 Okay guys, if you don't mind, I think we finished with writing the molecular total and net ionic equations. If somebody can tell me differently then I'd be happy to change the slide. Some things I wanted to, some announcements I wanted to make before class today was remember that exam 3 is next Friday. I believe that's November 11th because I think today's the 12th, right? So I think it's November 11th that's Friday, but either whatever day that is, next Friday is when the exam is, okay? The night. Yeah, that's what I thought. So it's the 19th, right? 12th plus 7th. So I said the 11th? Whatever, you know? I'm already on the weekend. Or maybe I'm in Thursday still, I don't know, you know? Okay. The review session for exam 3, do you guys want one or will people come to it though? I mean I don't want to be the only one there like most of the review sessions. I know not the only one, one of four people there, okay? So I don't want to be that again. So if you guys will come to it, why don't we kind of make a time right now while we're thinking about it and it's recorded? So does anybody have any time, somebody will come to it, tell me what time, maybe on Monday would be a good day? Wednesday you want it, but what about, so unfortunately that means that the people that are online that have to take it on Wednesday don't get a chance to go to a review session. Okay, so well, on Tuesday, on Tuesday I have lab at one. So it's got to be, it's got to be after, after lab. Or so on Wednesday we could, or Tuesday, sorry, Monday we can do a review session instead of office hours. And that'll be after class, okay? Will that work for half of the people? So how many people will that work for, 11 to noon, or 10 to 11 on Monday? Okay, how many people, how about, how many people want that work for and still want to come to a review session? Okay, so what would be a better time for those of you who that doesn't work for? Again Wednesday doesn't work, you know, because of the online students. Tuesday after lab, does that work? Tuesday after lab? Okay. So I have lab from one to four, I think. So we could do four to five, or on Tuesday we could do another, because I have class until 9.15, so we could do like a 9.30 to 10.30. Four to five would be better? Four to five? No? Yeah. Well, I mean, 6.15 is getting about to my bedtime, because I get up at 4.30. So, yeah. Because I gotta work, you know, I gotta come in here and be, like, good for you guys, right? They all dressed up, huh? They've been up for two weeks, the practice test, yeah. And the solutions have been up since three days ago, right? I think two days ago or something. Three days ago, yeah. Okay, or Monday, okay? Too many days ago to even count, keep track of. Okay, so we'll have review sessions. Let's write these down. So instead of office hours, so we're canceling office hours on Monday, we're gonna have a review session for exam three. This is gonna be Monday, 10 to 11 a.m. And that's gonna be in this room, HSC 201. Okay, and the other one we said Tuesday, and we would rather, most of us, almost all of us except for one of us, I think, unfortunately, would rather have this four to five. Is that what we're thinking? Four to five? 11 to 12? No, unfortunately. Why don't you just come to this one, okay? You want to come to both? I'll record them, okay? So, yeah, but the thing is, is, like, I won't record it if, like, three people show up. That's one thing I won't do, because I'm sick of it, you know? I'm sick of, like, having just three people to talk to and everybody being like, oh, I'll just wait for this other thing. Tuesday. Yeah, Tuesday. Tuesday will be in here, too. So, if you can't show up, if you can't show up, then you can watch them. If, so, I mean, I've recorded some other sessions, too. I just haven't put them up, because there was a typo, but I'm hoping Inez will have her SIs next week prior to the exam. I know she's not going to be there today, so I'm sure she will be. I'm sure she will be. She hasn't informed me of anything differently. Okay, so that's the review sessions. Online people, you've got to reschedule your exam, okay, with the testing center before you can take it there, okay? The testing center has the new dates there, the 17th to the 19th, so make sure you schedule it maybe today or something like that, okay? The exam will cover from the end of Chapter 6 to whatever we finish on Monday lecture. I'm expecting that we'll get through Chapter 9, okay? And hopefully I'll be able to return Quiz 4 to you guys Monday. Of course, today's been a week since you've taken it, so. Okay, so like I said, those of you who didn't get papers that were in my lab, please come up to me after class and I'll give you those, okay? Okay, so if we could get started. So remember, the net ionic equation for this reaction here is proton aqueous plus hydroxide aqueous goes to water and this shouldn't say aqueous. I don't know. In