WEBVTT 00:00:00.030 --> 00:00:02.410 The following content is provided under a Creative 00:00:02.410 --> 00:00:03.830 Commons license. 00:00:03.830 --> 00:00:06.840 Your support will help MIT OpenCourseWare continue to 00:00:06.840 --> 00:00:10.510 offer high-quality educational resources for free. 00:00:10.510 --> 00:00:13.390 To make a donation or view additional materials from 00:00:13.390 --> 00:00:17.190 hundreds of MIT courses, visit MIT OpenCourseWare at 00:00:17.190 --> 00:00:18.440 ocw.mit.edu. 00:00:21.520 --> 00:00:23.000 PROFESSOR: So a couple of announcements. 00:00:23.000 --> 00:00:24.870 Weekly quiz Tuesday. 00:00:24.870 --> 00:00:28.450 And also on Tuesday, I want to draw your attention to the 00:00:28.450 --> 00:00:31.050 event in the slide. 00:00:31.050 --> 00:00:34.340 We have a poster here for a lecture that will occur right 00:00:34.340 --> 00:00:39.470 in this room, at 4:00 on Tuesday. 00:00:39.470 --> 00:00:41.260 And it's entitled the Wolf Lecture. 00:00:41.260 --> 00:00:44.480 The Wolf Lecture was established here about 30 00:00:44.480 --> 00:00:47.550 years ago in honor of Professor John Wolf. 00:00:47.550 --> 00:00:50.370 John Wolf was an antecedent of mine. 00:00:50.370 --> 00:00:53.760 He was the person that invented 3091. 00:00:53.760 --> 00:00:59.550 And in 1961, he dared, as a metallurgist, to launch a 00:00:59.550 --> 00:01:01.420 variant of freshman chemistry. 00:01:01.420 --> 00:01:05.590 And you're the beneficiaries of John Wolf's initiative. 00:01:05.590 --> 00:01:11.370 And he also was a spectacular teacher, quite a showman. 00:01:11.370 --> 00:01:14.255 And in his honor, they instituted in the Department 00:01:14.255 --> 00:01:16.770 of Material Science and Engineering, the Wolf Lecture, 00:01:16.770 --> 00:01:21.360 which, as the poster says, is the entire community is 00:01:21.360 --> 00:01:24.670 invited to attend, but it's geared towards freshman. 00:01:24.670 --> 00:01:28.340 So this is a lecture that the rules are. 00:01:28.340 --> 00:01:31.490 Talk about whatever you want in terms of material science 00:01:31.490 --> 00:01:34.420 and engineering, but make it entertaining, and make it 00:01:34.420 --> 00:01:37.650 engaging and accessible to freshmen. 00:01:37.650 --> 00:01:39.790 You should go to lectures. 00:01:39.790 --> 00:01:41.550 If you can't go to this one, then by all 00:01:41.550 --> 00:01:42.820 means, go to other seminars. 00:01:42.820 --> 00:01:46.150 If all you do when you come to MIT is go to class, you're 00:01:46.150 --> 00:01:48.240 missing out on some of the richness here. 00:01:48.240 --> 00:01:51.800 We have all sorts of people coming through here every day. 00:01:51.800 --> 00:01:54.210 And you can go to these seminars, you can learn a lot. 00:01:54.210 --> 00:01:56.600 You might say, well, I'm just a freshman, I'm not going to 00:01:56.600 --> 00:01:57.660 understand everything. 00:01:57.660 --> 00:01:58.490 I go to these things. 00:01:58.490 --> 00:02:00.070 I don't understand everything. 00:02:00.070 --> 00:02:02.300 But I learn something, because the first few minutes of the 00:02:02.300 --> 00:02:05.320 lecture, if the speaker is any good, he or she is going to 00:02:05.320 --> 00:02:07.650 set up the topic for you. 00:02:07.650 --> 00:02:09.850 If you follow the first five minutes, you'll have something 00:02:09.850 --> 00:02:13.630 that, you know, gets you oriented to the topic. 00:02:13.630 --> 00:02:16.040 And then the other thing, the other reason to go-- you see 00:02:16.040 --> 00:02:17.380 this on the poster-- 00:02:17.380 --> 00:02:20.960 room 10-250, reception immediately following. 00:02:20.960 --> 00:02:23.650 That means there will be refreshments! 00:02:23.650 --> 00:02:25.020 Food, for that, you know, 00:02:25.020 --> 00:02:26.700 pick-me-up in the late afternoon. 00:02:26.700 --> 00:02:29.330 So you go to the seminar, you know, sometimes they have 00:02:29.330 --> 00:02:32.810 refreshments before the speaker. 00:02:32.810 --> 00:02:35.830 I'm not going to tell you have to go into the seminar, having 00:02:35.830 --> 00:02:39.870 eaten the food and partaken of the refreshments. 00:02:39.870 --> 00:02:40.970 You didn't hear me say that. 00:02:40.970 --> 00:02:43.420 But anyways, there's always food around here. 00:02:43.420 --> 00:02:44.440 Go to this one. 00:02:44.440 --> 00:02:45.350 I think you'll enjoy it. 00:02:45.350 --> 00:02:47.610 And the speaker is Professor Michael Rubner. 00:02:47.610 --> 00:02:51.320 He's a faculty member in course 3. 00:02:51.320 --> 00:02:53.350 An excellent teacher. 00:02:53.350 --> 00:02:56.190 As you see, MacVicar Faculty Fellow, which means he's been 00:02:56.190 --> 00:02:57.680 acknowledged as a good teacher. 00:02:57.680 --> 00:02:59.340 I think you'll learn a lot. 00:02:59.340 --> 00:03:01.780 And he's talking about nature-inspired, so 00:03:01.780 --> 00:03:05.270 biomimetics, how we see things in nature and then mimic that 00:03:05.270 --> 00:03:08.520 design in advanced material science. 00:03:08.520 --> 00:03:08.990 OK. 00:03:08.990 --> 00:03:09.930 Enough said. 00:03:09.930 --> 00:03:11.300 Let's get on with the lesson. 00:03:11.300 --> 00:03:14.420 Last day we started looking at solutions, and we recognized 00:03:14.420 --> 00:03:17.450 that bonding is the key to understanding, and it's 00:03:17.450 --> 00:03:21.130 encapsulated in that catch-all phrase, like dissolves like. 00:03:21.130 --> 00:03:24.240 And towards the end, we talked about Ksp as a metric that 00:03:24.240 --> 00:03:26.780 helps us understand common ion effect. 00:03:26.780 --> 00:03:30.780 Common ion effect, again, if I tell you you have, say, 100 00:03:30.780 --> 00:03:34.785 units of sodium chloride that can go into solution, you 00:03:34.785 --> 00:03:36.610 would say, that's the solubility limit. 00:03:36.610 --> 00:03:38.960 But then if I tell you, I've got a solution that already 00:03:38.960 --> 00:03:42.540 contains 25 units of sodium chloride, that's a no-brainer. 00:03:42.540 --> 00:03:44.820 You've only got another 75 units to go. 00:03:44.820 --> 00:03:47.470 Now I say I've got potassium chloride in there. 00:03:47.470 --> 00:03:49.330 So now you stop and think, wait a minute. 00:03:49.330 --> 00:03:52.190 It's not sodium chloride, but it is a chloride. 00:03:52.190 --> 00:03:53.760 How do I think about this? 00:03:53.760 --> 00:03:57.660 Common ion effect through Ksp helps you reason through it. 00:03:57.660 --> 00:04:00.440 It's when you have more than one solute, and one of the 00:04:00.440 --> 00:04:03.550 constituents of the solute is already present. 00:04:03.550 --> 00:04:07.450 So today I want to talk about a subset of solutions, and in 00:04:07.450 --> 00:04:09.410 particular, I want to talk about acids and bases. 00:04:09.410 --> 00:04:12.230 And this is important, not only in materials processing, 00:04:12.230 --> 00:04:13.747 but we're going to have to understand this if we're going 00:04:13.747 --> 00:04:17.040 to go forward later and talk about biochemistry. 00:04:17.040 --> 00:04:19.100 So, you know, they're around us everywhere. 00:04:19.100 --> 00:04:21.060 You know, you probably got up this morning, you washed your 00:04:21.060 --> 00:04:23.980 hair with a pH-balanced shampoo, maybe had orange 00:04:23.980 --> 00:04:27.460 juice or grapefruit juice with citric and ascorbic acid. 00:04:27.460 --> 00:04:30.600 Your radio is powered by zinc alkaline batteries. 00:04:30.600 --> 00:04:34.400 I started my car, it's got the lead acid battery in it, and 00:04:34.400 --> 00:04:36.450 electricity for all my appliances came from 00:04:36.450 --> 00:04:39.020 coal-fired power plants, spewing out SO2, 00:04:39.020 --> 00:04:40.590 turning out acid rain. 00:04:40.590 --> 00:04:41.580 So we're off to a good start! 00:04:41.580 --> 00:04:43.260 It's Friday. 00:04:43.260 --> 00:04:45.000 So now we want to go back and understand 00:04:45.000 --> 00:04:46.230 this from the beginning. 00:04:46.230 --> 00:04:48.135 So we're going to start with a history lesson. 00:04:48.135 --> 00:04:51.520 And the history lesson starts in ancient times. 00:04:51.520 --> 00:04:56.350 Acids were known all the way back in early times for 00:04:56.350 --> 00:04:59.856 processing of food and materials. 00:05:07.790 --> 00:05:10.530 So who among us hasn't eaten something 00:05:10.530 --> 00:05:11.600 that has been pickled? 00:05:11.600 --> 00:05:16.130 Pickle means to have been processed in acid solution. 00:05:16.130 --> 00:05:20.890 In fact, the word acid comes from the word acidus in Latin, 00:05:20.890 --> 00:05:24.265 and acidus means either sour or tart. 00:05:27.330 --> 00:05:32.360 But the modern chemistry of acids and bases starts with 00:05:32.360 --> 00:05:38.475 Lavoisier in France in 1779. 00:05:38.475 --> 00:05:42.260 And I'm going to be naming many scientists from different 00:05:42.260 --> 00:05:44.180 countries today, so I'm going to use the 00:05:44.180 --> 00:05:45.800 international symbol. 00:05:45.800 --> 00:05:48.310 You know, these ovals that you put on the back of the car, so 00:05:48.310 --> 00:05:50.360 now if you see a car with this on it, you know 00:05:50.360 --> 00:05:51.970 it's a French registry. 00:05:51.970 --> 00:05:54.140 So he's probably got a Peugeot, and he's driving 00:05:54.140 --> 00:05:55.500 around with his Peugeot. 