3. Acids and Bases
Acids and Bases
One of the most challenging aspects of this chapter will be understanding and differentiating between different definitions that all sound kind of similar. We’re gonna move slowly through this, step-by-step.
The Lewis Definition
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The Lewis definition of acids and bases.
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So the next few videos are gonna be dedicated completely to acid base chemistry. And what I'm gonna do is I'm going to guide you through the easiest stuff first, which is just the definitions. Remember that, Injun Kim? There were a lot of different definitions of acids and bases. So we have toe, remember what those were Then I'm gonna take you through the more complex stuff, like basically chemical equilibrium. PKs. And eventually what you're gonna learn to do is predict the direction of a reaction in acid base equilibrium. And that's kind of cool. That's also going to be kind of. The ultimate goal of this section is to teach you how to predict that equilibrium. So let's get started with the easy stuff, Okay? First of all, before we get started, you need to know your strong six. So this is something from Gen. Kim that I usually tell you. You don't need to know. Everything from Gen. Came to be good or go, but this is one thing that you're never really allowed to forget. If I tell you that you're reacting with HCL and you don't know that that's a strong acid like come on, like you're slacking, riel hard. Alright. You should remember you're strong acids. Okay. Other than that, everything else I'm gonna teach you here today. Okay. So what I want to do is I want to start off with the most general definitions of acids and bases and then go to more specific ones, okay? And it turns out that the most general definition is going to be the Louis definition. Okay, now, I do wanna make one adjustment here. Notice that in your pdf, it looks fine. But in my pdf, it got messed up, so I'm just gonna write base base. We're comparing acids and bases. Right? Cool. So hopefully it didn't confuse you too much. All right, So the general definition, the most general definition of acids and bases is just gonna be the same as what we already learned in nuclear files on Electra files. Okay, so basically, what that means is remember that I said nuclear files have extra electrons. It's a negative. And then Electra files are missing electrons, so it's the same exact thing. What we're going to say is that in acid is gonna be an electron pair, except, er okay, so if one of these were to be an electron pair, except, er, which one would it be? Would it be the nuclear file or the electric file? Well, think about it. The name Electra file means electron lover. So this one would be the electric file. Does that make sense? So anytime I say electric file, that also means that I'm talking about a Lewis acid. Okay, Same exact thing. It's just a different way to say it. Then a Lewis base is gonna be an electron pair donor. Which of these is the donor of electrons? The nuclear file? Because the nuclear file has extra electrons. So anytime I say nuclear file, now, you know that I'm talking about a Lewis base, okay? And now that we linked these two things together now, you could even predict what the reaction is gonna look like. Based on what I taught you guys about nuclear files on electric files reacting together. Okay,
The Lewis definition is the most general of the definitions that applies to all cases. It's actually just another name for what we learned earlier as Nucleophiles and Electrophiles.
A Lewis Acid is an electron pair ACCEPTOR
A Lewis Base is an electron pair DONOR
Brønsted-Lowry Definition
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The Bronsted-Lowry definition of acids and bases.
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Now what I want to talk about is the more specific one, which is Bronston Larry, which on Lee has to do with protons. Okay, so the Bronston Larry definition on Lee has to do it with protons. And what it says is that maybe this is the one you remember Mawr from Gen Camp. What it says is that, uh, Bronson Laurie acid is gonna be a proton donor. You're gonna give away protons, and then a Bronston Laurie base is a proton except her. Okay, now, many of the time, most of the time, most of the time, these were gonna be the same most of the time. You're Lewis Acid is also going to be a bond, said Laurie Acid. Okay, so I would say more than 90% of time. They're the same, but sometimes they're different. And what that means is, sometimes one of these things is gonna be true. That it maybe it's an electron pair, except, er but the other one is not gonna be true. That which is that it's a proton donor. Okay, so that's what we have to learn today.
The Brønsted-Lowry definition is a more specific definition that only applies to some acids and bases. In this definition, electrons don’t matter- we only look at protons.
