1 00:00:00,000 --> 00:00:00,030 2 00:00:00,030 --> 00:00:02,410 The following content is provided under a Creative 3 00:00:02,410 --> 00:00:03,830 Commons license. 4 00:00:03,830 --> 00:00:06,840 Your support will help MIT OpenCourseWare continue to 5 00:00:06,840 --> 00:00:10,510 offer high-quality educational resources for free. 6 00:00:10,510 --> 00:00:13,390 To make a donation or view additional materials from 7 00:00:13,390 --> 00:00:17,190 hundreds of MIT courses, visit MIT OpenCourseWare at 8 00:00:17,190 --> 00:00:18,440 ocw.mit.edu. 9 00:00:18,440 --> 00:00:21,520 10 00:00:21,520 --> 00:00:23,000 PROFESSOR: So a couple of announcements. 11 00:00:23,000 --> 00:00:24,870 Weekly quiz Tuesday. 12 00:00:24,870 --> 00:00:28,450 And also on Tuesday, I want to draw your attention to the 13 00:00:28,450 --> 00:00:31,050 event in the slide. 14 00:00:31,050 --> 00:00:34,340 We have a poster here for a lecture that will occur right 15 00:00:34,340 --> 00:00:39,470 in this room, at 4:00 on Tuesday. 16 00:00:39,470 --> 00:00:41,260 And it's entitled the Wolf Lecture. 17 00:00:41,260 --> 00:00:44,480 The Wolf Lecture was established here about 30 18 00:00:44,480 --> 00:00:47,550 years ago in honor of Professor John Wolf. 19 00:00:47,550 --> 00:00:50,370 John Wolf was an antecedent of mine. 20 00:00:50,370 --> 00:00:53,760 He was the person that invented 3091. 21 00:00:53,760 --> 00:00:59,550 And in 1961, he dared, as a metallurgist, to launch a 22 00:00:59,550 --> 00:01:01,420 variant of freshman chemistry. 23 00:01:01,420 --> 00:01:05,590 And you're the beneficiaries of John Wolf's initiative. 24 00:01:05,590 --> 00:01:11,370 And he also was a spectacular teacher, quite a showman. 25 00:01:11,370 --> 00:01:14,255 And in his honor, they instituted in the Department 26 00:01:14,255 --> 00:01:16,770 of Material Science and Engineering, the Wolf Lecture, 27 00:01:16,770 --> 00:01:21,360 which, as the poster says, is the entire community is 28 00:01:21,360 --> 00:01:24,670 invited to attend, but it's geared towards freshman. 29 00:01:24,670 --> 00:01:28,340 So this is a lecture that the rules are. 30 00:01:28,340 --> 00:01:31,490 Talk about whatever you want in terms of material science 31 00:01:31,490 --> 00:01:34,420 and engineering, but make it entertaining, and make it 32 00:01:34,420 --> 00:01:37,650 engaging and accessible to freshmen. 33 00:01:37,650 --> 00:01:39,790 You should go to lectures. 34 00:01:39,790 --> 00:01:41,550 If you can't go to this one, then by all 35 00:01:41,550 --> 00:01:42,820 means, go to other seminars. 36 00:01:42,820 --> 00:01:46,150 If all you do when you come to MIT is go to class, you're 37 00:01:46,150 --> 00:01:48,240 missing out on some of the richness here. 38 00:01:48,240 --> 00:01:51,800 We have all sorts of people coming through here every day. 39 00:01:51,800 --> 00:01:54,210 And you can go to these seminars, you can learn a lot. 40 00:01:54,210 --> 00:01:56,600 You might say, well, I'm just a freshman, I'm not going to 41 00:01:56,600 --> 00:01:57,660 understand everything. 42 00:01:57,660 --> 00:01:58,490 I go to these things. 43 00:01:58,490 --> 00:02:00,070 I don't understand everything. 44 00:02:00,070 --> 00:02:02,300 But I learn something, because the first few minutes of the 45 00:02:02,300 --> 00:02:05,320 lecture, if the speaker is any good, he or she is going to 46 00:02:05,320 --> 00:02:07,650 set up the topic for you. 47 00:02:07,650 --> 00:02:09,850 If you follow the first five minutes, you'll have something 48 00:02:09,850 --> 00:02:13,630 that, you know, gets you oriented to the topic. 49 00:02:13,630 --> 00:02:16,040 And then the other thing, the other reason to go-- you see 50 00:02:16,040 --> 00:02:17,380 this on the poster-- 51 00:02:17,380 --> 00:02:20,960 room 10-250, reception immediately following. 