00:05:55.500 --> 00:05:59.640 And what Lavoisier said, in trying to understand acids and 00:05:59.640 --> 00:06:00.680 bases, is-- 00:06:00.680 --> 00:06:03.290 it's a really interesting story. 00:06:03.290 --> 00:06:06.997 He said that oxygen is present in all acids. 00:06:17.650 --> 00:06:18.780 And why? 00:06:18.780 --> 00:06:21.500 Because he spent most of his career studying combustion, so 00:06:21.500 --> 00:06:24.510 he was very concerned about oxygen. 00:06:24.510 --> 00:06:30.240 And the interesting thing is that oxygen, the name of the 00:06:30.240 --> 00:06:34.920 gas, oxygen, actually comes from the greek oxy, which 00:06:34.920 --> 00:06:39.380 means sharp, and, you know, the particle gen, as in to 00:06:39.380 --> 00:06:41.290 generate or to be born. 00:06:41.290 --> 00:06:42.540 OK? 00:06:44.120 --> 00:06:49.540 So it's interesting that this gas is named incorrectly. 00:06:49.540 --> 00:06:55.110 It's named for an attribute that is ascribed to acid, and 00:06:55.110 --> 00:06:57.210 it's wrong. 00:06:57.210 --> 00:06:58.710 And it's in other languages, too. 00:06:58.710 --> 00:07:01.890 The word oxygen translates into other languages as 00:07:01.890 --> 00:07:04.340 meaning something sharp, and it has nothing to do with it. 00:07:04.340 --> 00:07:07.500 But while we're on the topic of Lavoisier, Lavoisier did 00:07:07.500 --> 00:07:10.030 study oxygen. 00:07:10.030 --> 00:07:15.620 And there was an intense rivalry between Lavoisier in 00:07:15.620 --> 00:07:21.950 France, Joseph Priestley in Britain, 00:07:21.950 --> 00:07:26.000 and Scheele in Sweden. 00:07:26.000 --> 00:07:29.460 And all three of them were working simultaneously to 00:07:29.460 --> 00:07:33.680 study combustion and understand oxygen. 00:07:33.680 --> 00:07:35.970 And here I've got a very nice image. 00:07:35.970 --> 00:07:40.290 This is a portrait of Lavoisier with his wife. 00:07:40.290 --> 00:07:42.440 And it's hard to see. 00:07:42.440 --> 00:07:45.460 If the lights were a little bit dimmer, you'd see-- 00:07:45.460 --> 00:07:48.540 notice here, you see all of this chemical apparatus. 00:07:48.540 --> 00:07:53.400 There is bell jars, and various glass apparatus. 00:07:53.400 --> 00:07:57.270 His wife was his partner in the laboratory. 00:07:57.270 --> 00:07:59.350 She was unique among French women in 00:07:59.350 --> 00:08:01.920 that she read English. 00:08:01.920 --> 00:08:05.600 And in his rivalry with Priestley, he relied on his 00:08:05.600 --> 00:08:08.660 wife in order to read Priestley's writings. 00:08:08.660 --> 00:08:09.530 So they worked together. 00:08:09.530 --> 00:08:12.960 She even helped him in the laboratory. 00:08:12.960 --> 00:08:17.020 They married at the time he was 27 and she was 13, and 00:08:17.020 --> 00:08:17.720 they were-- 00:08:17.720 --> 00:08:18.960 what are you so shocked about? 00:08:18.960 --> 00:08:23.650 It's France, and it's 1779! 00:08:23.650 --> 00:08:24.580 Get over it! 00:08:24.580 --> 00:08:28.720 Anyways, she helped him a lot, and we'll say a little bit 00:08:28.720 --> 00:08:32.590 more about that later. 00:08:32.590 --> 00:08:32.930 OK. 00:08:32.930 --> 00:08:36.370 So now let's go on to the next part of the history lesson. 00:08:36.370 --> 00:08:39.740 So so far, we've got one explanation, and it's wrong. 00:08:39.740 --> 00:08:42.340 So let's go to the next one, and we'll go to Britain. 00:08:42.340 --> 00:08:47.230 Sir Humphry Davy in London in 1810. 00:08:47.230 --> 00:08:50.240 So we'll put GB here, and he's driving around in his little 00:08:50.240 --> 00:08:51.740 Jaguar, I suspect. 00:08:51.740 --> 00:08:53.560 And he said something that was correct. 00:08:53.560 --> 00:08:57.000 He said that it's hydrogen present in all acids. 00:09:02.760 --> 00:09:03.750 And that was pretty much it. 00:09:03.750 --> 00:09:06.290 He was a great scientist, did some very good work, but 00:09:06.290 --> 00:09:08.450 really didn't do anything quantitative here. 00:09:08.450 --> 00:09:11.600 So for the quantitative stuff, we have to wait for almost the 00:09:11.600 --> 00:09:12.980 end of the century. 00:09:12.980 --> 00:09:15.240 And we go up to Sweden again, to Arrhenius. 00:09:15.240 --> 00:09:19.590 And Arrhenius, in 1887-- 00:09:19.590 --> 00:09:21.300 so I'll give him a Volvo. 00:09:21.300 --> 00:09:26.750 And he said that the acid is a substance that disassociates 00:09:26.750 --> 00:09:28.740 to produce protons. 00:09:28.740 --> 00:09:37.940 So the acid is defined as a solution that dissociates to 00:09:37.940 --> 00:09:40.410 give protons. 00:09:40.410 --> 00:09:44.540 I'm going to say H plus, meaning the hydrogen ion, or P 00:09:44.540 --> 00:09:47.770 plus, and we're going to keep using the term proton. 00:09:47.770 --> 00:09:50.560 I'm not going to say hydrogen ion, I'm going to say proton. 00:09:50.560 --> 00:09:51.890 So proton in solution. 00:09:51.890 --> 00:09:53.370 So this is what he defines. 00:09:53.370 --> 00:09:55.270 And he further defines the base. 00:09:55.270 --> 00:09:58.800 He defines the base as the complement to the acid. 00:09:58.800 --> 00:10:02.420 And he says that the base is something that dissociates to 00:10:02.420 --> 00:10:04.360 give us hydroxyl. 00:10:04.360 --> 00:10:12.380 The base dissociates to give OH minus the hydroxyl. 00:10:12.380 --> 00:10:17.220 And so now we've got this whole concept of electrolytic 00:10:17.220 --> 00:10:21.530 disassociation, which is what wins him the Nobel prize in 00:10:21.530 --> 00:10:23.690 1903 for this thing. 00:10:23.690 --> 00:10:27.800 And then we saw last day how the addition of ions to water 00:10:27.800 --> 00:10:29.050 gives charge carriers. 00:10:29.050 --> 00:10:33.350 And so the presence of protons and hydroxyl is, in fact, the 00:10:33.350 --> 00:10:37.350 way we have any charge carried through water. 00:10:37.350 --> 00:10:40.450 So up until now, when I said electrical conductivity, we 00:10:40.450 --> 00:10:43.830 were pretty much referring to electronic conductivity. 00:10:43.830 --> 00:10:46.740 But there's a second kind of conductivity, and we can have 00:10:46.740 --> 00:10:49.500 ionic conductivity. 00:10:49.500 --> 00:10:52.900 Ionic conductivity, as the name implies, is not by 00:10:52.900 --> 00:10:54.730 electrons, but by ions. 00:10:54.730 --> 00:10:56.915 And this is typically ions in solution. 00:11:00.190 --> 00:11:03.820 Ionic conductivity in solution, and a solution that 00:11:03.820 --> 00:11:06.165 is an ionic conductor is called an electrolyte. 00:11:08.910 --> 00:11:10.740 So we have electrolyte in our bodies, 00:11:10.740 --> 00:11:14.290 saline, about 5% chloride. 00:11:14.290 --> 00:11:16.730 We have electrolyte in batteries that are ionically 00:11:16.730 --> 00:11:17.930 conductive. 00:11:17.930 --> 00:11:23.160 And the term simply means, we have conduction by ions. 00:11:23.160 --> 00:11:27.390 And so it was the theory of electrolytic dissociation that 00:11:27.390 --> 00:11:30.030 won the Nobel prize. 00:11:30.030 --> 00:11:32.260 So how does this work? 00:11:32.260 --> 00:11:36.230 So we can start with something like HCl gas. 00:11:36.230 --> 00:11:39.540 I'm going to dissolve it in water, and this will give me 00:11:39.540 --> 00:11:41.155 proton, H plus. 00:11:41.155 --> 00:11:44.940 And I'm going to write aq, meaning that it's dissolved in 00:11:44.940 --> 00:11:50.120 water, and the chloride ion, also dissolved in water. 00:11:50.120 --> 00:11:52.920 And so this gives me an acid. 00:11:52.920 --> 00:11:55.130 This is a proton donor. 00:11:55.130 --> 00:11:56.030 And now let's look at 00:11:56.030 --> 00:11:58.380 something like sodium hydroxide. 00:11:58.380 --> 00:12:00.800 Sodium hydroxide at room temperature is an ionic 00:12:00.800 --> 00:12:05.440 compound, so it is a solid, but it is soluble in a polar, 00:12:05.440 --> 00:12:13.420 hydrogen-bonded liquid, so H20, to give hydroxyl aqueous 00:12:13.420 --> 00:12:16.700 plus sodium ion aqueous. 00:12:16.700 --> 00:12:19.270 So again, we see the dissociation. 00:12:19.270 --> 00:12:21.800 And then we can have, from here, a 00:12:21.800 --> 00:12:24.240 neutralization reaction. 00:12:24.240 --> 00:12:26.740 And the neutralization reaction is simply 00:12:26.740 --> 00:12:29.520 reconstitution of the solvent. 00:12:29.520 --> 00:12:33.870 So neutralization, another way to think about it, because 00:12:33.870 --> 00:12:36.300 we're not going to be confined to water by the end of the 00:12:36.300 --> 00:12:40.340 lecture, neutralization is simply a reaction that results 00:12:40.340 --> 00:12:44.230 in reconstitution of the solvents. 00:12:44.230 --> 00:12:46.330 So the solvent, in this case, is water. 00:12:46.330 --> 00:12:48.260 So how would we reconstitute water? 00:12:48.260 --> 00:12:50.520 We combine proton with hydroxyl. 00:12:50.520 --> 00:12:55.110 So let's do that and see the result of that reaction. 00:12:55.110 --> 00:13:00.360 So if I take, and run it in the vertical direction, proton 00:13:00.360 --> 00:13:05.130 plus hydroxyl, we'll give water again-- 00:13:05.130 --> 00:13:07.580 let's give H20 liquid-- 00:13:07.580 --> 00:13:11.080 and now you can see Na plus Cl will give me 00:13:11.080 --> 00:13:14.310 NaCl, aqueous dissolved. 