2839]

This is absolutely amazing, its the summary of the whole chapter calculations

[@ChadsPrep]

Glad you find it helpful, Martin.

[@Eric-sq4hd]

thank you. have been looking all over for this

[@adbycheri2853]

This was amazing! This all clicks now. Thank yoU!

[@salmam.s5540]

YOU ARE A LIFE SAVIOR ! THANK YOU !! 🤍🤍

[@ChadsPrep]

You are welcome, Salma - glad they are helpful!

[@lexichavez-l1e]

I was so lost, and this video connected SOOO many dots for me.

[@ChadsPrep]

Awesome!

[@stewste4316]

best titration explanation ever, great job

[@bigolrichkidz714]

Hello ! What are the 5 type of problems you mentioned when working on the weak acid equation? Thanks a lot for the video!

[@claireoliver3952]

Thanks, this is so helpful!

[@ChadsPrep]

You're welcome!

[@shivabayat8715]

Hi Chad. First, Thank you for your AMAZING explanation. I have a question: At 18:50 you find the concentration of F-. But in the shortcut formula, you mentioned that it is the INITIAL concentration of [F-]. I am a little bit confused, that we dont have the initial mole or volume of F-. Why do we use the final mole and volume of that in the formula Thank you

[@thatbossguy123]

Wow thank you so much for such a great explanation!

[@ChadsPrep]

Glad you found it helpful helpful! If for any reason you wanted a little more on this subject I wrote an article as a companion to this video that shows an example for every situation for all the standard types of titrations. You can check it out here: www.chadsprep.com/chads-general-chemistry-videos/titration-calculations/ Happy Studying!

[@luisapagliara5900]

Hi, could you explain why at 17.25, NaF is a weak base? I'm a bit confused as I thought that a weaker acid (HF) means a stronger conjugate base (NaF). I've watched your acidity and basicity of salts video but just can't seem to fully understand when talking about metal ions and anions. Thanks so much for your time, any help at all would be greatly appreciated!!

[@ChadsPrep]

Hello Luisa, so you've got it right when you say that a weaker acid means a stronger conjugate base. But the key here is that we are using the adjectives weaker and stronger, not weak and strong. It would not necessarily be true to say that a weak acid has a strong conjugate base...you must stick with weaker and stronger. For example, let's say we compare HF to HCN. HF is a stronger acid than HCN but they are both weak acids (neither is on the strong acid list). And if you compare F- to CN- you'll find that CN- is the stronger base, but they are both weak bases (neither is on the strong base list). The idea then is that for a conjugate acid to be a strong acid, the conjugate base doesn't just need to be any old weak base, but it has to be a super, super weak base (I like to call them 'negligible bases' in my video on salts. These 'negligible bases include Cl-, Br-, and I- and notice that the conjugate acids, HCl, HBr, and HI, are all strong acids. This is why I make the distinction between 'weak' bases and 'negligible' bases. The conjugate acid of a 'weak' base would still be a 'weak' acid (though a weaker weak base will have a stronger weak acid), and the conjugate acid of a 'negligible' base is a strong acid. Hope this helps!

[@luisapagliara5900]

Chad's Prep Perfect Thank you so much!!

[@jt21419]

In the last problem, for [OH-] you are taking the square root of moles/L. How do the units work out?

[@sahitihibane]

These videos are REALLY REALLY helpful! These just made my day because until now I was really confused with what was happening with all those different types of titrations. Thanks a lot again :D Also, you have been referring to 5 types of titration problems and shortcuts to solve them. Can you please list those types and shortcuts for those problems?

[@ChadsPrep]

Glad you found this helpful. I also embedded this video on this page (www.chadsprep.com/chads-general-chemistry-videos/titration-calculations/) and included diagrams and how to work out the pH calculations for every point on a titration curve. I'll also be sure to add a table to this page later today to include the 5 fundamental pH calculations (strong acid, strong base, weak acid, weak base, buffer) and how to perform those calculations quickly. Hope this helps!

[@sahitihibane]

@@ChadsPrep Thanks a lot again! That'd definitely help.

[@ChadsPrep]

Sahiti, I got busy doing other things, but just added the summary table to the page. Happy Studying!

[@sahitihibane]

@@ChadsPrep I'm sorry but I'm unable to find any table on the website :(

[@sumedharajput7013]

Hi :) Glad to watch such informative video. I need one suggestion related to my titration experiment of equimolar solution of both Methane sulfonic acid and Guanidine carbonate in water. I need to prepare salt (Guanidinium mesylate) after combining salt with the stoichiometric ratio determined by titration. For titration, i need to use pH meter at every step of adding some fixed amount of titrant (acid solution) I m unable to get stoichiometric ratio by doing titration process. Please suggest me over this. It would be a great help. Thanks

[@theopenacademy9102]

Amazing lecture!!! So concise and well done. sheesh

[@ChadsPrep]

Glad you liked it!