- A Brønsted-Lowry Acid is a proton DONOR
- A Brønsted-Lowry Base is a proton ACCEPTOR
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Lewis vs. Bronsted-Lowry Definition
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the easiest way to learn that is just to look at some examples. So what I want to do first is just go through these six examples and then I'm going to show you the difference between Bonds, the lorry and Lewis. Okay, so let's look at a first of all is water and water, I already told you is when it was an exception. What that means is that it can really do anything it wants, depending on what the other re agent is. So remember that it has electrons here has a lone pair there. Ah, lone pair there. And it also has protons. So what that means is that it can act as a lewis acid, meaning it could be an electron pair, except, er okay, because it could give away a proton make way for an electron pair. It can also be an electron pair donor, meaning that can give away one of its lone pairs. It can also be a bronze, said Laurie acid, meaning it could give away a proton. And it can also be a Bronson Laurie based mean that I can donate. I mean, that could accept a proton so it can do all of these things. So just think whenever you see water, all of the above, it could do whatever. Now, we're gonna go to a more specific re agent. That doesn't do all of these things. In fact, it's only gonna do one of them. Okay, this is boron. And if you guys remember from my talk on I told you as well octet rule how maney electrons does born want to have in a talk tech. It wants to have only six. Okay, six electrons. Okay. And what that means is that it actually prefers to have three bonds and six electrons. It's happy the way it is. But what that means is that it's always gonna have one empty orbital and that orbital is a P orbital. So boron always has an empty P orbital. The reason I'm teaching you this is because it seems kind of specific, but this comes up a lot in organic chemistry. One. So I want you guys to remember that Barnes kind of special. It always has that empty P orbital. There's actually another Adam that's very similar, and that's the one right under it in the periodic table. And that's aluminum. Aluminum also has an empty P orbital and then three bonds. Is that cool so far that empty orbital turns out, Since it's empty, it can accept electrons. Really, really well, okay, but it's not a good Proton donor. The reason is because if it gave away a proton, it would break its octet and then it would only have four electrons. Okay, So what that means is that Is this going to be an electron pair? Except er yes, If I say electron pair except, er which of these four is that? Look at my definitions. Above which one is the electron pair? Except er Lewis Acid. So it turns out that B H three is a really good Lewis acid. Okay, but now let's see. Is it also a bronze? Said Larry Acid, Which means is it a good Proton donor? No, it sucks. It actually is terrible. So it is not a bronze salary, I said, but it is a lewis acid. Isn't that interesting? So this is an example where the two different definitions don't line up exactly. Okay, Now let's talk about the bass part really quick. Is it a good Lewis base? Meaning doesn't give away electrons. Obviously not. It doesn't have any electrons, so no. And then is it good at accepting protons? Also know. Okay, So what that means is that it's on Lee one of these things, which is that it's a Lewis acid. Okay, now, I want you to hold on to that. But just keep in mind that this is different from water. How water was a good lewis acid. And brown said Lowry, which is like I said, about 90% of the molecules we encounter have both of them agreeing with each other. But then there are some special molecules like these guys that only do one of them. All right, so let's look at these other ones. Um, this is a molecule C is a molecule that I've introduced you guys before. It's called Paradyne, okay? And it has a lone pair here. Okay, So is it gonna be a good electron pair? Except, er no. If it accepted another lone pair that would break its octet, right? So, no, it's not a good electron pair. Except, er is it a good electron pair donor? Yeah, because it has a free lone pair just hanging out here. So it is a good election paired donor, or it's a good nuclear file. Or what would you say? Lewis base. Okay. Is it a good Bronstein acid? Meaning that it can donate protons? Yeah. Okay. Is it a good bronze? Did base mean that it can accept protons pretty well. Actually, it can. So this would be both one of those examples where it's both Ah, Lewis and a bronze did base. Okay, so I just want you guys to keep that in mind. These agree with each other because it can donate electrons, but it could also accept a proton. Okay, Now, let's look at this next one. So I'm gonna go through these a little quicker, but basically, now, I have, um, basically lone pairs on this. Oh, and what I want to know is that could that oxygen there be a lewis acid? Could it be an electron pair? Except er, actually, it could if it gave away this proton. If it gives away the proton, then it could accept two electrons. So it actually is a lewis acid. Is it a good Lewis base? Meaning that it's good at giving way? Electrons not really? Okay. Is it a good Bronstein acid? Meaning that it's good giveaway protons? Actually, yeah. We just said that it could give away this proton. So it's a bronze. Did. Acid is a good Bronston base, meaning that it can accept protons. No, not really. Okay, now, you might be wondering, Johnny, how did you know that this was gonna be a good acid and give away that proton? Well, think about the functional group. This is called carb oxalic acid. Okay, if you forgot that, remember that. Basically C o h is carb oxalic acid. So what that means is that it has a very acidic H. So it's easy to give that h away. And if it's giving the H way, then what is it doing? It's gonna except a lone pair. Okay, Now, let's talk about this next one. A double bond is a double bond. A good electron pair, except er So let's say I have electron pair, and now it's going to try to go into that dope one. No, that would be terrible. That would break the architects of two carbons. Okay. Is it a good electron pair donor? Okay. And actually, yes, it is because remember that I said that these electrons can donate to something else. I can move those electrons to some kind of electric file. So there's actually a really good Lewis base. Okay. Is it a bronze? Did acid meaning that it can donate? Protons don't. Not at all. It's not an acid. It all. Is it a good Bronstein base? Meaning that it's easy for to to, um, toe accept protons. And actually, no, it's not. This is not a good example of a bronze said base, because once again, I would be basically breaking in on Tet toe, accept a proton. Okay, so this is gonna be one of those examples where this is going to be mostly a Louis space, and it's not gonna be Ah, Bronze said based very much. Okay, it's gonna act more like a Louis. Basically, it's gonna be really good at giving away the electrons, Okay? But it's not very good in its normal state. It's not good at accepting its at accepting protons. Okay, so then we finally have this last one, which is just, um, Al Cane. Okay. And al cane. This one is un reactive. It doesn't have anything to react. Remember that we talked about re activities before and we talked about how you need a double bond. You need a die poll. You need a charge. Some strange, none of that. So this is just not gonna be anything. It's not gonna be good at donating protons, and it's also not going to be good at accepting them. Just it's not gonna do anything because it's un reactive. Okay, so in all these cases, I was looking for a reactive site. All of these had a reactive site, except this last one.