00:13:14.310 --> 00:13:16.590 So this is what you probably learned in your high school 00:13:16.590 --> 00:13:21.230 chemistry, that acid plus base ca give you salt plus water. 00:13:21.230 --> 00:13:24.910 So you see all of this resulting from just the simple 00:13:24.910 --> 00:13:26.640 Arrhenius definition. 00:13:26.640 --> 00:13:27.580 So this is good. 00:13:27.580 --> 00:13:30.800 We've got off to a decent start here with Arrhenius. 00:13:30.800 --> 00:13:34.470 But then the theory has its limitations, as they all do. 00:13:34.470 --> 00:13:36.420 And how do we discover the limitations? 00:13:36.420 --> 00:13:37.860 With some new data. 00:13:37.860 --> 00:13:39.460 So let's look at some data. 00:13:39.460 --> 00:13:45.950 So it had been known for a long time that ammonia, when 00:13:45.950 --> 00:13:50.950 it's dissolved in water, can act as a solution capable of 00:13:50.950 --> 00:13:52.840 neutralizing an acid. 00:13:52.840 --> 00:13:55.780 So if ammonia dissolved in water neutralizes an acid, 00:13:55.780 --> 00:13:56.845 then this must be a base. 00:13:56.845 --> 00:13:59.290 But look, there's no hydroxyl here. 00:13:59.290 --> 00:14:01.910 So the Arrhenius definition of base is inadequate 00:14:01.910 --> 00:14:03.630 to account for this. 00:14:03.630 --> 00:14:04.910 So let's just get that down. 00:14:04.910 --> 00:14:08.750 Ammonia, which you know is a gas at room temperature, will 00:14:08.750 --> 00:14:15.520 neutralize acids. 00:14:15.520 --> 00:14:20.020 But no hydroxyl present. 00:14:20.020 --> 00:14:24.980 So something's going on here that we can't account for by 00:14:24.980 --> 00:14:26.950 the simple Arrhenius definition. 00:14:26.950 --> 00:14:30.020 So to get us out of this conundrum, we had to wait 00:14:30.020 --> 00:14:31.410 until 1923. 00:14:31.410 --> 00:14:34.620 And two scientists simultaneously enunciated the 00:14:34.620 --> 00:14:35.560 same ideas. 00:14:35.560 --> 00:14:37.640 So I'm going to put them both down. 00:14:37.640 --> 00:14:38.680 1923. 00:14:38.680 --> 00:14:44.850 Bronsted, who was in Denmark, and Lowry, who was 00:14:44.850 --> 00:14:46.800 working in the UK. 00:14:46.800 --> 00:14:50.830 Also 1923. 00:14:50.830 --> 00:14:53.380 And I'll give him a Jaguar as well. 00:14:53.380 --> 00:14:56.540 And so the two of them proposed a broader definition 00:14:56.540 --> 00:14:58.790 to account for what's going on here. 00:14:58.790 --> 00:14:59.710 And what did they say? 00:14:59.710 --> 00:15:01.640 They said that acid-- 00:15:01.640 --> 00:15:04.630 they'll keep the same definition as Arrhenius. 00:15:04.630 --> 00:15:07.280 So an acid is going to be a proton donor. 00:15:10.240 --> 00:15:11.300 So that's good. 00:15:11.300 --> 00:15:14.780 Let's even put here, same as Arrhenius. 00:15:18.150 --> 00:15:19.830 But now here's the difference. 00:15:19.830 --> 00:15:24.500 The base is no longer confined to hydroxyl chemistry. 00:15:24.500 --> 00:15:26.710 They call it a proton acceptor. 00:15:30.140 --> 00:15:31.970 And that's different. 00:15:31.970 --> 00:15:35.530 So hydroxyl-free. 00:15:35.530 --> 00:15:37.470 Now, let's be careful here. 00:15:37.470 --> 00:15:39.630 If I propose this new definition, I 00:15:39.630 --> 00:15:40.970 can't throw out hydroxyl. 00:15:40.970 --> 00:15:43.990 So you've got to watch to make sure that by broadening the 00:15:43.990 --> 00:15:46.030 definition, we don't exclude hydroxyl. 00:15:46.030 --> 00:15:49.650 So the theory has to encompass what we already know, and then 00:15:49.650 --> 00:15:53.350 continue to encompass things that tend to contradict what 00:15:53.350 --> 00:15:54.060 we already know. 00:15:54.060 --> 00:15:56.540 So let's take a look at what this gives us. 00:15:56.540 --> 00:16:01.750 So I'm going to write a broader equation here. 00:16:01.750 --> 00:16:06.180 I'm going to write this as the acid. 00:16:06.180 --> 00:16:07.290 So what do I have? 00:16:07.290 --> 00:16:10.180 I have every acid has to have a proton in 00:16:10.180 --> 00:16:12.100 it, plus some residual. 00:16:12.100 --> 00:16:15.380 So I can rewrite the acid in this form. 00:16:15.380 --> 00:16:18.990 I'm going to react it with a base. 00:16:18.990 --> 00:16:21.300 So according to this definition, this has to be a 00:16:21.300 --> 00:16:23.170 proton donor. 00:16:23.170 --> 00:16:25.060 And this, you're going to watch me on this one. 00:16:25.060 --> 00:16:27.390 This is going to be a proton acceptor. 00:16:27.390 --> 00:16:28.690 And we'll put some identities here. 00:16:28.690 --> 00:16:30.520 Eventually we're going to write this with ammonia in it, 00:16:30.520 --> 00:16:32.850 but let's just do the broad definition. 00:16:32.850 --> 00:16:36.200 So what happens is, if this is a proton acceptor, on this 00:16:36.200 --> 00:16:38.820 side of the equation, it takes the proton from here. 00:16:38.820 --> 00:16:40.010 This is the proton donor. 00:16:40.010 --> 00:16:45.130 It gives it away, and we end up with a BH plus. 00:16:45.130 --> 00:16:48.400 So this proton acceptor has accepted the proton, leaving 00:16:48.400 --> 00:16:52.660 behind the deprotonated A minus. 00:16:52.660 --> 00:16:54.260 That's a nice little reaction. 00:16:54.260 --> 00:16:57.850 But now, if you'd nodded off for the last 90 seconds, and 00:16:57.850 --> 00:17:01.010 then opened your eyes and said, well, he said acid is a 00:17:01.010 --> 00:17:04.460 proton donor, this thing can give up a proton. 00:17:04.460 --> 00:17:08.090 So OK, I'm going to call this thing a proton donor. 00:17:08.090 --> 00:17:10.410 And this is most certainly a proton acceptor. 00:17:10.410 --> 00:17:12.660 Look, it has accepted the proton. 00:17:12.660 --> 00:17:16.890 So this is going to be a proton acceptor. 00:17:16.890 --> 00:17:20.050 So now I've got in this equation two proton donors and 00:17:20.050 --> 00:17:21.910 two proton acceptors. 00:17:21.910 --> 00:17:23.160 And they're linked. 00:17:23.160 --> 00:17:26.660 This proton donor, BH plus, is linked to B. 00:17:26.660 --> 00:17:30.360 So I'm going to put a little yolk over this one. 00:17:30.360 --> 00:17:34.200 And this HA, the original acid, is linked to 00:17:34.200 --> 00:17:36.630 this base, A minus. 00:17:36.630 --> 00:17:38.425 So I'm going to put a yoke over that. 00:17:41.430 --> 00:17:47.730 And the Latin word for yoke, to yoke, is jugere, from which 00:17:47.730 --> 00:17:50.350 we get the word conjugate. 00:17:50.350 --> 00:17:52.560 So I'm going to call these things 00:17:52.560 --> 00:17:54.665 conjugate acid-base pairs. 00:18:02.050 --> 00:18:04.770 And every equation has two. 00:18:04.770 --> 00:18:06.840 Because you've got a proton donor proton acceptor. 00:18:06.840 --> 00:18:09.130 So now this is, follow the bouncing ball. 00:18:09.130 --> 00:18:11.880 If you want to understand acid-base chemistry, just 00:18:11.880 --> 00:18:12.950 follow the proton. 00:18:12.950 --> 00:18:15.100 Here's proton here, goes over here. 00:18:15.100 --> 00:18:18.980 Here's something deprotonated, now it's protonated. 00:18:18.980 --> 00:18:22.130 That's the rhythm here. 00:18:22.130 --> 00:18:27.250 So the whole thing is, acid-base reactions can be 00:18:27.250 --> 00:18:29.965 defined as a proton transfer reactions. 00:18:33.500 --> 00:18:37.590 Remember we talked about ionicity and electron transfer 00:18:37.590 --> 00:18:40.090 in order to achieve octet stability? 00:18:40.090 --> 00:18:42.140 So we saw the whole life and times of 00:18:42.140 --> 00:18:43.600 electron transfer reactions. 00:18:43.600 --> 00:18:47.470 Now life and times of proton transfer reactions. 00:18:47.470 --> 00:18:47.840 OK. 00:18:47.840 --> 00:18:50.710 And last thing I want to do, is to just make sure that we 00:18:50.710 --> 00:18:52.360 see the definitions. 00:18:52.360 --> 00:18:55.870 You know, all queens are female, but not all females 00:18:55.870 --> 00:18:56.950 are queens. 00:18:56.950 --> 00:18:59.200 So this one here, what's this? 00:18:59.200 --> 00:19:01.840 This is definitely, it's a proton donor. 00:19:01.840 --> 00:19:02.990 So it's an acid. 00:19:02.990 --> 00:19:06.350 So it's definitely an Arrhenius acid, because it's 00:19:06.350 --> 00:19:11.850 got a proton, and it's also a Bronsted-Lowry acid. 00:19:11.850 --> 00:19:14.270 Now, what about this one? 00:19:14.270 --> 00:19:15.510 This is a base. 00:19:15.510 --> 00:19:17.690 It may not have hydroxyl in it. 00:19:17.690 --> 00:19:18.670 May or may not. 00:19:18.670 --> 00:19:22.580 So this is definitely a Bronsted-Lowry base, but I 00:19:22.580 --> 00:19:25.730 can't say for sure that it's an Arrhenius base, because 00:19:25.730 --> 00:19:28.100 Arrhenius has to be O minus. 00:19:28.100 --> 00:19:29.460 This one here, what about this? 00:19:29.460 --> 00:19:33.310 Unless it's OH minus, this one here is, what? 00:19:33.310 --> 00:19:36.950 It's Bronsted-Lowry base. 00:19:36.950 --> 00:19:41.010 And this one here, this can be both Bronsted-Lowry acid and 00:19:41.010 --> 00:19:44.070 it can be an Arrhenius acid. 00:19:44.070 --> 00:19:47.940 So this is how we can differentiate them. 00:19:47.940 --> 00:19:50.400 OK, good. 00:19:50.400 --> 00:19:53.920 Now let's go to the ammonia, see if we've got ourselves out 00:19:53.920 --> 00:19:57.330 of the conundrum so we can write now NH3. 