[@frannyfu650]

This was SO HELPFUL

[@ChadsPrep]

Glad to hear it - thanks for letting us know!

[@NirobPlays]

I'm from Bangladesh. I'm not in an English Medium School but still loving these videos soo much. Some words are hard to catch for me but I get those eventually afterwards.

[@ChadsPrep]

Keep up the hard work, Mehedi - it will pay off!

[@davislake5176]

Everything clicked during this video, I don’t know what did it, but thank you.

[@ChadsPrep]

You're welcome - glad to hear it!

[@CielINV]

Thank you this was broken down beautifully

[@ChadsPrep]

You're welcome and so glad you found it helpful! I actually intend to re-make the series next year and to cover this topic even a little more comprehensively! I show examples of all the possible calculations to go alongside this lesson here: www.chadsprep.com/chads-general-chemistry-videos/titration-calculations/ Hope this helps and Happy Studying!

[@coolkid9206]

Hey, how do you tell what the limiting reagent is in those 1:1 ratio reactions? Like in question 2

[@ChadsPrep]

Hey Cool Kid! In number 2 we have a strong acid and a strong base (HF and NaOH). As a short cut, if the concentrations of strong acid and strong base are equal the one with lower volume will be limiting reagent since it will give fewer moles of H+ or OH-, so NaOH in this case which only has 25ml compared with 100ml of HF. We did calculate the moles of each just to show you: 0.01 H+ vs 0.0025 OH- means we have 4x as many moles of H+ than OH-. Hope that helps :)

[@akshit6636]

Sir I have doubt in last question. Since there were NaF and H2O remained so it should be salt hydrolysis of anion here but you apply formula of weak base . Why ????

[@ChadsPrep]

Hey Akshit! If I'm understanding your question correctly are you thinking F- is a strong base? F- is our most electronegative element so it absolutely hates donating electrons, making it a weak base

[@josephsalazar5720]

Great teacher how do we see the five types of problems

[@ChadsPrep]

They are covered in chapter 16 and the first lesson of chapter 17. Strong Acids and Strong Bases: kzbin.info/www/bejne/jYbOmpSbj8qSadE Weak Acids and Weak Bases: kzbin.info/www/bejne/a3rPeZWZbL-La9k Buffers: kzbin.info/www/bejne/d4LHlqZohNF_nbc Hope this helps!

[@parwanalutfi8044]

Hi Chad! Just want to confirm: for half equivalence point buffer calculations, the molarities of the strong acid/base with the weak must be the same, but the volume must be double for the weak (2:1 ratio) in order to have pH=pKa correct? If the molarities aren't the same, I am assuming you have to write out the whole process? Thank you!!!!

[@ChadsPrep]

Yes Parwana. The idea is that you need roughly twice the number of moles of weak acid/base as strong base/acid. The most common ways to achieve this are 1) to use equal molarities but twice the volume of the weak acid/base as you suggest. 2) Or you could also use the same volumes but use a solution of the weak acid/base that has twice the molarity of the strong as well. Hope this helps!

[@ajimoko150]

Sir, if I may ask,why did we ignore Nacl in the first example and take NaF into account, even though Cl^-1 and F^-1 are both anions and they both form part of a solid.

[@ChadsPrep]

Good question Hellen - around 1:10 I say that NaCl is a negligible salt so it doesn't affect the pH of the solution and is ignored

[@rachelmanavi4819]

these are so helpful thank you so much

[@ChadsPrep]

Glad you find them helpful, Rachel!

[@vickyzesu]

🙌🙌🙌 lifesaver!!

[@ChadsPrep]

👍 👍 👍

[@BeingLifesBeauty]

Hi Chad, which video can I watch about the 5 shortcut equations that you mention in this video?

[@ChadsPrep]

I've organized this playlist as an embedded course on my site. First, check out the page corresponding to this lesson: www.chadsprep.com/chads-general-chemistry-videos/titration-calculations/ In addition to the embedded video you'll find lots of details including the summary of the 5 types of pH calculations you see in the thumbnail. But I cover the different pH calculation problems in some of the preceding lessons in this chapter (ch. 17) and in chapter 16. The 5 types are 1) Strong Acid, 2) Strong Base, 3) Weak Acid, 4) Weak Base and 5) Buffer. Strong acids and strong bases are covered in lesson 16.3 of this playlist. Weak acids and weak bases are covered in lesson 16.4. And Buffers are covered in lesson 17.1. Hope this helps and Happy Studying!

[@BeingLifesBeauty]

@@ChadsPrep Youre the best. Thank you so much!!

