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Compare the pH of a $0.040 M$ HCl solution with that of a $0.040 \mathrm{M} \mathrm{H}_{2} \mathrm{SO}_{4}$ solution. (Hint: $\mathrm{H}_{2} \mathrm{SO}_{4}$ is a strong acid; $K_{\mathrm{a}}$ for $\mathrm{HSO}_{4}^{-}=1.3 \times 10^{-2}$.)

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concentration of $\mathrm{H}+=0.02+0.04=0.06 \mathrm{mol} / \mathrm{dm}^{3}$ $\mathrm{pH}=-\lg (0.06)=1.22$

Chemistry 102

Chapter 15

Acids and Bases

Liquids

University of Maryland - University College

Brown University

University of Toronto

Lectures

03:07

A liquid is a nearly incompressible fluid that conforms to the shape of its container but retains a (nearly) constant volume independent of pressure. As such, a liquid is one of the four fundamental states of matter (the others being solid, gas and plasma). A liquid is made up of tiny vibrating particles of matter, such as atoms, held together by intermolecular bonds. Water is, by far, the most common liquid on Earth. Like a gas, a liquid is able to flow and take the shape of a container. Most liquids resist compression, although others can be compressed. Unlike a gas, a liquid does not disperse to fill every space of a container, and maintains a fairly constant density. A distinctive property of the liquid state is surface tension, leading to wetting phenomena.

04:38

A liquid is a state of matter in which a substance changes its shape easily and takes the form of its container, and in which the substance retains a constant volume independent of pressure. As a result of this, a liquid does not maintain a definite shape, and its volume is variable. The characteristic properties of a liquid are surface tension, viscosity, and capillarity. The liquid state has a definite volume, but it also has a definite surface. The volume is uniform throughout the whole of the liquid. Solids have a fixed shape and a definite volume, but they do not have a definite surface. The volume of a solid does not vary, but the volume of a liquid may vary.

01:50

Compare the $\mathrm{pH}$ …

06:10

01:51

The pH of a solution of 0.…

03:32

Calculate the $\mathrm{pH}…

03:16

What is the $\mathrm{pH}$ …

03:20

01:14

Okay, so we're given 0.4 Moeller moles per liter off hydrochloric acid and the same concentration of sulfuric acid. We have to find out the pH for each of these and compare them the so they're both the same concentration. They're both strong acids. So how are they going to be different? Well, we're gonna find out. First of all, let's look at hydrochloric acid. It's a strong acid, so it's going to give off pro turns and, ah, the conjugal base. It's gonna dissociated 100%. Since it's a strong acid. That means we know our protein concentration will be the entire 0.0 for most for leader. And so we can easily find the pH of this hydrochloric acid. We just do the negative log of 0.4 and what do we get? 1.4. So we have a pH of 1.4. All right, So what's the deal with so ferric acid? Well, let's look at it first of all, like ah, like hydrochloric acid and give off protons. It's gonna have a congregate base each eso four negative, but that hs a for negative. Well, I'll tell you in a minute. But this part is 100% just like the HCL. Which means we know that the proton concentration is 0.4 here. However, what I was about to tell you is the, um as you can probably see, they're still on ionized herbal age on the agents before, so it can act Not as strong of an acid, but a week. Your acid that can give off an additional concentration off protons leaving behind a a, uh, conjugal base that cannot be ionized anymore. But, um, to get the full pH than of the 0.4 h. U s. A four solution, we're going to figure out what this concentration of H would be. So let's call it X for now. So the concentration are total concentration for each to us of four is going to be 0.4 plus this X that we need to find out. So what are we going to need to do? Well, we better look at this ionization constant. And as you probably know, it's the proton concentration times, the and I and concentration. We're going Teoh, that's over. The just So for the original acid weak acid in the question they did give us this value. The K is 1.3 times sending the negative to for hs a four negative. Um, we're gonna call the Unknown Concentration Acts and both h plus and s. A four to negative constellations will be the same. So they're both X and, uh, their remaining that hs a four will be the 40.0 for minus that x and we can rewrite the x Times X as X squared. All right, so I'm just gonna fix that for, um, let's multiply to get 5.2 times in the negative four. We also got a do the 1.3 times in the neck of two times that negative acts. So we get that and left, and we're we just have X squared left on the right. So rearrange X squared on the left and then add the 1.3 times 10 to the negative two x and subtract the 5.2 times in the negative form and set it equal to zero. And we have what we need for the quadratic equation, and I'll write it all out in case you don't know that off the top of your head. So we're gonna have to do this and know what you're a is A is one B is the 1.3 to send in the negative two and C is the negative. 5.2 times 10 to the negative for so now plug him in. It looks scary, but it's just plugging in those numbers. Just make sure you take your time and get everything plugged in the right way. Now, I did forget. Don't forget, this is squared, and that's two times one, which is this too. But, um, so do up some of the math. You should get 1.69 times 10 to the negative for minus 2.8 times in the negative. Three all over too. Uh, now, finish all that square root stuff, and you should get 4.74 times to the negative too. Okay, so now we're ready to get to possible X values. The one is 0.172 You could also get negative 0.30 tube. Understand? A negative number makes no sense, which allows us to narrow it down to the positive number. So now we do have our X. So let's go back to this. Ah, formula we had made. I'm talking about the screen formula. The total we had 0.4 But we didn't know the X Well, now we do. So let's plug it in. 0.172 And what is that equal? 0.5 seven to? So now we have the total protein concentration for the sulfuric acid, and only one thing left to do is to find the pH. So take the negative log of that total concentration and you should get 1.24 So, um, we had 1.4 for the hydrochloric acid, and we have one point 2/4 for the sulfuric acid. So you can see even though they're both strong acids and they both started the same concentration, the sulfuric acid ends up with a slightly lower pH. And why is that? While the differences the, um, the number off ionized herbal h is so sulfuric acid has to. So you have to take into account as we did the second, um, I unicycle hydrogen for sulfuric acid. So that's a diaper product acid. So it gets not much more strength, but a little more so There you go.

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