all of these, it says aqueous. It should say liquid, L, okay? Water dissolved in water. This doesn't make very much sense, right? Okay, so yeah, everywhere it's got water and it says aqueous should say L. And notice, remember the last step is to simplify the net ionic equation from the coefficients 333 to 111, okay? Because it's a 1 to 1 to 1 ratio. Because the 3 to 3 to 3 ratio is a 1 to 1 to 1 ratio, right? Yeah. Yeah, good job. Okay, so remember we said that bases are things that when dissolved into water they have OH ions, right? They make OH ions. Well, most of the time the OH will be a part of the base like NaOH, right? So this is a common base sodium hydroxide or potassium hydroxide or magnesium hydroxide, okay, so on and so forth. Okay, most of those contain an OH within their ionic structure, within their formula unit. Unfortunately for you guys, because you're going to have to remember something else, there are some unusual bases, okay? And these bases, they produce OH ions in solution but when you look at their structures they don't have any OHs in them, okay? These things are like oxides here. So potassium oxide when combined with water will form two potassium ions and two hydroxide ions and things like ammonia. I believe we tested the pH of ammonia and we learned that it was basic but we hadn't learned about pH yet. So if you remember that reaction, you'll remember that, yeah, ammonia is basic but it doesn't have an OH group in it, right? Well, what it does is it will, so ammonia has a lone pair of electrons on it, right? It's NH3 with a lone pair of electrons. Those lone pair of electrons will remove one of the protons from water, creating OH minus. Let's go through that reaction mechanism just so you guys can see it. Can I erase everybody's got this stuff right? Write it down. We cool? Okay, so let's go through the ammonia reaction. Remember, so I'm going to draw kind of the structural formula for ammonia. You guys should be able to draw this on your own by now. So that's the structural formula for ammonia, right? Let's draw the structural formula for water now, like that, right? So hopefully you're not confused by these two structures. You should be able to build them by now. Let's think, let's look what happens. How do we produce OH minus ions from this reaction? What will happen is these lone pair electrons here, they're kind of like, remember, go-go gadget, you know, the go-go gadget and they steal the hydrogen here from water. So they go over there and they take that water or take that hydrogen and those electrons go to that oxygen there, okay? When we do that, so we're going to make a bond, right, between this nitrogen and this hydrogen and we're going to break the bond between that hydrogen and that oxygen. Does everybody see that from what the arrows are saying? So if we're going to make a bond between this nitrogen and hydrogen, you can look up there, what thing should we be making over here? NH4 plus, right? NH4 plus. I'm just going to draw the structural formula, okay? NH4 plus, right? So does everybody see how to make that right through that stuff? And what else are you going to make here? OH minus. You could put a bond in between that O and H if you want to, okay? OH minus, remember, is the reason the pH increases or becomes basic, okay? We haven't talked about pH, but just so I can start talking about it, when your pH is 7, that's neutral, right? Above 7 is basic and below 7 is acidic, okay? So now I can talk about it. It goes to 14 and 0, okay? So whenever you've got these things in solution, OH minus ions or hydroxide ions, this raises the pH and thereby makes it basic, okay? So things like ammonia, even though they don't have OH as present in their actual structure, right? They can do this type of a reaction when you put them with water and they'll form OH ions anyways, okay? So potassium oxides will do the same thing, okay? So you've got to watch oxides and things that have lone-pair electrons that can remove from the proton from water. So that's Arrhenius bases and acids. Bronsted-Lowry bases and acids, or the Bronsted-Lowry definition of bases and acids, are really more general than the Arrhenius bases and acids that say, well, if you've got an OH on you, you're a base. If you've got an H on you, you're an acid. The Bronsted-Lowry kind of does the opposite thing and says, well, an acid is something that can donate a hydrogen. So that's the same thing as an Arrhenius acid, but the base is something different. Bronsted-Lowry base, instead of saying it's a species that have a hydroxide ion in it, it's a species that can accept a proton, okay? So if you look here, this thing is a base, ammonia, right? Not because it has an OH ion in its structure, right? But it's because it can remove this proton to make this structure. So this thing accepted a proton, right? Does everybody see that? So this is a base due to this definition. And