00:19:57.330 --> 00:19:58.920 And I'm going to say that this is ammonia 00:19:58.920 --> 00:20:00.320 that's already dissolved. 00:20:00.320 --> 00:20:04.020 So ammonia is already in aqueous solution, and it 00:20:04.020 --> 00:20:10.170 reacts with water, H20 liquid, to do what? 00:20:10.170 --> 00:20:12.250 This is supposed to be a-- 00:20:12.250 --> 00:20:16.390 if this is a base, remember, this is the thing that we're 00:20:16.390 --> 00:20:17.390 trying to demonstrate. 00:20:17.390 --> 00:20:20.180 If it's a base, according to this, it's a proton acceptor. 00:20:20.180 --> 00:20:22.920 So I'm going to stick a proton on this, and I'm going to get 00:20:22.920 --> 00:20:26.450 NH4 plus the ammonium ion. 00:20:29.010 --> 00:20:30.940 And how did I get the ammonium ion? 00:20:30.940 --> 00:20:36.950 I took a proton from water, leaving behind OH. 00:20:36.950 --> 00:20:39.480 So can you see that how this thing works? 00:20:39.480 --> 00:20:43.430 By gobbling up protons, by becoming a proton vacuum 00:20:43.430 --> 00:20:48.020 cleaner, it takes protons out of water, leaving 00:20:48.020 --> 00:20:49.630 an excess of hydroxyl. 00:20:49.630 --> 00:20:52.710 And in effect, now we've got something that's tantamount to 00:20:52.710 --> 00:20:54.030 an Arrhenius base. 00:20:54.030 --> 00:20:55.930 But it all started off with this. 00:20:55.930 --> 00:20:57.760 So now we can link these two. 00:20:57.760 --> 00:21:02.300 I'm going to yoke ammonium and ammonia as conjugate 00:21:02.300 --> 00:21:05.280 acid-base, and there is water and hydroxyl 00:21:05.280 --> 00:21:06.850 as acid-base pairs. 00:21:06.850 --> 00:21:10.770 So again, let's get the colors going. 00:21:10.770 --> 00:21:12.460 Here we've got Bronsted-Lowry-- 00:21:12.460 --> 00:21:14.380 the bases are always going to be in blue. 00:21:14.380 --> 00:21:16.340 Blue and base both begin with the letter B. 00:21:16.340 --> 00:21:19.950 So this is definitely Brosted-Lowry base, but it's 00:21:19.950 --> 00:21:22.110 not an Arrhenius base. 00:21:22.110 --> 00:21:26.100 This is a Bronsted-Lowry base, and it's also 00:21:26.100 --> 00:21:28.570 an Arrhenius base. 00:21:28.570 --> 00:21:31.160 This one here, we can call this one-- 00:21:31.160 --> 00:21:35.000 in this case, it's a proton donor, so it's both an 00:21:35.000 --> 00:21:37.880 Arrhenius acid and a Bronsted-Lowry acid. 00:21:37.880 --> 00:21:38.760 But look at this. 00:21:38.760 --> 00:21:41.740 You'd say, OK, I know what he's doing. 00:21:41.740 --> 00:21:44.760 Arrheius, Bronsted-Lowry, Arrhenius, Bronsted-Lowry. 00:21:44.760 --> 00:21:47.170 This is Bronsted-Lowry only, this must be 00:21:47.170 --> 00:21:48.420 Bronsted-Lowry only. 00:21:48.420 --> 00:21:49.070 But look! 00:21:49.070 --> 00:21:51.540 This is a proton donor. 00:21:51.540 --> 00:21:53.100 It dissociates to give protons. 00:21:53.100 --> 00:21:57.420 So this is both Bronsted-Lowry and Arrhenius. 00:21:57.420 --> 00:21:59.640 Most people will miss that. 00:21:59.640 --> 00:22:03.410 We'll get to see, maybe, on a subsequent celebration, how 00:22:03.410 --> 00:22:05.370 many of you miss that. 00:22:05.370 --> 00:22:05.680 OK. 00:22:05.680 --> 00:22:06.330 So. 00:22:06.330 --> 00:22:08.570 So now, let's go into the chemistry here. 00:22:08.570 --> 00:22:11.730 Because I said up here at the beginning of the lecture-- 00:22:11.730 --> 00:22:14.740 what is it-- bonding is the key to understanding. 00:22:14.740 --> 00:22:18.030 So what is it about bonding here that defines the 00:22:18.030 --> 00:22:19.310 Bronsted-Lowry base? 00:22:19.310 --> 00:22:23.240 So I'm going to write this reaction in this way, now. 00:22:23.240 --> 00:22:25.810 I'm going to put-- here's the proton, which 00:22:25.810 --> 00:22:27.220 is coming from water. 00:22:27.220 --> 00:22:29.290 And I'm going to write that with NH3. 00:22:29.290 --> 00:22:31.610 I'm going to use the Lewis structure. 00:22:31.610 --> 00:22:35.730 So, you know, Lewis structure looks like this, Nitrate has 00:22:35.730 --> 00:22:39.380 got five valence electrons, three of them are bound, and 00:22:39.380 --> 00:22:41.010 now I've got this long pair. 00:22:41.010 --> 00:22:45.580 So what do we know about the electronic 00:22:45.580 --> 00:22:46.960 structure of proton? 00:22:46.960 --> 00:22:47.770 What does it look like? 00:22:47.770 --> 00:22:49.020 What's the Lewis structure of proton? 00:22:52.080 --> 00:22:54.480 How many electrons on proton? 00:22:54.480 --> 00:22:54.900 None. 00:22:54.900 --> 00:22:56.680 This is nothing. 00:22:56.680 --> 00:22:59.520 This is very needy. 00:22:59.520 --> 00:23:02.910 It's like the neediest friend you have. You know, the one 00:23:02.910 --> 00:23:05.530 that's always taking stuff from you, taking your 00:23:05.530 --> 00:23:08.950 emotional energy, giving back nothing? 00:23:08.950 --> 00:23:10.180 That's proton. 00:23:10.180 --> 00:23:12.100 That's the human equivalent of proton. 00:23:12.100 --> 00:23:17.310 So if proton wants to make a bond to form NH4, proton is 00:23:17.310 --> 00:23:22.590 going to come over here and exploit both electrons. 00:23:22.590 --> 00:23:26.700 So if this is going to be a proton acceptor, the only way 00:23:26.700 --> 00:23:30.000 it can be a proton acceptor is to have two 00:23:30.000 --> 00:23:32.130 unused electrons available. 00:23:32.130 --> 00:23:34.520 This is going to be a dative bond, agreed? 00:23:34.520 --> 00:23:37.450 Dative, because both electrons from the bond 00:23:37.450 --> 00:23:38.780 come from the nitrogen. 00:23:38.780 --> 00:23:41.510 The proton doesn't contribute anything. 00:23:41.510 --> 00:23:43.060 So that's the hallmark. 00:23:43.060 --> 00:23:49.900 The proton acceptor axiomatically must have an 00:23:49.900 --> 00:23:53.480 available non-bonding pair. 00:23:53.480 --> 00:23:59.660 So wherever you see non-bonding pairs, wherever 00:23:59.660 --> 00:24:03.010 you see a compound that has this capability, it could 00:24:03.010 --> 00:24:07.870 serve as a Bronsted-Lowry base. 00:24:07.870 --> 00:24:12.140 We know that water, because it has hydroxyl in it, has to 00:24:12.140 --> 00:24:12.910 satisfy this. 00:24:12.910 --> 00:24:13.970 So let's take a look. 00:24:13.970 --> 00:24:16.940 H20 we can do similarly. 00:24:16.940 --> 00:24:18.190 Oxygen. 00:24:18.190 --> 00:24:21.050 It's got 6 electrons, 2 are in the, bonds and we have 2 00:24:21.050 --> 00:24:22.520 non-bonding pairs. 00:24:22.520 --> 00:24:26.380 So then when we attach proton here, we make 00:24:26.380 --> 00:24:29.050 something called hydronium. 00:24:29.050 --> 00:24:32.390 We make hydronium ion. 00:24:32.390 --> 00:24:34.750 So it's a little fancier than just saying, I've got this 00:24:34.750 --> 00:24:37.960 naked proton with no electrons swimming around in water. 00:24:37.960 --> 00:24:41.340 In fact, it's more coordinated like this. 00:24:41.340 --> 00:24:44.180 H30 plus, and while we're in the neighborhood, we 00:24:44.180 --> 00:24:44.870 might as well show. 00:24:44.870 --> 00:24:46.930 This is sp3 hybridized. 00:24:46.930 --> 00:24:51.190 We've got one, two, three, four orbitals. 00:24:51.190 --> 00:24:52.560 Hydrogen's on three. 00:24:52.560 --> 00:24:56.180 It's got a net charge of plus 1, and lone pair 00:24:56.180 --> 00:24:57.620 on the fourth side. 00:24:57.620 --> 00:25:01.680 So there's the structure of hydronium. 00:25:01.680 --> 00:25:04.310 And we can now write the equation. 00:25:04.310 --> 00:25:14.050 We can say H20 liquid plus H20 liquid gives me H3O 00:25:14.050 --> 00:25:18.520 plus, plus OH minus. 00:25:18.520 --> 00:25:22.520 So this is now the self-ionization or 00:25:22.520 --> 00:25:23.720 self-dissociation reaction. 00:25:23.720 --> 00:25:26.520 So now I can pair these as well. 00:25:26.520 --> 00:25:28.540 I can yoke these. 00:25:28.540 --> 00:25:29.890 I have acid-base pair. 00:25:29.890 --> 00:25:36.100 So this is acid here, and the conjugate base is water, H20. 00:25:36.100 --> 00:25:39.180 Hydroxyl, we know, has to be a base, and its 00:25:39.180 --> 00:25:41.720 conjugate acid is water. 00:25:41.720 --> 00:25:44.100 So you see, in the same equation, same place, same 00:25:44.100 --> 00:25:48.340 time, water is acting as both acid and base relative to 00:25:48.340 --> 00:25:50.440 these two species. 00:25:50.440 --> 00:25:55.080 And so we call such a such a compound that acts as both 00:25:55.080 --> 00:25:57.360 acid and base, we call it amphipathic. 00:26:01.930 --> 00:26:04.310 Has two moods. 00:26:04.310 --> 00:26:06.082 You know, amphi, like in amphitheater. 00:26:06.082 --> 00:26:07.870 Have you ever seen a Roman theater? 00:26:07.870 --> 00:26:09.575 It looks like this from the top down. 00:26:09.575 --> 00:26:12.410 It's got all this, you know, like this, and all the people 00:26:12.410 --> 00:26:14.690 are here, and there's the stage up here. 00:26:14.690 --> 00:26:22.440 But if I make a theater in the round, that is amphitheater. 00:26:22.440 --> 00:26:26.120 Or as it's commonly mispronounced, ampitheater. 00:26:26.120 --> 00:26:28.750 3091ers do not say ampitheater, they say 00:26:28.750 --> 00:26:29.810 amphitheater. 00:26:29.810 --> 00:26:33.130 So this reaction here is self-dissociation. 00:26:33.130 --> 00:26:33.400 Right? 00:26:33.400 --> 00:26:38.300 This reaction is self-dissociation of water. 