Let’s watch a few examples so you can get the hang of the differences between these definitions:
Heads up:By definition, any Brønsted-Lowry acid is also a Lewis acid. This is because if you are able to donate a proton, you are always able to accept an electron in return!
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Visualizing difference between definitions
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but I want you guys to visualize. Is this little circle chart up here? And I want to show you guys the difference between brought basically Bronson and a Bronson, Laurie and Lewis inside of this. So basically, um, water would be an example of ah Bronson Laurie acid. It could be a Bronx Laurie acid. Okay. Meaning that it's good at giving away protons. Okay. And that means that it's also considered a lewis acid. Because notice that Lewis is the more general definition. So every single type of acid can also be considered Lewis. Okay, whereas bh three, which is my second example, would be one that is on Leah Louis definition. It is not gonna be Brown said Larry. Okay. And the reason, I mean, obviously the reason is because it's outside of the bronze, said Laurie Circle. But another reason is because I explained to you, Is this a good proton donor? Is bh three good proton donor? No, because it would break its octet if it donated a proton. Does that kind of makes sense? So they're gonna be some Lewis acids in some Louis bases like bh three that are not gonna also be that are not going to be Bronx, said Larry. And that's important for us to know in terms of concepts your professor could ask you. That he could say, are all Lewis acids, Brown said. Larry Acids. And the answer is no, that would be false. You just look at this chart. You'd say BH three is not Brown, said Laurie. But now, if he reversed it and he said All. Brown said, Lowry acids are also Lewis acids. That's actually true because Bronson Larry Acids are in the smaller circle. So that's the one that's more specific. It still fits in the general, all right, so I just want you guys to know that.
General Features of Equilibrium
When determining how acids and bases react together, it important to understand the concepts of conjugates and Ke.
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Equilibrium constant and conjugates.
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Now, what I finally want to do is end off talking about equilibrium. And this is just a simple pattern that we're gonna use throughout all of these reactions. And all it says is this Ah, base will always attack an acid. So notice I'm already telling you what's gonna happen. A base negative will attack an acid. Positive to produce. Conjure gets scary word. Remember that from gen com congregates in the falling chemical path. So this is the way it works. Basically, you're always going to get your stronger base and you're stronger acids. Okay. Reacting together to make a weaker base and a weaker acid. Okay, so you always go from stronger toe weaker. It just makes sense. You're never gonna go from weaker or stronger. That that doesn't make any sense. Okay? And then what we're gonna do is everything that's on the right side of the arrow. Okay? Everything that's after reaction. We're gonna call that a conjugate. Okay? The conjugate means that's what happened after it reacted. Okay, So, basically what, and then everything beforehand, we're just gonna call it the regular base in the regular acid. Okay, So what that means is that my base is always gonna turn into a conjugate acid, and my acid is always going to turn into a conjugal base. I know that's a little bit confusing, and a lot of people mix that up, Okay? But that's just something you have to remember. Your base is going to turn into the a weaker acid, and then your acid is gonna turn into a weaker base than the ones that were on the other side. Okay, on Ben. Also, just that the K E has to do with the equilibrium constant. And all that saying is that it's always going to go to the right. Basically, k e over one means that it's going to the right if your congregants are weaker. Okay, if your contracts are weaker than it's going to the right, if you're confident you're stronger than it would go to the left because then it's going to go the other way. Okay, Does that kind of makes sense Now? I know that last part was a little bit rushed, but think we're gonna do tons of practice with this, So by the end of today, you're not gonna have a problem with congregates. Okay, so if you have any questions, let me know. But if not, let's move on to the next topic.
Drawing Reactions Based on Definitions
Even though we still have no idea what we are doing, we should be able to use patterns of nucleophiles and electrophiles, coupled with what we learned about how to draw arrows for mechanisms, to predict our first acid-base reactions.
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ProblemWhich of the following compound(s) cannot be characterized as a Lewis acid?
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ProblemWhich of the following compounds is most likely to have come from the stronger acid?