also, you can see that we have an acid in this equation too because it says a species that can donate a proton is an acid, right? So do you see anything donating a proton in this reaction? What is it? The answer is donating a proton, right? So donating and giving it up are like the same thing, okay? So if I'm giving something up, I'm donating it, okay? So in other words, since this thing is giving up its proton, what do we call it? Okay, now everybody tell me. So everybody, right? If something gives up a proton, what is it called? An acid, okay? So notice we've got a base and an acid, right? So most acid-base reactions, you'll see this. You've got a base and an acid, okay? Or it wouldn't be an acid-base reaction, right? Okay, so I prefer honestly to think about bases and acids in the Bronsted-Lowry sort of definition because it really generalizes things. It just says if I can accept or donate a proton, okay? And that's all it's about. Remember, we don't have to worry. Does it have a hydroxide on it? Does it not, okay? And you can see a couple more examples here. This is HCl plus water going to H3O plus. Do you guys remember what we called that molecule H3O plus? It has a name. The hydronium ion. So something you're going to have to remember because I'll say hydronium ion. And if you don't know it's H3O plus, then you don't know the problem, okay? And here's the other problem that we just did on the board here. You can see they're going with structural formulas as well, okay? Remember, I said things with lone pair electrons, right, can act as bases, right? Why can they act as bases? Look up there and tell me why they can act as bases. Because they can go take the thing, right? Lone pair electrons can take the proton from something else. Does everybody see that? So if you got a lone pair electron, it's like your inspector gadget hand, right? It can go and grab something off of something else, okay? Then, if that's the case, then why didn't we say water is a base? Well, I mean, we could have done take this electrons and take this thing away, right? Why can't we do that? Okay, well, we'll get to that point later, I guess. I wanted to talk about something else first. But I want you to think about it, okay? I want you to think about it. We'll talk about it. So solutions of, so binary acids, what are binary acids? These are things that have two atoms, okay? Like HCl that have a proton that's donatable, okay? So some binary acids that you probably know are HCl. Can anybody think of another one? Two atoms and is an acid. Now what does an acid have to have, guys? A hydrogen, okay? So any Cl doesn't have a hydrogen, right? HBr, right? That's a good one. Can anybody think of another one? Yeah, Hf, right? Okay, so those are the binary acids. Things that have a proton and one other atom. How come they have to be all of those things? Because those are the only things that make one bond, right? So you should know that already. They only make one bond, okay? Okay, the interesting thing is, is that these, what we call acids, these binary acids, they're not acids unless they're, within aqueous solution, okay? So they're actually gases by themselves. They're really, actually very strong acids, but we don't use them as acids, like in the chemistry laboratory or something, unless they're dissolved into water, okay? That's like our one molar HCl or something like that, okay? So in other words, these things are, when they're free, they're actually very strong acids. These things are, when they're free, when they're not within a water solution, they're so small, right, that they have very small intermolecular forces, so they can't hold themselves together very well, so they'll be in the gaseous form, okay? But once you dissolve, so we call it, hydrogen chloride when it's in the gaseous form, okay? But we don't call it hydrogen chloride when it's an acid, okay? Yeah, we call it hydrochloric acid, okay? So that's what you want to remember, okay? So some hydrogen-containing compounds such as HCl, HI, HBr, H2S form aesthetic solutions when they're dissolved in water, and their names change, okay? So instead of calling it hydrogen chloride, we drop the word hydrogen, and we add hydro to it, okay? So it's called hydro now, hydrochloride now, right? But then we drop id and add ik, so now it's hydrochloric, and then at the end we just stick the word acid on it, okay? So HCl is now called hydrochloric acid, not hydrogen chloride, okay? Let's talk, let's go back to this equation and we can look at this equation up here. Notice when we look at these as the reactants, remember when we have this type of reaction arrow, it's kind of ambiguous what the reactants and what the products are because this reaction could go both ways, right? If I'm looking at this top arrow, we would refer to these as the reactants and these as the products, right? But if I was looking at this bottom arrow, we shouldn't