00:26:38.300 --> 00:26:41.980 Or because we're forming ions, it's also called 00:26:41.980 --> 00:26:43.230 self-ionization. 00:26:48.260 --> 00:26:51.110 Self-dissociation or self-ionization of water. 00:26:51.110 --> 00:26:55.710 Now, turns out that the chemical's power of H3O plus 00:26:55.710 --> 00:26:57.620 and OH minus is very high. 00:26:57.620 --> 00:27:00.350 So this reaction doesn't go very far to the right. 00:27:00.350 --> 00:27:04.690 The amount of the dissociation is tiny, and to be specific, 00:27:04.690 --> 00:27:09.790 at 25 degrees C, the amount of, if you take deionized, 00:27:09.790 --> 00:27:13.530 deaerated water, absolutely pure and pristine. 00:27:13.530 --> 00:27:18.120 The amount of native H30 plus and OH minus is on the order 00:27:18.120 --> 00:27:21.020 of one part in 10 million. 00:27:21.020 --> 00:27:24.520 So H3O plus concentration would be 10 00:27:24.520 --> 00:27:26.910 to the minus 7 molar. 00:27:26.910 --> 00:27:29.810 And obviously, from the stoichiometry of the equation, 00:27:29.810 --> 00:27:34.910 you get the identical amount of OH minus. 00:27:34.910 --> 00:27:37.740 Well, that's in the self-dissociation. 00:27:37.740 --> 00:27:41.490 And so you have very, very few charge carriers, which is why 00:27:41.490 --> 00:27:46.090 high-purity water is a very poor conductor of electricity, 00:27:46.090 --> 00:27:48.140 even as an electrolyte. 00:27:48.140 --> 00:27:50.550 And that's, I've told you in the past, that could be one 00:27:50.550 --> 00:27:52.390 indicator of certain toxins. 00:27:52.390 --> 00:27:54.550 If you measure the conductivity of water and you 00:27:54.550 --> 00:27:57.390 discover it's abnormally high, and it's putatively supposed 00:27:57.390 --> 00:28:00.460 to be pure water, that's an indication that 00:28:00.460 --> 00:28:01.320 it's not pure water. 00:28:01.320 --> 00:28:03.380 There's some other charge carriers present. 00:28:03.380 --> 00:28:09.880 So we can write a Ksp we analogy. 00:28:09.880 --> 00:28:13.200 And it's called the water ionization constant, which is 00:28:13.200 --> 00:28:18.700 the product H3O plus and OH minus. 00:28:18.700 --> 00:28:20.680 And you can do the math. 00:28:20.680 --> 00:28:23.480 That's 10 to the minus 14 is the product. 00:28:23.480 --> 00:28:27.310 And you can use the common ion effect here. 00:28:27.310 --> 00:28:29.960 If I introduce some other acid, look at how this 00:28:29.960 --> 00:28:32.670 equation helps you the same way that Ksp did. 00:28:32.670 --> 00:28:36.460 If I have acid, in other words, protons donated from 00:28:36.460 --> 00:28:39.180 some other source, that means this number is going to be 00:28:39.180 --> 00:28:41.000 higher than 10 to the minus 7. 00:28:41.000 --> 00:28:43.470 If this number is higher than 10 to the minus 7, and the 00:28:43.470 --> 00:28:47.200 product must be 10 to the minus 14, this must be lower. 00:28:47.200 --> 00:28:53.950 So when I have, H3O plus goes up, then OH minus must go 00:28:53.950 --> 00:28:56.650 down, and under these circumstances, we have 00:28:56.650 --> 00:28:58.960 something that is called proton-rich. 00:29:02.060 --> 00:29:06.240 And we call this acid, simply because the proton 00:29:06.240 --> 00:29:08.370 concentration exceeds the hydroxyl. 00:29:08.370 --> 00:29:10.630 And likewise for the other. 00:29:10.630 --> 00:29:15.480 And so we can make a plot of this, and that's shown here. 00:29:15.480 --> 00:29:19.440 And all we've got is OH versus H3O plus. 00:29:19.440 --> 00:29:23.540 And you can see that it's a right hyperbola. 00:29:23.540 --> 00:29:27.610 But it goes back to that comment that I made in the 00:29:27.610 --> 00:29:29.900 past about how you graph data. 00:29:29.900 --> 00:29:33.030 I don't know what to do with that, because it's curved. 00:29:33.030 --> 00:29:36.330 I can't tell whether the data are good or bad. 00:29:36.330 --> 00:29:40.330 So instead of looking at something like this, y versus 00:29:40.330 --> 00:29:43.890 x, I want to transform so that can get a straight line. 00:29:43.890 --> 00:29:46.720 Because then I can make a judgment about goodness 00:29:46.720 --> 00:29:47.780 of fit and so on. 00:29:47.780 --> 00:29:52.870 So I need some f of x versus g of y to, quote unquote, 00:29:52.870 --> 00:29:53.930 straighten this out. 00:29:53.930 --> 00:29:59.540 And we have that, thanks to another Dane, 00:29:59.540 --> 00:30:01.930 by the name of Sorensen. 00:30:01.930 --> 00:30:05.050 Sorensen was the one that gave us another way 00:30:05.050 --> 00:30:06.810 to think about it. 00:30:06.810 --> 00:30:13.590 Sorensen, who in 1901, and he's got the DK on his-- 00:30:13.590 --> 00:30:14.830 he's probably got a Volvo, too. 00:30:14.830 --> 00:30:16.520 Or maybe he's driving a Saab. 00:30:16.520 --> 00:30:19.620 So he was a biochemist at the Carlsberg brewery. 00:30:19.620 --> 00:30:22.930 Yes, they had biochemists, because they wanted understand 00:30:22.930 --> 00:30:25.670 the chemistry of beer production. 00:30:25.670 --> 00:30:26.570 What a concept. 00:30:26.570 --> 00:30:27.850 Having people that understand the 00:30:27.850 --> 00:30:29.960 technology of the business. 00:30:29.960 --> 00:30:32.580 So he was working at the Carlsberg brewery, and he 00:30:32.580 --> 00:30:37.390 decided to take this acid-base business and turn it into 00:30:37.390 --> 00:30:41.810 something that's much more readily recognizable. 00:30:41.810 --> 00:30:49.030 And so he defined a concept called the chemical potential, 00:30:49.030 --> 00:30:53.850 which, if you like, is the reactivity, the chemical 00:30:53.850 --> 00:30:55.250 potential of hydronium. 00:30:58.720 --> 00:30:59.980 And he gave it the symbol. 00:30:59.980 --> 00:31:04.950 Lowercase p for potential, and uppercase H as, obviously, for 00:31:04.950 --> 00:31:06.790 the hydrogen ion. 00:31:06.790 --> 00:31:09.970 And he said, I'm going to make this a logarithm. 00:31:09.970 --> 00:31:12.820 So it's logarithm, and in those days, everybody was 00:31:12.820 --> 00:31:17.780 using slide rules, so it's log base 10 of the concentration 00:31:17.780 --> 00:31:19.010 of hydronium. 00:31:19.010 --> 00:31:21.650 And being a good engineer, he recognized since this starts 00:31:21.650 --> 00:31:26.050 off at 10 to the minus 7, the log of a number less than one 00:31:26.050 --> 00:31:27.930 is going to be negative. 00:31:27.930 --> 00:31:29.700 And who wants to deal with negative numbers? 00:31:29.700 --> 00:31:31.260 So you put a minus sign here. 00:31:31.260 --> 00:31:34.610 That way, pH normally is a positive number. 00:31:34.610 --> 00:31:39.020 And now you can see the results of Sorensen's 00:31:39.020 --> 00:31:40.585 straightening things out for us. 00:31:40.585 --> 00:31:43.220 So now you go over a wider range, and you can see, you 00:31:43.220 --> 00:31:45.220 have nice straight line relationship, and then you can 00:31:45.220 --> 00:31:47.040 get data on there, and so on. 00:31:47.040 --> 00:31:49.990 And this is taken from your book, and it shows the pH 00:31:49.990 --> 00:31:52.830 values of some common substances. 00:31:52.830 --> 00:31:56.690 If you start here at neutral pH 7, you have milk, you have 00:31:56.690 --> 00:32:00.650 human blood, normal things that you would expect, fluids 00:32:00.650 --> 00:32:02.950 and so on, are hovering around 7. 00:32:02.950 --> 00:32:04.690 If you take some coffee, you're going to go into the 00:32:04.690 --> 00:32:05.370 acidic region. 00:32:05.370 --> 00:32:07.780 You see tomatoes down here at about 4. 00:32:07.780 --> 00:32:12.705 Wine, you'll see in the reviews of wines, they'll say 00:32:12.705 --> 00:32:14.770 it has balanced acidity and so on. 00:32:14.770 --> 00:32:16.830 Yeah, it's down around pH 3. 00:32:16.830 --> 00:32:21.040 And carbonated soft drinks, some of them get down to 2. 00:32:21.040 --> 00:32:23.020 Vinegar is wine that has spoiled. 00:32:23.020 --> 00:32:25.630 Vin aigre, which means eager. 00:32:25.630 --> 00:32:27.140 The Middle French eager meant 00:32:27.140 --> 00:32:29.660 impetuous, or tart, or something. 00:32:29.660 --> 00:32:31.070 So this is spoiled wine. 00:32:31.070 --> 00:32:32.310 And the pH changes. 00:32:32.310 --> 00:32:35.720 So by measuring the pH of wine, you can tell if it's 00:32:35.720 --> 00:32:36.580 changing or not. 00:32:36.580 --> 00:32:37.400 There's lemon juice. 00:32:37.400 --> 00:32:41.840 Gastric juices in the stomach can get down to 1, pH of 1. 00:32:41.840 --> 00:32:43.950 But you want that happening only at one point in the 00:32:43.950 --> 00:32:45.300 digestive cycle. 00:32:45.300 --> 00:32:48.930 If you run around for long periods of time at pH 1, you 00:32:48.930 --> 00:32:51.700 will ulcerate, in other words, you'll puncture the walls. 00:32:51.700 --> 00:32:55.740 And if that's about to happen, you need to neutralize. 00:32:55.740 --> 00:32:56.790 So how do you neutralize? 00:32:56.790 --> 00:32:58.750 You go up with something that has a high pH. 00:32:58.750 --> 00:33:01.200 So you can start with something like Alka-Seltzer, 00:33:01.200 --> 00:33:04.130 sodium bicarbonate at about 8.4, or milk 00:33:04.130 --> 00:33:05.950 of magnesia, 10.5. 00:33:05.950 --> 00:33:07.820 Why is it milk of magnesia? 00:33:07.820 --> 00:33:10.830 From last day, because it's not a solution, it is a 00:33:10.830 --> 00:33:11.700 suspension. 