52 00:02:20,960 --> 00:02:23,650 That means there will be refreshments! 53 00:02:23,650 --> 00:02:25,020 Food, for that, you know, 54 00:02:25,020 --> 00:02:26,700 pick-me-up in the late afternoon. 55 00:02:26,700 --> 00:02:29,330 So you go to the seminar, you know, sometimes they have 56 00:02:29,330 --> 00:02:32,810 refreshments before the speaker. 57 00:02:32,810 --> 00:02:35,830 I'm not going to tell you have to go into the seminar, having 58 00:02:35,830 --> 00:02:39,870 eaten the food and partaken of the refreshments. 59 00:02:39,870 --> 00:02:40,970 You didn't hear me say that. 60 00:02:40,970 --> 00:02:43,420 But anyways, there's always food around here. 61 00:02:43,420 --> 00:02:44,440 Go to this one. 62 00:02:44,440 --> 00:02:45,350 I think you'll enjoy it. 63 00:02:45,350 --> 00:02:47,610 And the speaker is Professor Michael Rubner. 64 00:02:47,610 --> 00:02:51,320 He's a faculty member in course 3. 65 00:02:51,320 --> 00:02:53,350 An excellent teacher. 66 00:02:53,350 --> 00:02:56,190 As you see, MacVicar Faculty Fellow, which means he's been 67 00:02:56,190 --> 00:02:57,680 acknowledged as a good teacher. 68 00:02:57,680 --> 00:02:59,340 I think you'll learn a lot. 69 00:02:59,340 --> 00:03:01,780 And he's talking about nature-inspired, so 70 00:03:01,780 --> 00:03:05,270 biomimetics, how we see things in nature and then mimic that 71 00:03:05,270 --> 00:03:08,520 design in advanced material science. 72 00:03:08,520 --> 00:03:08,990 OK. 73 00:03:08,990 --> 00:03:09,930 Enough said. 74 00:03:09,930 --> 00:03:11,300 Let's get on with the lesson. 75 00:03:11,300 --> 00:03:14,420 Last day we started looking at solutions, and we recognized 76 00:03:14,420 --> 00:03:17,450 that bonding is the key to understanding, and it's 77 00:03:17,450 --> 00:03:21,130 encapsulated in that catch-all phrase, like dissolves like. 78 00:03:21,130 --> 00:03:24,240 And towards the end, we talked about Ksp as a metric that 79 00:03:24,240 --> 00:03:26,780 helps us understand common ion effect. 80 00:03:26,780 --> 00:03:30,780 Common ion effect, again, if I tell you you have, say, 100 81 00:03:30,780 --> 00:03:34,785 units of sodium chloride that can go into solution, you 82 00:03:34,785 --> 00:03:36,610 would say, that's the solubility limit. 83 00:03:36,610 --> 00:03:38,960 But then if I tell you, I've got a solution that already 84 00:03:38,960 --> 00:03:42,540 contains 25 units of sodium chloride, that's a no-brainer. 85 00:03:42,540 --> 00:03:44,820 You've only got another 75 units to go. 86 00:03:44,820 --> 00:03:47,470 Now I say I've got potassium chloride in there. 87 00:03:47,470 --> 00:03:49,330 So now you stop and think, wait a minute. 88 00:03:49,330 --> 00:03:52,190 It's not sodium chloride, but it is a chloride. 89 00:03:52,190 --> 00:03:53,760 How do I think about this? 90 00:03:53,760 --> 00:03:57,660 Common ion effect through Ksp helps you reason through it. 91 00:03:57,660 --> 00:04:00,440 It's when you have more than one solute, and one of the 92 00:04:00,440 --> 00:04:03,550 constituents of the solute is already present. 93 00:04:03,550 --> 00:04:07,450 So today I want to talk about a subset of solutions, and in 94 00:04:07,450 --> 00:04:09,410 particular, I want to talk about acids and bases. 95 00:04:09,410 --> 00:04:12,230 And this is important, not only in materials processing, 96 00:04:12,230 --> 00:04:13,747 but we're going to have to understand this if we're going 97 00:04:13,747 --> 00:04:17,040 to go forward later and talk about biochemistry. 98 00:04:17,040 --> 00:04:19,100 So, you know, they're around us everywhere. 