refer to it that way. We would refer to these as the reactants and these as the products. If I'm looking at both arrows in conjunction with each other, like I said, it's kind of ambiguous as to what's the reactants and what's the products. I would assume that if a reaction was written in this fashion that the initial thing that was dumped into the reaction vessel was these things, okay? Because we, as Americans, right from left to right, okay? If maybe I was in Saudi Arabia or something like that, I would imagine opposite, you know? But still, even if I put these things in first, right? After some time, I would have this, this, this, and this in solution, okay? And at that point, it would be ambiguous as to what's the reactants and what's the products. So you've got to remember that these reactions are going both ways, okay? That being said, this is an acid-base reaction going in the forward direction, right? Everybody agrees with me by now, hopefully, right? Because we've got an acid in a base, one's accepting the proton, one's donating the proton, blah, blah, blah, right? Let's look at the opposite reaction. What type of a reaction is that? So do you guys see what's going on? So what I want you guys to think about is you've got to take one of these things and make one of these things out of it, right? So that's what we're doing. So what's happening to this OH as I go, yeah, as I go here? It's doing what? So I heard, yeah, it's grabbing a proton, right? Or it's accepting a proton. What do we call things that accept protons? A base, okay? So this is a what? Well, it's a conjugate base. I haven't told you anything about that yet, but yeah, it is a conjugate base. So this is a base. Yeah. You're going to confuse me, man. Okay. So what is it doing? What is it doing here, right? It's taking its lone pair electrons here, right? So the reaction mechanism. And what are these going to? Tell me. A hydrogen? Right, yeah. And it's jacking it, right? Like that, okay? So what's happening to this species here? It's losing a proton. Or in the parlance of Bronsted-Lowry, we say it's donating a proton, okay? Okay. So if something donates a proton, what do we call that? An acid, okay. So notice the acid-base reaction goes back and forth, okay? So it's both a reaction, an acid-base reaction going in the forward direction and an acid-base reaction going in the reverse direction. Does that make sense? Okay, cool. So because we are in America, right, in learning chemistry, we assume that this is the initial stuff. So we call this the proper acid and base, okay? But like Michael mentioned earlier, on the other side of the reaction, they're also called acid-base but they have a special name because they are derived from these things here. We call them the conjugate acid and the conjugate base, okay? So if I were to give you this molecule, ammonia, on a test and I asked you, what's the conjugate acid of that molecule? You should tell me, what? What's the percentage for plus? Okay? So what have I done here to get the conjugate acid? What did I add? A hydrogen and a plus charge or a proton, right? That's what I really added. It's not just a hydrogen. I added a hydrogen and a plus charge, right? Okay? That's all you gotta do. I'm gonna take away from this reaction and do kind of these sort of things for a second, okay? So if I asked you, what's the conjugate acid of this molecule here? Conjugate acid, that's what it is. OH-? What did we just say OH- is? Can that be an acid if it's a base? I mean, not yet, right? So how do I just say we make conjugate acids? Add a hydrogen and a plus charge, right? If we add that, does that make OH-? Thank you, H3O+. Okay? How do I get a conjugate base? How about that? Take away what? H and plus, okay? So don't just think we do it one way. We gotta do it the opposite way, too, right? If we add a hydrogen, we have to take away H+, okay? So, let's draw the conjugate base for this thing. What's the conjugate base? Cl-, right? Why is that? Because I just told you you have to not only take away the H, but you gotta take away a plus charge. If you subtract a plus charge, what do you get? A minus charge, right? So what's the conjugate base here? F-, right? And then the final one down there? F-, right? Okay, cool. Okay. So, hopefully you've noticed one thing you might not have yet, but if you connect all of this stuff together, you notice that again, something we were referring to before, water here is acting as an acid, right? Because it's getting its proton removed. But water here is acting as a what? As a base, right? Because it's removing a proton. Okay, so that's weird. Again, remember we talked about that earlier. Why doesn't it go the opposite way? Okay? Here's some conjugate acid and base pair problems that you can go over on your own. Okay. So let's talk about water and this nature of water, okay? So water, just like other substances that have both