– [Voiceover] Let’s do

another titration problem, and once again, our goal is to find the concentration

of an acidic solution. So we have 20.0 milliliters

of HCl, and this time, instead of using sodium

hydroxide, we’re going to use barium hydroxide, and it

takes 27.4 milliliters of a 0.0154 molar solution

of barium hydroxide to completely neutralize

the acid that’s present. All right, so let’s

start with what we know. We know the concentration

of barium hydroxide. It’s 0.0154 molar, and we also know that molarity is equal to moles over liters. All right, so we have 0.0154 as equal to, let’s make moles X, over liters. 27.4 milliliters is 0.0274 liters, right? So that’s 0.0274 liters. We solve for X, and X of course represents the moles of barium hydroxide. So let’s get out the calculator

here, and let’s do that. So let’s get some room over here. So we take 0.0154 and we multiply that by 0.0274, and that gives us, this will be 4.22 times 10 to

the negative fourth, right? So that’s equal to 0.000422 moles of barium hydroxide. All right, next, let’s write

the neutralization reaction. So we have barium

hydroxide reacts with HCl. So barium hydroxide plus HCl

gives us, for our products, we have H plus and OH

minus, so that’s H20. And then our other product,

this is barium two plus, right? This is BA2 plus, and over

here we have Cl minus 1. So we have BA2 plus and CL minus 1, so you could cross those over. So BACl2, right? So BACl2, barium chloride,

as our other product here. All right, next we need to

balance our equation, right? We need to balance the

neutralization reaction here. So let’s start by

looking at the chlorines. So over here on the left,

we have one chlorine. On the right, we have two. So we need to put a two right here, and now we have two

chlorines on both sides. Next, let’s look at hydrogens. So on the left side, we

have two hydrogens here, and then we have two over here. So we have four hydrogens on the left. On the right, we have only two hydrogens. So we need to put a two

here for this coefficient to give us four hydrogens on the right. So now we have four, and we

should be balanced, right? Everything else should be balanced. Let’s look at the mole ratio

for barium hydroxide to HCl. For every, right, there’s a one here. So for every one mole of barium hydroxide, we have two moles of HCl. So we already calculated how

many moles of barium hydroxide that we used in our titration, right? That’s 0.000422. So therefore, we had twice as many of HCl. So we can multiply this number by two, and we’d figure out how

many moles of HCL we have. Or you could set up a proportion. Right, so if we’re

talking about a ratio of barium hydroxide to HCl, our mole ratio is one to two. Right, and our moles of barium hydroxide, let me go ahead and use

a different color here. That’s up here, that’s 0.000422

moles of barium hydroxide. Our goal is to find how many

moles of HCl were present. And so obviously you just need

to multiply 0.000422 by two. And so we get X is equal to 0.000844, right? That’s how many moles of HCl we have at our equivalence points. All right, so finally,

we just have to calculate the concentration of our

acid solution, right? Let’s go back up here so we

can see what we started with. Right, so we started with

20 milliliters of HCl. Right, and 20 milliliters would be, move our decimal place, 0.0200 liters. So now we have moles, right? We have moles, and we have liters. So we can calculate the concentration. All right, so the concentration of HCl in our original solution would be, we had 0.000844 moles. All right, divide that by liters. That was 0.0200 liters, right? 20 milliliters is equal to 0.0200 liters. And so we can do our calculation here. So we can take 0.000844, and we can divide that by 0.0200, and we get for our answer here 0.0422 molar. All right, so the concentration

of HCl is equal to 0.0422 molar, and we are finally done, right? That’s our concentration

of our acid solution. Let’s see what happens if you try to use MV is equal to MV, that shortcut that we learned about in the last video. So this would be MV is

equal to MV, and let’s do the molarity of the base

times the volume of the base is equal to the molarity of the acid times the volume of the acid. So for our base, the

concentration was 0.0154 molar, and the volume of base that we used was 27.4 milliliters in our titration. For the acid, we don’t

know what the molarity is. That’s what we’re trying

to find in the problem, and the volume was 20.0

milliliters, right? So let’s do that calculation. So trying to use the shortcut way, 0.0154 times 27.4 gives us that number, divide by 20, right? So we get 0.0211, right? So for our answer, for X, we get 0.0211 molar. And so you can see that’s not

the correct answer, right? Here we’ve got a

concentration that’s half of the concentration that we got

when we did it the longer way. And so if you want to use the

shortcut way for this problem, you would have to multiply by two, right? So if you multiply your answer by two, then you get the correct answer, 0.0422 molar. And a lot of the time,

students have a hard time figuring out what you do, right? So where do you mulitply by two? How do you do that? Of course, you can figure

it out by looking at your balanced equation up here, right? But it’s tricky for a lot of students. And so that’s why the shortcut way isn’t always the best way. You can still use it if you

understand how to use it, right? But it’s a little bit

better for these problems, when your mole ratio is not one to one, to go through the longer way and do it, if you want to be absolutely sure that you’re getting it correct.