[@ChadsPrep]

You're welcome!

[@guadalupegonzalez7658]

you are godsent. TYSM

[@ChadsPrep]

You are welcome, Guadalupe - glad you find the videos helpful.

[@EuropeEduVoyagewithZ.S]

Awesome Sir

[@ChadsPrep]

Thank you

[@obenagboranyo7448]

Thank you so much!

[@ChadsPrep]

You're welcome!

[@leaafitch]

Seriously dude. thank you

[@ChadsPrep]

You're welcome!

[@peacealadejebi919]

I HAVE AN EXAM TMR MORNING AND I REAALY NEED AN ANSWER TO THIS QUESTION: WHAT DO I DO IF I DO NOT HAVE THE VALUE OF Ka IN A WA\SB. WILL IT EQUAL 1.8X10-5 IF NOT HOW DO I FIND THAT VALUE.

[@ChadsPrep]

To find the pH of a weak acid, you have to be given the Ka and the concentration (on homework they can expect you to look up the Ka value in a table in the back of the textbook, but on a test it will have to be provided). The alternative is that you could be provided with the acid concentration and the pH and then be asked to solve for the Ka instead. And then for titrations, if they want you to calculate the pH, once again you will need the Ka provided. But they could give you the pH at the half equivalence point (where pH=pKa) and ask for the Ka. Also worth noting, the videos on titrations in the more recent playlist are a little more thorough if you're looking for a little more clarity. kzbin.info/www/bejne/aYqchZSurMiEfdU Hope this helps and best wishes tomorrow!

[@civicstestandn-400applicat3]

I have my lab final in a week. I hope I do my best!!

[@ChadsPrep]

I hope you do well!

[@MaselaKubyana]

So sad to discover such an amazing lecturer rn 😭,but thank you for this lecture

[@ChadsPrep]

You're welcome

[@tanyaswartz9401]

You are amazing 😭

[@ChadsPrep]

Thanks TAnya! Glad you're finding my videos helpful! Especially titrations; they can be a pain in the butt!

[@Mahdi.the.better.doctor]

oh my god that was wonderful

[@ChadsPrep]

Excellent!

[@basilwilson3929]

How volume of HCL become 0.25L? Because in question it is 150mL.

[@ChadsPrep]

Hey Basil - when we add 100mL NaOH and 150mL HCl together their volumes combine which changes the concentration. So the new volume for both is 25mL = 0.25L

[@smhemant9111]

good lec sir, it really helps

[@ChadsPrep]

Glad you think so! Best in your studies!

[@natashaabrowne5258]

@chadprep thank you !!!!!!!!!!! So much

[@ChadsPrep]

You're very welcome Natashaa!🙂

[@alexsheremett3097]

awesome lectures thanks 1000 0000 times just unreal, unvaluable work (genius); but at 10: 23 instead of taking logarithm base 10 the student calculated using the natural logarithm; so log base 10 of 0.0025/0.0075 (= 0.477)is not equal -1 but log e (0.0025/0.0075 ) does, so the true value of pH is 3.7-0.477=3.22

[@Eric-sq4hd]

still confused on how to "find the pH at equivalence point" it is confusing because the number of moles should be the same...

[@Eric-sq4hd]

got it figured out though.

[@dulxbe4883]

yep, this is definitely *Chad's* prep

[@ChadsPrep]

Welcome, Dulxbe!

[@belaytesema7952]

You are special

[@ChadsPrep]

Thanks, Belay - I hope the material is helpful!

[@duncancarterii]

W teacher

[@ChadsPrep]

Thanks!

[@claireoliver3952]

What level is this teaching at? University / A level?

[@ChadsPrep]

They were presented for University students but I've had many high school students (such as AP or A level) using them too. Best!

[@matildawillcox1693]

Brill!

[@zieeeeeee1630]

He's Bald, He's a Chad But most importantly, he's a chemistry god

[@ChadsPrep]

Happy Studying!

[@sajjadanjum2695]

cool

[@ChadsPrep]

Glad you think so!

[@simpsimps553]

I think one of the pH answers had the wrong number of sig figs 🤔

[@ChadsPrep]

I'll have to go back and take a look but most gen chem courses don't teach students how to apply sig figs with logs (only multiplication/division or addition/subtraction) and I definitely didn't have it in mind in the least when filming this lesson. The rule says that the number of sig figs to the right of the decimal in a number when expressed properly in scientific notation should be the same number of sig figs right of the decimal after taking the log of the number (Ouch!). Because we don't typically teach this rule we either tell students to give the pH rounded to such and such a decimal place or don't specify at all for a multiple choice question where there is only one numerically correct answer. Thanks for the heads up and happy studying!🙂