acid and basic properties to them, are known as amphiprotic molecules, okay? Amphiprotic. And that just means it's got the ability to act as a base or the ability to act as an acid. Of course, water's going to be the most commonly used solvent for both acids and bases as you probably well know by now from working in the laboratory. And you can see here in these two reaction equations water acting as a base here as a proton acceptor taking the proton away from HCl and water acting as an acid, which is happening over here. So notice this over here is the conjugate acid of water, this here is the conjugate base of water, okay? Okay, so let's talk about strong acids and strong bases and weak acids and weak bases. For those of you who watch the lecture on of Wednesday's class that I re-recorded, right? You'll know that we talked a little bit about that stuff when we were talking about percentage in solution, okay? So, that's kind of what we're doing here. Remember kind of my little graphs that we were showing? That's what's showing here, okay? So if you go back and look at that analysis you can understand what these graphs are saying here. Okay? Or you could just listen to me right now, I guess. So, of course, just as everything else has differences in strength, acids and bases also have differences in strength. So you could have, as you can imagine, a weak acid which is not very strong or a strong acid which is very strong, okay? Which will, you know, give up a lot of protons, okay? So, what we say is strong acids and strong bases completely dissociate in water, okay? So, instead of this equation where we have a back and forth arrow like what's presented here, we should just have a straight forward arrow, okay? So why don't you guys cross that little back and forth arrow out up there and put a straight forward arrow? So that means, what does that mean? When we have that type of an arrow as opposed to a back and forth arrow? It just goes to one way, right? So do these guys, the products, do they go back to the reactants? Uh-uh, okay? So they don't go back to the reactants, okay? So, when you have a reaction like this, that's a strong acid. So what we say completely dissociates, dissociation means breaking apart, okay? Breaking apart into the proton and the acids into a conjugate base. Kind of like what's happened here. This is a strong acid, HCl, it will completely dissociate into its proton and its conjugate base. Okay? Got it? Okay, good. Yeah. Notice here, is this a strong acid, water? No. How do you know that? Look at that arrow, right? That arrow told you. Okay? That arrow told you. So, can I ask you another question? Does water completely dissociate when you put it into water? No. No, it doesn't, right? They even know that's a silly question, right? What does that mean? Water is a strong acid, is that what that means? It's a weak acid, okay? That's why when you take a drink of water it doesn't burn your tongue off, right? Because it's not a strong acid. But it does have these properties to it. So notice here, when we have a strong acid in solution at time zero, all we have is reactants. HA. Okay? Does everybody see this here? Notice, no products are shown. Okay? After the reaction, at time, reaction is done, at time infinity, if you will. Okay? What do we have? Here's the three species that are in solution, HA, H3O plus and A minus, right? How much HA do we have? Zero, because it's all, what? It's all broken apart, right? Into its conjugate base and its proton. Okay? In this case it shows it H3O plus. What we have, we'll talk about that right now. Can I erase this reaction here? Everybody's got that. So, why does it say, instead of like how I wrote it here, why does it say H3O plus? Well, H plus plus H2O goes to H3O plus. Okay? Without this in solution, what you find is that protons are very, very tiny, okay? Even in relation to atoms, okay? They're exceedingly small, okay? But it has a full positive charge on it, just like if cesium lost its electron, right? With 55 protons in its nucleus, right? So, it's much bigger than one proton, right? So, cesium and a proton, right, would have the same magnitude of charge, right? That would have a plus one charge just like a proton would have a plus one charge, right? They lost an electron, okay? But what you find is that with the big atoms, they don't mind having a positive charge. What they do is they can break that positive charge up into little pieces of a positive charge or little delta positives, okay? And push that positive charge all around the circumference of their sphere, okay? Hydrogen could do that too, but its sphere is so tiny compared to these other atoms, okay? So, it's still got this major big charge on it, but it wants to break it up as much as possible. So, its surface is so tiny that it can't break it up very well. So, what happens is recall water is polar or non-polar, do you guys