Gotta love khan academy helping so many kids all over the world

and us big kids.

Yay I finally understand titration 😀

just in time for chem final today at 7 😀

hey !!!!

he didnt converted the mv volume into litrs!!!!!

thats goin wrong!!!

(Number of H+)MV=(Number of OH)MV

wouldn't it be easier to understand?

Thank you 🙂

his voice reminds me of cecil palmer from welcome to nightvale hahaa

Thanks! I can finally understand titration

SUPER LIKE . THANK YOU

WHAT ABOUt the SIGNIFICANT number

Do we really need to balance the neutralization reaction?

my chem final is about to fuck me tomorrow with no lube

What if you are given V1 and VH20 as a base

what if they tell you to calculate M1 and they give you an mL and 0.13M, but that is all.

They only give you NaOH and nothing else.

They give you the volume and on NaOH and nothing else.

My teacher taught us dm instead of L, is there a difference

Well, on the first problem it's moles over liters, not milliliters.

thank god for this video!! Finally I understand it

isn't this just stoichiometry

"What volume of 1.00-molar ammonium chloride must be added to 1.00-liter of 0.100-molar LiOH in order to achieve a pH of 9.4? "

Please help me with this

Aren't you supposed to divide by the total volume? Or is that just when you are solving for the pH of a titration..

You just made my eve.

Love Science <3

Thank you so much for this! I would have done so badly on my chem test otherwise

Do you have any extra exercises?

I didn't know this was easy, Thank you so much 😁

i love your videos……seriously!!!!

i love how you describe everything but tbh i hate your teaching style. you make it so hard to recognize what you have to do.

Why don't you write the net ionic equation?

What if u use

Acid. Base

MVn=MVn

n: stochiometry number of acid and base

who the fuck is this?? Wheres the other guy i like him more

Thank you for saving me for my test tomorrow, I was staring at my notes and I was so confused!!

Fucking analytical chemistry being a pain in the ass and the subject the keeps my GWA from getting high

can hardly c a thing

I am truly grateful for Khan Academy! 🙂 You can do anything guys!

Trash

Yeah, I have an a level chemistry exam tomorrow. Defo failing

awesome vedio but could be easy if you use simple values

When you learn nothing from college and everything from khan >

Best ever video on titration!

Excellent video! Really helped me for my exam!

You have no idea how long I've been struggling with this. Then in less than 10 mins you help me understand make me happy to be doing chemistry again. Thank you.

Thank you Khan Academy !

If you use the "shortcut" don't you just add in moles to the equation on each side?

why in earth will someone dislike this??

life hack: put Khan Academy on 1.5 speed and they talk like normal humans

very annoying the way the way you put the calculator over what you have written

Thx got a test tomorrow!!!

good I got 0.0422M as well

when you round up the volume for both using the shortcut way and multiply that by 2 you actually and then divide that by the conc of de base you actually still get the same answer too

its not that we multiply by two in every question the real shortcut is= normality *v1=normality *v2 and normality=molarity * n factor

i don't get this at all. i hate science so much like actually man i dont understand shit at all and im fucking stressing out fuck

very helpful!! Thank you.

If you are doing this for chem class make sure that you check with your teacher if the short cut is ok. I learned the hard way 🙂

Why couldn't you be my teacher…

Who's thinking?

Great video, understood it all with my very tired brain, the night before my exam

YAY! so helpful!

Hey…in the 'shourtcut method' using mole ratios does the trick…

To say;

Ma×Va = Na

—————————

Mb×Vb=Nb

Where; Ma is molarity of acid

Mb molarity of base

Vb volume of base

Va volume of acid

——— means divide lol

Na number of acid (from ratio)

Nb number of base (from ratio)

Thanks for the video great

Hope i helped with my formula

im failing in chemistry

Can't we just use MV1 = MV2 ?! The result then is 0.0210 , where's the problem ?!

Just become my teacher.

Thank you!!!

Thanks man!!

It took me half an hour to find a video for what I needed. Thank you so much!

Thank you Khan Academy for helping me learn things the public education system didn't give an f to teach me

I watched these videos for all of my Chem 2 class because my teacher taught me very little and I had to teach myself. So glad he gave me a pity C.

For the shortcut do u always milt by 2

Thank you! This is amazing👌🏻

ap chem exam tomorrow and this really saves my life

Here is the general equation for this kind of problem:

C*V/B = c*v/AThe variables C, c, V and v are the concentrations and volumes for for HCl and Ba(OH)₂, and B and A are their number of moles.

Thank you so much

saving my life thanks

Wow! I never quite got how my chemistry teacher did this. But you're so clear! I'm definitely gonna watch more of you instead of doing my homework…