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Calculate the percent ionization of benzoic acid having the following concentrations: (a) $0.20 \mathrm{M},$ (b) $0.00020 M$.

57%

Chemistry 102

Chapter 15

Acids and Bases

Liquids

Carleton College

University of Maryland - University College

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.

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Calculate the percent ion…

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for this session. We're going to calculate the percent ionization of a weak acid. I'm gonna write an equation. A chemical reaction for a weak acid dissociating. We're gonna represent any acid by using h A. That's our quickest asset, and that'll dissociated into their age plus and are okay, so if we're going to write an equilibrium expression K expression, which is there as a dissociation constant that will equal the product of H plus times a divided by the concentration of the asset. And in this problem, what we're going to do is we're gonna consider a nice table. So our first step will be I'm gonna call it Ice Light and then we're going Teoh, find the concentrations of age less, which will be the concentrations, same concentration for a minus. And, um then we're going to figure out what percent has been I nights. Okay, let's begin. We're given the following information. We're starting with two situations are first is 0.20 Moeller benzo gas it and I think that's all we're given for the first part. But we can look up and find that the k A for Ben's OIC acid 6.5 times 10 to the minus five. That's the K Okay. And then for our little ice light table I see. Remember, we're after I equilibrium expressions. Our initial concentration is 0.20 Moller for H A And then he had HP loss and a minus. This will be zero. This will be zero now, some small amount of my benzoate gas. It is going to dissociate and we'll call that amount X and the concentration of the original Benzo kassid will diminish by acts. So I figured this out are equilibrium concentrations for Agent Air X. You know, for every he's have our asset, that's dissociates. We get one hydrogen and one Anna, and this will be 0.20 minus X. But these are the three numbers and carried to the next page. So the concentration of our asset is 0.20 minus axes. Rommel, Mullah Parretti's H plus A, our X and X. Now, since our K A is so small 6.5 times 10 to the minus fit, we can say that this is approximately pulled a 0.20 because this amount that's going Teoh soc is pretty small. Now we're gonna put it into R K A equation. So K a 6.5 times 10 to the minus fifth equals. And if this is X and this is X, multiply these two my my H concentration and my A concentration of the same. Since they're in the numerator, we get X squared and get 0.20 on the bottom. Do your calculator magic. And when you're done with this, you should find out that your concentration of the hydrogen ion on the and I and our 0.361 Moeller Okay, so this is like stage one. Now we again asked, what is the percent ionization and I were going to do for percent ionization? We're going to take the concentration of the products divided by my initial concentration times 100 So I mean is 0.361 divided by 0.20 times 100 and I believe this one could go to two significant figures that will give me 1.8%. And that's the final answer for this first part. Now, for the second part will be much easier. We're doing the same thing. But we have a concentration this time. R h a concentration this time is gonna be 0.0 000 That's our initial concentration. So when I look at, let's make this forage. I'm going to replace this number and this number with 0.20 Let's do it. So my okay is the same. This is an still X squared my denominator. 00 0300 I do my math on this. I'm sorry about that. I forgot to do my mouth for the second problem. It's gonna be the same just with decimals. But I want to make sure you got it. And that, um, take my square root of that. Now I get 1.14 times 10 domains for us is my concentration of X and A. So this one don't take 1.14 times 10 to the minus for divide that by 0.20 if I please. Times 100. I'm getting a bad answer here. I'm getting a bit well known. Maybe not. I'm getting a 57 percent. So in the lower concentrations, more of its going to disassociate. Okay. Thanks for listening.

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