99 00:04:19,100 --> 00:04:21,060 You know, you probably got up this morning, you washed your 100 00:04:21,060 --> 00:04:23,980 hair with a pH-balanced shampoo, maybe had orange 101 00:04:23,980 --> 00:04:27,460 juice or grapefruit juice with citric and ascorbic acid. 102 00:04:27,460 --> 00:04:30,600 Your radio is powered by zinc alkaline batteries. 103 00:04:30,600 --> 00:04:34,400 I started my car, it's got the lead acid battery in it, and 104 00:04:34,400 --> 00:04:36,450 electricity for all my appliances came from 105 00:04:36,450 --> 00:04:39,020 coal-fired power plants, spewing out SO2, 106 00:04:39,020 --> 00:04:40,590 turning out acid rain. 107 00:04:40,590 --> 00:04:41,580 So we're off to a good start! 108 00:04:41,580 --> 00:04:43,260 It's Friday. 109 00:04:43,260 --> 00:04:45,000 So now we want to go back and understand 110 00:04:45,000 --> 00:04:46,230 this from the beginning. 111 00:04:46,230 --> 00:04:48,135 So we're going to start with a history lesson. 112 00:04:48,135 --> 00:04:51,520 And the history lesson starts in ancient times. 113 00:04:51,520 --> 00:04:56,350 Acids were known all the way back in early times for 114 00:04:56,350 --> 00:04:59,856 processing of food and materials. 115 00:04:59,856 --> 00:05:07,790 116 00:05:07,790 --> 00:05:10,530 So who among us hasn't eaten something 117 00:05:10,530 --> 00:05:11,600 that has been pickled? 118 00:05:11,600 --> 00:05:16,130 Pickle means to have been processed in acid solution. 119 00:05:16,130 --> 00:05:20,890 In fact, the word acid comes from the word acidus in Latin, 120 00:05:20,890 --> 00:05:24,265 and acidus means either sour or tart. 121 00:05:24,265 --> 00:05:27,330 122 00:05:27,330 --> 00:05:32,360 But the modern chemistry of acids and bases starts with 123 00:05:32,360 --> 00:05:38,475 Lavoisier in France in 1779. 124 00:05:38,475 --> 00:05:42,260 And I'm going to be naming many scientists from different 125 00:05:42,260 --> 00:05:44,180 countries today, so I'm going to use the 126 00:05:44,180 --> 00:05:45,800 international symbol. 127 00:05:45,800 --> 00:05:48,310 You know, these ovals that you put on the back of the car, so 128 00:05:48,310 --> 00:05:50,360 now if you see a car with this on it, you know 129 00:05:50,360 --> 00:05:51,970 it's a French registry. 130 00:05:51,970 --> 00:05:54,140 So he's probably got a Peugeot, and he's driving 131 00:05:54,140 --> 00:05:55,500 around with his Peugeot. 132 00:05:55,500 --> 00:05:59,640 And what Lavoisier said, in trying to understand acids and 133 00:05:59,640 --> 00:06:00,680 bases, is-- 134 00:06:00,680 --> 00:06:03,290 it's a really interesting story. 135 00:06:03,290 --> 00:06:06,997 He said that oxygen is present in all acids. 136 00:06:06,997 --> 00:06:17,650 137 00:06:17,650 --> 00:06:18,780 And why? 138 00:06:18,780 --> 00:06:21,500 Because he spent most of his career studying combustion, so 139 00:06:21,500 --> 00:06:24,510 he was very concerned about oxygen. 140 00:06:24,510 --> 00:06:30,240 And the interesting thing is that oxygen, the name of the 141 00:06:30,240 --> 00:06:34,920 gas, oxygen, actually comes from the greek oxy, which 142 00:06:34,920 --> 00:06:39,380 means sharp, and, you know, the particle gen, as in to 143 00:06:39,380 --> 00:06:41,290 generate or to be born. 144 00:06:41,290 --> 00:06:42,540 OK? 145 00:06:42,540 --> 00:06:44,120 146 00:06:44,120 --> 00:06:49,540 So it's interesting that this gas is named incorrectly. 147 00:06:49,540 --> 00:06:55,110 It's named for an attribute that is ascribed to acid, and 148 00:06:55,110 --> 00:06:57,210 it's wrong. 149 00:06:57,210 --> 00:06:58,710 And it's in other languages, too. 150 00:06:58,710 --> 00:07:01,890 The word oxygen translates into other languages as 151 00:07:01,890 --> 00:07:04,340 meaning something sharp, and it has nothing to do with it. 152 00:07:04,340 --> 00:07:07,500 But while we're on the topic of Lavoisier, Lavoisier did 153 00:07:07,500 --> 00:07:10,030 study oxygen. 