00:33:11.700 --> 00:33:14.320 The magnesia is in suspension. 00:33:14.320 --> 00:33:15.710 The magnesium hydroxide. 00:33:15.710 --> 00:33:18.860 And that's one of those mandatory shake well before 00:33:18.860 --> 00:33:22.330 using, because all the magnesia is on the bottom, and 00:33:22.330 --> 00:33:25.910 you've got this almost clear, colorless liquid on the top. 00:33:25.910 --> 00:33:27.390 So you're just drinking water. 00:33:27.390 --> 00:33:29.960 Not going to help you if you've got stomach pain, but 00:33:29.960 --> 00:33:31.620 gastric juice is down here. 00:33:31.620 --> 00:33:34.180 If you're really desperate, don't reach for ammonia. 00:33:34.180 --> 00:33:36.140 You have to be patient. 00:33:36.140 --> 00:33:39.320 They have to work with milk of magnesia. 00:33:39.320 --> 00:33:39.660 OK. 00:33:39.660 --> 00:33:40.910 So that's the range. 00:33:43.860 --> 00:33:47.520 So what else do we have here? 00:33:47.520 --> 00:33:50.850 Let's take a look. 00:33:50.850 --> 00:33:56.570 So far we've been assuming that when we add acid to the 00:33:56.570 --> 00:33:59.680 system, we get 1 to 1 dissociation. 00:33:59.680 --> 00:34:03.730 So the next message that I want to give you here, is that 00:34:03.730 --> 00:34:05.983 not all acids are of equal strength. 00:34:15.510 --> 00:34:18.890 See, I could look up here and say, well, maybe the reason 00:34:18.890 --> 00:34:22.970 that the lemon juice is down it at 2 and the gastric juices 00:34:22.970 --> 00:34:26.170 are at 1 is simply a concentration effect. 00:34:26.170 --> 00:34:28.790 How much acid was introduced. 00:34:28.790 --> 00:34:31.240 No, there's another explanation for it. 00:34:31.240 --> 00:34:34.670 And that is that certain acids don't fully disassociate. 00:34:34.670 --> 00:34:40.220 So for example, if we look at 1 molar HCl, hydrochloric 00:34:40.220 --> 00:34:44.480 acid, you look at 1 molar hydrochloric acid, that goes 00:34:44.480 --> 00:34:49.880 100% into solution and gives us 1 molar H30 plus. 00:34:49.880 --> 00:34:53.450 So 1 to 1 correspondence between how much hydrochloric 00:34:53.450 --> 00:34:57.760 acid we introduce, and how much 00:34:57.760 --> 00:34:59.760 hydroxyl that we generate. 00:34:59.760 --> 00:35:07.160 So this is total dissociation of the HCl. 00:35:07.160 --> 00:35:10.105 And as a result, we call this a strong acid. 00:35:13.410 --> 00:35:15.890 In contrast, let me show you a weak acid. 00:35:15.890 --> 00:35:18.210 So a weak acid is going to dissolve, but it doesn't 00:35:18.210 --> 00:35:18.880 dissociate. 00:35:18.880 --> 00:35:20.530 So there's really two steps here. 00:35:20.530 --> 00:35:23.160 First you've got to get the stuff in solution, and then 00:35:23.160 --> 00:35:26.330 once you get it in solution, it has to break apart. 00:35:26.330 --> 00:35:29.165 It's possible to go into solution and not break apart. 00:35:29.165 --> 00:35:32.140 In which case, you don't have the protons, but you've got 00:35:32.140 --> 00:35:33.520 the solution. 00:35:33.520 --> 00:35:34.470 That's not an acid. 00:35:34.470 --> 00:35:37.700 So a weak acid would be, let's, in contrast, 00:35:37.700 --> 00:35:39.070 look at a weak acid. 00:35:39.070 --> 00:35:40.930 A weak acid would be something like acetic 00:35:40.930 --> 00:35:44.210 acid, which is CH3COOH. 00:35:44.210 --> 00:35:45.760 And this is for historical reasons. 00:35:45.760 --> 00:35:49.580 Normally, the proton that's going to dissociate is at the 00:35:49.580 --> 00:35:53.890 front of the formula, but this was written long ago, before 00:35:53.890 --> 00:35:55.170 people understood this theory. 00:35:55.170 --> 00:35:57.990 And that's the way you'll see acetic acid written. 00:35:57.990 --> 00:36:02.280 So really, this is the proton, and the CH3COO is really the 00:36:02.280 --> 00:36:06.310 acetate anion, Ac, acetate anion. 00:36:06.310 --> 00:36:10.230 So we're going to put that into solution, like this. 00:36:10.230 --> 00:36:13.140 I'm going to put it into water, H20 liquid. 00:36:13.140 --> 00:36:18.005 So this is the salt out of solution, and all we're going 00:36:18.005 --> 00:36:23.210 to do is make it into the aqueous solution of same COOH, 00:36:23.210 --> 00:36:26.060 and I'm just going to write aq. 00:36:26.060 --> 00:36:28.880 Now, if this were strong acid with impunity, I would write 00:36:28.880 --> 00:36:33.030 whatever the concentration of acetic acid is, I break it 00:36:33.030 --> 00:36:35.400 apart, and I get the full amount of the proton. 00:36:35.400 --> 00:36:44.340 What happens is that this, now plus H20, gives me H3O plus 00:36:44.340 --> 00:36:49.480 plus the remaining acetate, which is CH3COO minus. 00:36:49.480 --> 00:36:53.410 And now, here's where the weakness is manifested. 00:36:53.410 --> 00:36:59.850 The degree to which the acetic acid grabs protons from here, 00:36:59.850 --> 00:37:01.910 and then ends up being protonated, 00:37:01.910 --> 00:37:03.440 is very, very small. 00:37:03.440 --> 00:37:06.310 It turns out that in the case of 1 molar-- 00:37:10.570 --> 00:37:12.360 I'm going to write acetic acid this way, now. 00:37:12.360 --> 00:37:14.100 HAc. 00:37:14.100 --> 00:37:19.880 So this thing here is the CH3COO minus, all right? 00:37:19.880 --> 00:37:25.240 It turns out that in 1 molar acetic acid, we 00:37:25.240 --> 00:37:29.400 get only 0.4% reaction. 00:37:29.400 --> 00:37:33.915 0.4% reacts and dissociates. 00:37:38.180 --> 00:37:44.060 So to give protons, it hangs onto most of its protons. 00:37:44.060 --> 00:37:47.690 So we can then represent this in the form of an acid 00:37:47.690 --> 00:37:49.045 dissociation constant. 00:37:57.850 --> 00:37:58.970 And that it looks like this. 00:37:58.970 --> 00:38:01.730 K sub a for acid. 00:38:01.730 --> 00:38:05.100 So on the right side, what we're going to do is make a 00:38:05.100 --> 00:38:06.460 mass balance here. 00:38:06.460 --> 00:38:08.930 We're going to take the product of the proton, the 00:38:08.930 --> 00:38:14.010 acetate divided by the undisassociated acetic acid. 00:38:14.010 --> 00:38:18.210 So we'll put H3O plus concentration times the 00:38:18.210 --> 00:38:21.690 acetate concentration divided by the 00:38:21.690 --> 00:38:26.350 undissociated HAc aqueous. 00:38:26.350 --> 00:38:31.290 So I'm trying to represent what the ratio is here. 00:38:31.290 --> 00:38:35.890 And instead of being one to one, it's 10 to the minus 5. 00:38:35.890 --> 00:38:37.290 Very, very weak. 00:38:37.290 --> 00:38:39.080 You get a little bit, but not much. 00:38:39.080 --> 00:38:42.260 Now, you could say, well, 10 to the minus 5, this is, just 00:38:42.260 --> 00:38:46.050 for reference, it's 100 times 10 to the minus 7, 00:38:46.050 --> 00:38:47.190 which is the Kw. 00:38:47.190 --> 00:38:50.750 So the point here is, if you put in acetic acid, you'll end 00:38:50.750 --> 00:38:53.590 up with 100 times the proton population that you would have 00:38:53.590 --> 00:38:56.090 had by just self-dissociation. 00:38:56.090 --> 00:38:57.100 So it isn't acid. 00:38:57.100 --> 00:38:58.410 It is donating protons. 00:38:58.410 --> 00:39:01.230 But it's not doing it a lot. 00:39:01.230 --> 00:39:03.610 So this is called a weak acid, because it's 00:39:03.610 --> 00:39:06.635 a poor proton donor. 00:39:09.950 --> 00:39:14.620 And so we can then look at a comparison to, 00:39:14.620 --> 00:39:16.580 say, over here, HCl. 00:39:16.580 --> 00:39:20.370 Let's go back here, and we can write the acid dissociation 00:39:20.370 --> 00:39:23.830 constant for HCl, for the strong acid. 00:39:23.830 --> 00:39:27.280 And in that case, Ka over here, which is going to be the 00:39:27.280 --> 00:39:31.610 H3O plus Cl minus, H3O plus. 00:39:31.610 --> 00:39:35.310 In the case of HCl, we're going to get proton and 00:39:35.310 --> 00:39:44.910 chloride over undissociated HCl dissolved in water. 00:39:44.910 --> 00:39:48.820 And that's 10 to the plus 6, which for all intents and 00:39:48.820 --> 00:39:50.680 purposes is infinity. 00:39:50.680 --> 00:39:55.300 You put in 1 molar HCl, you get 1 molar H plus. 00:39:55.300 --> 00:39:56.210 And look at the ratio. 00:39:56.210 --> 00:39:58.810 10 to the sixth, 10 to the minus 5. 00:39:58.810 --> 00:40:03.770 There's a 10 to the eleventh relationship between the weak 00:40:03.770 --> 00:40:05.890 acid and the strong acid. 00:40:05.890 --> 00:40:09.420 And here's the cartoon that shows this strong acid, put in 00:40:09.420 --> 00:40:12.240 this amount, 100% dissociation, weak acid gives 00:40:12.240 --> 00:40:16.680 you small amounts of proton, and a very weak acid is 00:40:16.680 --> 00:40:19.370 imperceptible amount of disassociation. 00:40:19.370 --> 00:40:21.170 And here's a table that quantifies it. 00:40:21.170 --> 00:40:24.760 So the strong acids up here with the Ka. 00:40:24.760 --> 00:40:28.600 This value of Ka has to be greater than 1, because it's 00:40:28.600 --> 00:40:31.540 saying that we're getting a lot of dissociation, the 00:40:31.540 --> 00:40:32.870 reactions moving to the right. 00:40:32.870 --> 00:40:33.860 And you have these numbers here. 00:40:33.860 --> 00:40:36.360 10 to the ninth, 10 to the eighth, 10 to the sixth. 00:40:36.360 --> 00:40:38.060 Those are differences without distinction. 