remember? Polar, right? So, what does that mean if something's polar? No, no, no, it does not attract. No. What does it mean that it is polar? It's got a partial positive, right? And a partial negative charge, right? So, that's partially negative, partially positive, right? What'll happen? So, when you have these protons free-floating in solution, well, solution, there's all these solvent molecules of water, right? This thing's like, crap, I can't stand having this big positive charge on me. This thing's like, well, I've got a bunch of negative charge, so I'll help you out with it. So, it kind of associates until it makes that bond. And now, we take the positive charge and move it to our oxygen there, and we have the hydronium ion now, right? Okay? So, whenever you see so, what I'm saying is whenever you see this and whenever you see this you can almost treat them as the same thing, okay? This thing is acid just as much as this thing is acid, okay? Read the book if you don't understand it, okay? Think I've gone through enough explanation. Okay. So, or go watch the lecture from last time. So, let's talk about weak acids. So, what happens in a weak acid that's different relative to a strong acid, right? You see at the beginning? Well, we've got that back and forth arrow, right? With a weak acid. But at the beginning, right? Time zero, we only have reactant. But at time infinity when the reactions quote-unquote over, or you know, at equilibrium actually, right? What do we have? We've got products, definitely. But the overwhelming majority of the stuff that's in solution is still the original reacting, okay? Why is that? Because weak acids dissociate very, very small amount. That's why, again, that when you drink some water it doesn't burn your tongue off, right? Because it's a weak acid. It only dissociates a little bit. Okay? So, this is like acetic acid in vinegar, or other acids that you can consume on, you know, a daily basis, you know, or sugar, or anything that's got a removable proton on it, okay? So, this is what they do. And that's the difference in relation to a strong acid, okay? Okay, so let's talk about the auto-ionization of water. So, like we said water is both a weak acid and a weak base, right? So, if you got an acid and a base together, right? They'll react with each other to form some products, right? They'll do acid-base reaction. So, if we've got one water molecule along with another molecule, one water molecule will have its lone perelectrons take the proton from the other one, okay? If we do that, we get H3O plus here and OH minus here, right? Everybody see that, right? Okay. So, this reaction is written out above. Notice it's a back and forth arrow. So, the reaction goes both forward and backwards, okay? In fact, it doesn't go forward to very much extent. 1.0 times 10 to the negative 14th molar. So, very, very tiny amount. But, have we started doing equilibrium constants yet? Have we do K? We have, right? Okay, so we can say the K of this reaction, right? It's going to be the products over the reactants, right? But remember, when reactants are solids or liquids, what do we do with them in the equilibrium constant? You don't put them, right? Okay, so, you could imagine this would be the original equilibrium constant. But we're just going to remove this term here, okay? So, what happens is when we take that water out, since that's a constant, we get a new expression that we call the KW, okay? That's the equilibrium constant of water. That's why it says W, okay? KW is going to be the concentration, remember when it has brackets around it that's molar concentration. So, the concentration of hydronium ions times the concentration of hydroxide ions. That's always going to be 1.0 times 10 to the negative 14th. Okay? Remember, the equilibrium constant doesn't have units, okay? This is, it says at 25 degrees celsius that's because if you change the temperature the equilibrium constant will change. But all of our problems on test or anything will be at 25 degrees celsius, okay? So, if you look at this, you should realize that you can algebraically manipulate this to mean that, well, this times this must equal that. They have to break apart, of course, because you only have one water molecule that's breaking into two. So, since you only got one to break into two, it has to be equal amounts, right? They have to be equal amounts of each other. So, since you got 1 times 10 to the negative 14th as the equilibrium constant each of these must be present in 1.0 times 10 to the negative 7th molar in solution. And then, yeah. So, I'd like you to look at the next couple of slides because we'll be doing pH, okay? And that'll be one of the last topics we cover. pH and buffers before the test, okay? So, I think the sign-in sheet's still out there. If you want to sign in, remember review session on Monday. Good luck studying, guys. Oh, thank you. I've got papers for you. And...