154 00:07:10,030 --> 00:07:15,620 And there was an intense rivalry between Lavoisier in 155 00:07:15,620 --> 00:07:21,950 France, Joseph Priestley in Britain, 156 00:07:21,950 --> 00:07:26,000 and Scheele in Sweden. 157 00:07:26,000 --> 00:07:29,460 And all three of them were working simultaneously to 158 00:07:29,460 --> 00:07:33,680 study combustion and understand oxygen. 159 00:07:33,680 --> 00:07:35,970 And here I've got a very nice image. 160 00:07:35,970 --> 00:07:40,290 This is a portrait of Lavoisier with his wife. 161 00:07:40,290 --> 00:07:42,440 And it's hard to see. 162 00:07:42,440 --> 00:07:45,460 If the lights were a little bit dimmer, you'd see-- 163 00:07:45,460 --> 00:07:48,540 notice here, you see all of this chemical apparatus. 164 00:07:48,540 --> 00:07:53,400 There is bell jars, and various glass apparatus. 165 00:07:53,400 --> 00:07:57,270 His wife was his partner in the laboratory. 166 00:07:57,270 --> 00:07:59,350 She was unique among French women in 167 00:07:59,350 --> 00:08:01,920 that she read English. 168 00:08:01,920 --> 00:08:05,600 And in his rivalry with Priestley, he relied on his 169 00:08:05,600 --> 00:08:08,660 wife in order to read Priestley's writings. 170 00:08:08,660 --> 00:08:09,530 So they worked together. 171 00:08:09,530 --> 00:08:12,960 She even helped him in the laboratory. 172 00:08:12,960 --> 00:08:17,020 They married at the time he was 27 and she was 13, and 173 00:08:17,020 --> 00:08:17,720 they were-- 174 00:08:17,720 --> 00:08:18,960 what are you so shocked about? 175 00:08:18,960 --> 00:08:23,650 It's France, and it's 1779! 176 00:08:23,650 --> 00:08:24,580 Get over it! 177 00:08:24,580 --> 00:08:28,720 Anyways, she helped him a lot, and we'll say a little bit 178 00:08:28,720 --> 00:08:32,590 more about that later. 179 00:08:32,590 --> 00:08:32,930 OK. 180 00:08:32,930 --> 00:08:36,370 So now let's go on to the next part of the history lesson. 181 00:08:36,370 --> 00:08:39,740 So so far, we've got one explanation, and it's wrong. 182 00:08:39,740 --> 00:08:42,340 So let's go to the next one, and we'll go to Britain. 183 00:08:42,340 --> 00:08:47,230 Sir Humphry Davy in London in 1810. 184 00:08:47,230 --> 00:08:50,240 So we'll put GB here, and he's driving around in his little 185 00:08:50,240 --> 00:08:51,740 Jaguar, I suspect. 186 00:08:51,740 --> 00:08:53,560 And he said something that was correct. 187 00:08:53,560 --> 00:08:57,000 He said that it's hydrogen present in all acids. 188 00:08:57,000 --> 00:09:02,760 189 00:09:02,760 --> 00:09:03,750 And that was pretty much it. 190 00:09:03,750 --> 00:09:06,290 He was a great scientist, did some very good work, but 191 00:09:06,290 --> 00:09:08,450 really didn't do anything quantitative here. 192 00:09:08,450 --> 00:09:11,600 So for the quantitative stuff, we have to wait for almost the 193 00:09:11,600 --> 00:09:12,980 end of the century. 194 00:09:12,980 --> 00:09:15,240 And we go up to Sweden again, to Arrhenius. 195 00:09:15,240 --> 00:09:19,590 And Arrhenius, in 1887-- 196 00:09:19,590 --> 00:09:21,300 so I'll give him a Volvo. 197 00:09:21,300 --> 00:09:26,750 And he said that the acid is a substance that disassociates 198 00:09:26,750 --> 00:09:28,740 to produce protons. 199 00:09:28,740 --> 00:09:37,940 So the acid is defined as a solution that dissociates to 200 00:09:37,940 --> 00:09:40,410 give protons. 201 00:09:40,410 --> 00:09:44,540 I'm going to say H plus, meaning the hydrogen ion, or P 202 00:09:44,540 --> 00:09:47,770 plus, and we're going to keep using the term proton. 203 00:09:47,770 --> 00:09:50,560 I'm not going to say hydrogen ion, I'm going to say proton. 204 00:09:50,560 --> 00:09:51,890 So proton in solution. 205 00:09:51,890 --> 00:09:53,370 So this is what he defines. 