00:40:38.060 --> 00:40:40.650 if I say the ratio is a million to one, or a billion 00:40:40.650 --> 00:40:43.500 to one, for all intents and purposes, you have 00:40:43.500 --> 00:40:44.610 dissociation. 00:40:44.610 --> 00:40:45.840 And then here are the week acids. 00:40:45.840 --> 00:40:46.070 Look. 00:40:46.070 --> 00:40:47.420 10 to the minus 3. 00:40:47.420 --> 00:40:50.820 There's phosphoric, hydrofluoric, and so on, all 00:40:50.820 --> 00:40:51.400 the way down. 00:40:51.400 --> 00:40:54.140 There's carbonic acid, 10 to the minus 7. 00:40:54.140 --> 00:40:56.890 So there's the list. 00:40:56.890 --> 00:41:01.330 And just another cute demonstration of the 00:41:01.330 --> 00:41:07.330 relationship between bonding and acidity, the acid strength 00:41:07.330 --> 00:41:11.130 increases from left to right, and the bond strength 00:41:11.130 --> 00:41:13.180 increases from right to left. 00:41:13.180 --> 00:41:14.940 You know, HF is very strong. 00:41:14.940 --> 00:41:16.090 It's a hydrogen-bonded. 00:41:16.090 --> 00:41:18.390 Very tight HF bond. 00:41:18.390 --> 00:41:20.620 But what determines if it's going to be a 00:41:20.620 --> 00:41:22.260 strong acid or not? 00:41:22.260 --> 00:41:26.590 It's how willing HF is to give up its H. 00:41:26.590 --> 00:41:28.710 But its H is tightly bound. 00:41:28.710 --> 00:41:32.440 So oddly enough, in HF, you don't give up much of the H. 00:41:32.440 --> 00:41:33.880 HF is over here. 00:41:33.880 --> 00:41:35.170 It's less than one. 00:41:35.170 --> 00:41:36.500 It's a weak acid. 00:41:36.500 --> 00:41:38.310 HCl is a pretty strong acid. 00:41:38.310 --> 00:41:43.020 If you want to go heavy-duty, HBr and HI are even stronger 00:41:43.020 --> 00:41:46.630 acids, because they have a weaker hold on the hydrogen 00:41:46.630 --> 00:41:49.600 within them, so they are much, much more 00:41:49.600 --> 00:41:51.760 generous proton donors. 00:41:51.760 --> 00:41:53.490 So you can see that from there. 00:41:53.490 --> 00:41:54.990 OK. 00:41:54.990 --> 00:41:58.110 So what's the takeaway message here? 00:41:58.110 --> 00:42:07.010 The takeaway message is that equal acid concentration does 00:42:07.010 --> 00:42:08.760 not mean equal acid strength. 00:42:08.760 --> 00:42:11.210 You have to be mediated by the Ka. 00:42:11.210 --> 00:42:14.420 Equal acid concentration, which means, how 00:42:14.420 --> 00:42:16.010 much did you dissolve? 00:42:16.010 --> 00:42:22.510 Does not equal acid strength. 00:42:22.510 --> 00:42:23.510 And what's the reason? 00:42:23.510 --> 00:42:26.140 Because equal acid concentration, this is a 00:42:26.140 --> 00:42:30.090 function of solubility, whereas this is a function of 00:42:30.090 --> 00:42:31.090 dissociation. 00:42:31.090 --> 00:42:34.160 So many dissolve, few dissociate. 00:42:34.160 --> 00:42:34.830 How about that? 00:42:34.830 --> 00:42:37.600 There's a nice tagline you can use. 00:42:37.600 --> 00:42:39.180 Use that at a party this weekend. 00:42:39.180 --> 00:42:41.130 Many dissolve, but few dissociate. 00:42:41.130 --> 00:42:41.450 All right. 00:42:41.450 --> 00:42:43.120 Now I want to go very, very high. 00:42:43.120 --> 00:42:44.590 Big concept, all right? 00:42:44.590 --> 00:42:48.330 Last definition of acid-base comes from the United States. 00:42:48.330 --> 00:42:48.450 G. 00:42:48.450 --> 00:42:48.740 N. 00:42:48.740 --> 00:42:50.820 Lewis. 00:42:50.820 --> 00:42:51.150 Same G. 00:42:51.150 --> 00:42:51.370 N. 00:42:51.370 --> 00:42:55.310 Lewis who gave us the Lewis cross and dot structures, 00:42:55.310 --> 00:42:58.080 covalent bonding, didn't stop inventing. 00:42:58.080 --> 00:43:01.280 So we're going to put U.S.A., with a Chevrolet out in 00:43:01.280 --> 00:43:02.470 California. 00:43:02.470 --> 00:43:03.190 And what did G. 00:43:03.190 --> 00:43:03.430 N. 00:43:03.430 --> 00:43:04.550 Lewis tell us? 00:43:04.550 --> 00:43:08.950 He said, I want to extend the Bronsted-Lowry concept. 00:43:08.950 --> 00:43:10.485 But you know, let me give you an analogy. 00:43:10.485 --> 00:43:12.140 Have you ever stood on a bridge and 00:43:12.140 --> 00:43:14.150 watched the traffic go? 00:43:14.150 --> 00:43:16.750 You see it starts from a stop sign or a traffic light. 00:43:16.750 --> 00:43:20.140 Light turns green, the first car pulls away, the second car 00:43:20.140 --> 00:43:23.020 pulls away, the third car pulls away. 00:43:23.020 --> 00:43:25.370 The other way you can look at it is, when the first car 00:43:25.370 --> 00:43:27.600 pulls away, there's a car vacancy. 00:43:27.600 --> 00:43:31.150 And instead of watching the cars go from right to left, 00:43:31.150 --> 00:43:34.440 watch the car vacancy move from left to right. 00:43:34.440 --> 00:43:35.980 And the two are linked. 00:43:35.980 --> 00:43:39.030 And point of fact, if you're the fourth car from the 00:43:39.030 --> 00:43:40.630 traffic light, light turns green and you 00:43:40.630 --> 00:43:42.350 hit the horn, why? 00:43:42.350 --> 00:43:43.350 You can't drive. 00:43:43.350 --> 00:43:46.020 You have to drive only into a car vacancy, and it takes time 00:43:46.020 --> 00:43:48.130 for the car vacancy to get to you. 00:43:48.130 --> 00:43:52.340 When the rate of vacancy flux is not matched by the rate of 00:43:52.340 --> 00:43:55.340 car flux, then we have a collision, and then we 00:43:55.340 --> 00:43:56.220 exchange papers. 00:43:56.220 --> 00:43:58.570 So it's a mass transport problem. 00:43:58.570 --> 00:43:59.315 So now what G. 00:43:59.315 --> 00:43:59.500 N. 00:43:59.500 --> 00:44:05.620 Lewis said was, instead of looking at this reaction as a 00:44:05.620 --> 00:44:10.470 proton transfer reaction, and looking at proton attachment, 00:44:10.470 --> 00:44:13.680 or proton acquisition, he said, why don't we look at 00:44:13.680 --> 00:44:17.390 this from the other side of the relationship? 00:44:17.390 --> 00:44:20.860 And so he said, let's look at something like, for example, 00:44:20.860 --> 00:44:22.640 we've got NH3 here. 00:44:22.640 --> 00:44:27.910 So let's put the N with the 2 electrons. 00:44:27.910 --> 00:44:31.300 And we've been talking about this from the perspective of 00:44:31.300 --> 00:44:34.980 the bond being formed here through the 00:44:34.980 --> 00:44:37.360 acquisition of the proton. 00:44:37.360 --> 00:44:40.790 Lewis said, I can view this from the other perspective, 00:44:40.790 --> 00:44:42.490 and say, I'm going to view it from the 00:44:42.490 --> 00:44:43.850 perspective of the nitrogen. 00:44:43.850 --> 00:44:46.620 From the perspective of the nitrogen, this reaction 00:44:46.620 --> 00:44:51.690 represents the donation of the electron pair. 00:44:51.690 --> 00:44:53.440 A very high concept. 00:44:53.440 --> 00:44:57.890 So this base is not about proton attachment. 00:44:57.890 --> 00:45:01.390 It's about donating an electronic pair. 00:45:01.390 --> 00:45:04.270 So let's get that down, because that's really good. 00:45:04.270 --> 00:45:08.400 So I'm going to say something that's a base looks like this. 00:45:08.400 --> 00:45:09.840 This is what a base is. 00:45:09.840 --> 00:45:11.920 It's a lone pair. 00:45:11.920 --> 00:45:15.355 This is electron pair, very high level base. 00:45:18.130 --> 00:45:20.900 And what's the proton give us? 00:45:20.900 --> 00:45:22.520 What we're doing, is we're talking about 00:45:22.520 --> 00:45:24.430 electrons and donation. 00:45:24.430 --> 00:45:27.990 So what's this other thing in that same category? 00:45:27.990 --> 00:45:33.740 An electron pair can match up with an empty orbital. 00:45:33.740 --> 00:45:36.110 That's the only place electron pairs can go. 00:45:36.110 --> 00:45:37.840 They go to the empty orbitals. 00:45:37.840 --> 00:45:41.060 So electron pair is a base, and this is just a circle 00:45:41.060 --> 00:45:42.410 around nothing. 00:45:42.410 --> 00:45:42.910 OK? 00:45:42.910 --> 00:45:44.170 This is nothing. 00:45:44.170 --> 00:45:46.050 But it's a special kind of nothing. 00:45:46.050 --> 00:45:47.510 This is called a vacant orbital. 00:45:52.660 --> 00:45:56.150 And I'm going to call a vacant orbital an acid, in the most 00:45:56.150 --> 00:45:57.840 general sense. 00:45:57.840 --> 00:46:00.220 So now I'm going to take an electron pair plus vacant 00:46:00.220 --> 00:46:03.700 orbital, and what did they react to give me? 00:46:03.700 --> 00:46:06.990 Covalent bond. 00:46:06.990 --> 00:46:08.035 You'd expect that from G. 00:46:08.035 --> 00:46:08.240 N. 00:46:08.240 --> 00:46:12.600 Lewis, because G. 00:46:12.600 --> 00:46:12.960 N. 00:46:12.960 --> 00:46:14.570 Lewis enunciated covalency. 00:46:14.570 --> 00:46:15.873 That's why you'd expect it from G. 00:46:15.873 --> 00:46:15.976 N. 00:46:15.976 --> 00:46:16.340 Lewis. 00:46:16.340 --> 00:46:19.750 So this is, vacant orbital plus electron pair gives 00:46:19.750 --> 00:46:20.820 covalent bond. 00:46:20.820 --> 00:46:22.430 Very high level. 00:46:22.430 --> 00:46:23.450 Very high level. 00:46:23.450 --> 00:46:25.190 So what is a base? 00:46:25.190 --> 00:46:31.080 A base is now not just a proton acceptor. 00:46:31.080 --> 00:46:38.040 It's an electron pair donor, and the acid is an electron 00:46:38.040 --> 00:46:39.290 pair acceptor. 00:46:42.100 --> 00:46:44.130 So now there's no chemistry here. 00:46:44.130 --> 00:46:46.280 No chemical identities. 