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Additional resources for Acids and Bases
PRACTICE PROBLEMS AND ACTIVITIES (48)
- Predict the products of the following acid–base reactions. (h) +NH3CH2COOH + 2 -OH ⇌
- Predict the products of the following acid–base reactions. (g) HCOOH + CH3O- ⇌
- Predict the products of the following acid–base reactions. (f) (CH3)3NH+ + -OH ⇌
- Predict the products of the following acid–base reactions. (e) H2O + NH3 ⇌
- Calculate the pH of the following solutions. a. 5.00 g of HBr in 100 mL of aqueous solution b. 1.50 g of NaOH ...
- Consider the following reaction: HBr+-C≡N⇌Br−+HC≡N g. What is the conjugate base of the acid on the right? ...
- Consider the following reaction: HBr+-C≡N⇌Br−+HC≡N c. What is the conjugate base of the acid on the left? d...
- Draw the conjugate acid of each of the following: a. CH3CH2OH b. CH3CH2O− c.
- a. What is the conjugate acid of each of the following? 1. NH3 2. Cl− 3. HO− 4. H2O
- In the following acid–base reactions, 1. draw Lewis structures of the reactants and the products. 2. determine...
- Predict the products of the following acid–base reactions. c. + -OH ⇌ d. HOCOOH + 2 -OH ⇌
- Predict the products of the following acid–base reactions. a. H2SO4 + CH3COO- ⇌ b. CH3COOH + (CH3)3N- ⇌
- Label the reactants in these acid–base reactions as Lewis acids (electrophiles) or Lewis bases (nucleophiles)....
- In the following acid–base reactions, 1. draw Lewis structures of the reactants and the products. 2. determine...
- The following compounds can all react as acids. CH3COOH CF3COOOH CF3CH2COOH < CH3CH2OH a. For each co...
- Ammonia appears in [TABLE 2-2 ] as both an acid and a conjugate base. a. Explain how ammonia can act as both a...
- What products are formed when each of the following reacts with HO− ? a. CH3OH b. +NH4
- Draw the products of the following reactions. Use curved arrows to show where the pair of electrons starts and...
- What products are formed when each of the following reacts with HO− ? e. +CH3 f. FeBr3
- Without using a calculator, estimate the pH of each of the following solutions: [HO−]=3.2×10−5 [H3O+]=8.3×...
- Consider the following reaction: HBr+-C≡N⇌Br−+HC≡N a. What is the acid on the left side of the equation? b....
- Which of the following are not acids? CH3COOH CO2 HNO2 HCOOH CCl4
- Write the equation that shows how a buffer made by dissolving CH3COOH and CH3COO−Na+ in water prevents the pH ...
- Antacids are compounds that neutralize stomach acid. Write the equations that show how Milk of Magnesia, Alka-...
- Draw the products of the following reactions: a. b. c.
- b. What is the conjugate base of each of the following? 1. NH3 2. HBr 3. HNO3 4. H2O
- Based on the one species that is identified for you, label the remaining molecules as acid, base, conjugate ac...
- Based on the one species that is identified for you, label the remaining molecules as acid, base, conjugate ac...
- Based on the one species that is identified for you, label the remaining molecules as acid, base, conjugate ac...
- Identify the acid from which the following conjugate bases were formed. [The most basic atom is indicated.] (...
- (•••) Predict the product of the following Lewis acid–Lewis base reactions. (d)
- What is the conjugate acid of each of the following bases? [The most basic atom is indicated.] (a)
- What is the conjugate base of each of the following acids? [The most acidic proton is indicated.] (d)
- What is the conjugate base of each of the following acids? [The most acidic proton is indicated.] (a)
- (•••) For each of the following molecules, predict the product that would form upon reaction of a single equiv...
- (•••) For each of the following molecules, predict the product that would form upon reaction of a single equiv...
- (•••) For each of the following molecules, predict the product that would form upon reaction of a single equiv...
- Provide an arrow-pushing mechanism for the following acid–base reactions. (d)
- (•••) For each of the following molecules, predict the product that would form upon reaction of a single equiv...
- (•••) For each of the following molecules, predict the product that would form upon reaction of a single equiv...
- In the following reactions, (iv) provide an arrow-pushing mechanism of the proton transfer that will occur, an...
- In the following reactions, (i) identify the acid and base, (ii) identify the most electron-rich atom in the b...
- In the following reactions, (iv) provide an arrow-pushing mechanism of the proton transfer that will occur, an...
- In the following reactions, (i) identify the acid and base, (ii) identify the most electron-rich atom in the b...
- In the following reactions, (iv) provide an arrow-pushing mechanism of the proton transfer that will occur, an...
- Provide an arrow-pushing mechanism for the following hypothetical acid half-reactions. [These are only intende...
- (••••) In addition to radicals, anions, and cations, a fourth class of reactive intermediates is carbenes. A n...
- What is the major product of the following reactions? f.