00:46:46.280 --> 00:46:49.190 Which means, I can even go from-- 00:46:49.190 --> 00:46:50.620 I don't even have to be in solution. 00:46:50.620 --> 00:46:52.240 I don't have to be in a liquid. 00:46:52.240 --> 00:46:54.670 This could be a gas and a solid. 00:46:54.670 --> 00:46:56.080 Could be a gas plus a gas. 00:46:56.080 --> 00:46:57.790 So this is, like, Darwinian. 00:46:57.790 --> 00:46:59.940 You know, we've come out of the primordial ooze, and now 00:46:59.940 --> 00:47:03.310 we can fly, because we can talk about any chemical 00:47:03.310 --> 00:47:04.480 reaction we want. 00:47:04.480 --> 00:47:06.820 Any state of matter. 00:47:06.820 --> 00:47:08.590 It's fantastic. 00:47:08.590 --> 00:47:09.680 Absolutely fantastic. 00:47:09.680 --> 00:47:13.210 So here, let me do one last color drawing. 00:47:13.210 --> 00:47:14.990 We want to do this one here. 00:47:14.990 --> 00:47:18.030 This is Lewis and the biggest concept. 00:47:18.030 --> 00:47:19.570 So we're going to go like this. 00:47:19.570 --> 00:47:23.120 Base like this. 00:47:23.120 --> 00:47:26.620 Base with its lone pair hanging out 00:47:26.620 --> 00:47:31.110 plus acid gives us-- 00:47:31.110 --> 00:47:31.760 three colors. 00:47:31.760 --> 00:47:32.370 This is great. 00:47:32.370 --> 00:47:35.100 We've got all this colored chalk, it's Friday, 00:47:35.100 --> 00:47:36.070 what could be better. 00:47:36.070 --> 00:47:37.680 All right. 00:47:37.680 --> 00:47:44.470 So now we're going to end up with A, B, there it is. 00:47:44.470 --> 00:47:46.340 This is the Lewis concept. 00:47:46.340 --> 00:47:53.400 Lewis acid-base concept. 00:47:53.400 --> 00:47:54.310 In the broadest thing. 00:47:54.310 --> 00:47:55.460 Now I'm going to show you an example of 00:47:55.460 --> 00:47:57.090 how you can use this. 00:47:57.090 --> 00:47:58.000 I'm not going to stop here. 00:47:58.000 --> 00:47:59.410 OK, let's go. 00:47:59.410 --> 00:47:59.720 All right. 00:47:59.720 --> 00:48:01.240 So we're going to talk about acid rain 00:48:01.240 --> 00:48:02.870 from burning of coal. 00:48:02.870 --> 00:48:05.210 You know, about half of the electric power in this country 00:48:05.210 --> 00:48:09.930 comes from burning coal, and coal contains about 1% sulfur. 00:48:09.930 --> 00:48:14.290 You can purify it of sulfur, but it takes money to do so. 00:48:14.290 --> 00:48:16.640 A ton of coal will give you about 25 million British 00:48:16.640 --> 00:48:20.130 thermal units, and that's the number in SI units and joules. 00:48:20.130 --> 00:48:23.890 So 3 tons of coal will give you 1 megawatt per day. 00:48:23.890 --> 00:48:26.070 By the way, it takes about one gram of uranium 00:48:26.070 --> 00:48:26.880 to do the same thing. 00:48:26.880 --> 00:48:28.170 So someday, when you're sitting there as a 00:48:28.170 --> 00:48:31.450 policymaker, you've got a choice of 3 tons of coal or 00:48:31.450 --> 00:48:34.290 one gram of uranium, keep this fact in mind. 00:48:34.290 --> 00:48:37.690 A 10 megawatt plant burns 30 tons of coal per day, 00:48:37.690 --> 00:48:41.160 containing a third of a ton of sulphur, which makes 2/3 of a 00:48:41.160 --> 00:48:43.230 ton of SO2. 00:48:43.230 --> 00:48:46.600 And SO2 is a precursor to acid rain. 00:48:46.600 --> 00:48:50.520 Now we can reduce that SO2 emissions by reacting SO2 with 00:48:50.520 --> 00:48:53.140 a lime, CaO, according to this reaction, to 00:48:53.140 --> 00:48:55.610 make calcium sulfite. 00:48:55.610 --> 00:48:58.170 And now I'm going to bring in this. 00:48:58.170 --> 00:48:59.430 Lewis. 00:48:59.430 --> 00:49:02.390 Oh, here's from your textbook, there's the scrubbers with the 00:49:02.390 --> 00:49:05.010 calcium oxide, and water missed, and so on, and 00:49:05.010 --> 00:49:08.810 eventually they trap the SO2. 00:49:08.810 --> 00:49:10.210 They do nothing to the CO2. 00:49:10.210 --> 00:49:13.510 So all the CO2 is going up. 00:49:13.510 --> 00:49:16.060 So here's calcium oxide, which is a solid. 00:49:16.060 --> 00:49:17.100 It's lime. 00:49:17.100 --> 00:49:19.990 You know, stuff you sprinkle on football fields. 00:49:19.990 --> 00:49:22.460 And this is SO2, and it's got this structure with the 00:49:22.460 --> 00:49:24.750 resident bond double single. 00:49:24.750 --> 00:49:27.940 The oxygen here acts the way it did in the 00:49:27.940 --> 00:49:29.490 glasses, as a modifier. 00:49:29.490 --> 00:49:31.580 It goes in and breaks this double bond, and now we have 00:49:31.580 --> 00:49:33.900 three single bonds. 00:49:33.900 --> 00:49:37.090 So we can look at this from Lewis acid-base. 00:49:37.090 --> 00:49:39.960 You know, calcium oxides, electron pair donor. 00:49:39.960 --> 00:49:42.880 If it's an electron pair donor, it's a base. 00:49:42.880 --> 00:49:43.720 So it's a base. 00:49:43.720 --> 00:49:47.250 And you know SO2 better be an acid, or your theory is nuts, 00:49:47.250 --> 00:49:49.340 because SO2 is a precursor to acid rain. 00:49:49.340 --> 00:49:50.670 So it has to be an acid. 00:49:50.670 --> 00:49:52.450 It's an electronic pair acceptor, 00:49:52.450 --> 00:49:53.390 which is what we said. 00:49:53.390 --> 00:49:54.660 It's an electron pair acceptor. 00:49:54.660 --> 00:49:58.020 So this is a Lewis acid-base reaction that 00:49:58.020 --> 00:49:59.770 is a gas-solid reaction. 00:49:59.770 --> 00:50:03.050 So we started with aqueous solutions, and we end up 00:50:03.050 --> 00:50:05.790 generalizing all of these types of reactions. 00:50:05.790 --> 00:50:07.360 So that's pretty good. 00:50:07.360 --> 00:50:12.270 Here's a plot of acid concentration 00:50:12.270 --> 00:50:14.280 up in the sky, here. 00:50:14.280 --> 00:50:17.140 You're Here. 00:50:17.140 --> 00:50:18.410 Yeah. 00:50:18.410 --> 00:50:22.790 Last thing I'll do, I talked a lot about Lavoisier and 00:50:22.790 --> 00:50:24.250 Scheele and Priestley. 00:50:24.250 --> 00:50:26.310 This is a play, if you've got the little bit 00:50:26.310 --> 00:50:27.220 of time this weekend. 00:50:27.220 --> 00:50:28.130 You might try reading it. 00:50:28.130 --> 00:50:30.760 This is Carl Djerassi and Roald Hoffman, both Nobel 00:50:30.760 --> 00:50:32.440 Prize winners in Chemistry. 00:50:32.440 --> 00:50:33.260 Not the same year. 00:50:33.260 --> 00:50:36.340 They won independent Nobel Prizes, and actually speak to 00:50:36.340 --> 00:50:39.010 each other, and they collaborated on this play. 00:50:39.010 --> 00:50:41.000 Here's the setup, the premise. 00:50:41.000 --> 00:50:43.150 The premise of the play is that the Nobel committee 00:50:43.150 --> 00:50:47.380 decides to give Nobel Prizes retrograde. 00:50:47.380 --> 00:50:48.600 Before 1901. 00:50:48.600 --> 00:50:51.740 You see, you can't get a Nobel Prize posthumously. 00:50:51.740 --> 00:50:54.070 You've got to do something great, and you've got to keep 00:50:54.070 --> 00:50:56.670 on living until you get the prize. 00:50:56.670 --> 00:50:58.590 So they decided they're going to go backwards, you know, 00:50:58.590 --> 00:51:01.250 maybe give prizes to people like, I don't know, Maxwell or 00:51:01.250 --> 00:51:02.800 Faraday or whatever. 00:51:02.800 --> 00:51:05.370 And they decide, it should be simple in the old days. 00:51:05.370 --> 00:51:07.790 Because we didn't have all this dog-eat-dog competition 00:51:07.790 --> 00:51:10.530 in science, and big grants, and corporate interests. 00:51:10.530 --> 00:51:11.790 Should be simple. 00:51:11.790 --> 00:51:17.670 Until they hit the Nobel Prize for the discovery of oxygen. 00:51:17.670 --> 00:51:20.000 And then they hit the wall with these three different 00:51:20.000 --> 00:51:21.080 competitors. 00:51:21.080 --> 00:51:24.120 And so the story goes that the three competitors and their 00:51:24.120 --> 00:51:26.440 wives end up in Stockholm, and the 00:51:26.440 --> 00:51:28.100 interactions the take place. 00:51:28.100 --> 00:51:31.350 And it's really fascinating, because you have Lavoisier, 00:51:31.350 --> 00:51:34.260 who was the political conservative but the chemical 00:51:34.260 --> 00:51:39.320 radical, Priestley, who was the chemical radical but the 00:51:39.320 --> 00:51:40.650 political conservative-- 00:51:40.650 --> 00:51:41.710 by the way, Lavoisier. 00:51:41.710 --> 00:51:43.190 You know how he died? 00:51:43.190 --> 00:51:45.800 He was guillotined during the French revolution. 00:51:45.800 --> 00:51:48.630 And people think it's because he was a tax collector. 00:51:48.630 --> 00:51:49.450 Not true. 00:51:49.450 --> 00:51:51.210 He was a tax collector. 00:51:51.210 --> 00:51:55.070 The real reason is Marat, who was one of the chief justices 00:51:55.070 --> 00:51:59.220 of the Jacobin terror, was also a scientist. And around 00:51:59.220 --> 00:52:03.380 1740, Marat had submitted an article for publication, and 00:52:03.380 --> 00:52:04.430 it was rejected. 00:52:04.430 --> 00:52:08.710 And Lavoisier was on the editorial board. 00:52:08.710 --> 00:52:11.910 And so sometimes when I get an article to review, and I have 00:52:11.910 --> 00:52:15.680 to give it a negative review, I think about this story. 00:52:15.680 --> 00:52:19.490 And sometimes, I will just say, you know, I'm really busy 00:52:19.490 --> 00:52:24.060 teaching 3091 and I won't get to this on a timely basis. 00:52:24.060 --> 00:52:24.730 OK, people. 00:52:24.730 --> 00:52:25.980 Have a nice weekend.