206 00:09:53,370 --> 00:09:55,270 And he further defines the base. 207 00:09:55,270 --> 00:09:58,800 He defines the base as the complement to the acid. 208 00:09:58,800 --> 00:10:02,420 And he says that the base is something that dissociates to 209 00:10:02,420 --> 00:10:04,360 give us hydroxyl. 210 00:10:04,360 --> 00:10:12,380 The base dissociates to give OH minus the hydroxyl. 211 00:10:12,380 --> 00:10:17,220 And so now we've got this whole concept of electrolytic 212 00:10:17,220 --> 00:10:21,530 disassociation, which is what wins him the Nobel prize in 213 00:10:21,530 --> 00:10:23,690 1903 for this thing. 214 00:10:23,690 --> 00:10:27,800 And then we saw last day how the addition of ions to water 215 00:10:27,800 --> 00:10:29,050 gives charge carriers. 216 00:10:29,050 --> 00:10:33,350 And so the presence of protons and hydroxyl is, in fact, the 217 00:10:33,350 --> 00:10:37,350 way we have any charge carried through water. 218 00:10:37,350 --> 00:10:40,450 So up until now, when I said electrical conductivity, we 219 00:10:40,450 --> 00:10:43,830 were pretty much referring to electronic conductivity. 220 00:10:43,830 --> 00:10:46,740 But there's a second kind of conductivity, and we can have 221 00:10:46,740 --> 00:10:49,500 ionic conductivity. 222 00:10:49,500 --> 00:10:52,900 Ionic conductivity, as the name implies, is not by 223 00:10:52,900 --> 00:10:54,730 electrons, but by ions. 224 00:10:54,730 --> 00:10:56,915 And this is typically ions in solution. 225 00:10:56,915 --> 00:11:00,190 226 00:11:00,190 --> 00:11:03,820 Ionic conductivity in solution, and a solution that 227 00:11:03,820 --> 00:11:06,165 is an ionic conductor is called an electrolyte. 228 00:11:06,165 --> 00:11:08,910 229 00:11:08,910 --> 00:11:10,740 So we have electrolyte in our bodies, 230 00:11:10,740 --> 00:11:14,290 saline, about 5% chloride. 231 00:11:14,290 --> 00:11:16,730 We have electrolyte in batteries that are ionically 232 00:11:16,730 --> 00:11:17,930 conductive. 233 00:11:17,930 --> 00:11:23,160 And the term simply means, we have conduction by ions. 234 00:11:23,160 --> 00:11:27,390 And so it was the theory of electrolytic dissociation that 235 00:11:27,390 --> 00:11:30,030 won the Nobel prize. 236 00:11:30,030 --> 00:11:32,260 So how does this work? 237 00:11:32,260 --> 00:11:36,230 So we can start with something like HCl gas. 238 00:11:36,230 --> 00:11:39,540 I'm going to dissolve it in water, and this will give me 239 00:11:39,540 --> 00:11:41,155 proton, H plus. 240 00:11:41,155 --> 00:11:44,940 And I'm going to write aq, meaning that it's dissolved in 241 00:11:44,940 --> 00:11:50,120 water, and the chloride ion, also dissolved in water. 242 00:11:50,120 --> 00:11:52,920 And so this gives me an acid. 243 00:11:52,920 --> 00:11:55,130 This is a proton donor. 244 00:11:55,130 --> 00:11:56,030 And now let's look at 245 00:11:56,030 --> 00:11:58,380 something like sodium hydroxide. 246 00:11:58,380 --> 00:12:00,800 Sodium hydroxide at room temperature is an ionic 247 00:12:00,800 --> 00:12:05,440 compound, so it is a solid, but it is soluble in a polar, 248 00:12:05,440 --> 00:12:13,420 hydrogen-bonded liquid, so H20, to give hydroxyl aqueous 249 00:12:13,420 --> 00:12:16,700 plus sodium ion aqueous. 250 00:12:16,700 --> 00:12:19,270 So again, we see the dissociation. 251 00:12:19,270 --> 00:12:21,800 And then we can have, from here, a 252 00:12:21,800 --> 00:12:24,240 neutralization reaction. 253 00:12:24,240 --> 00:12:26,740 And the neutralization reaction is simply 254 00:12:26,740 --> 00:12:29,520 reconstitution of the solvent. 255 00:12:29,520 --> 00:12:33,870 So neutralization, another way to think about it, because 256 00:12:33,870 --> 00:12:36,300 we're not going to be confined to water by the end of the 257 00:12:36,300 --> 00:12:40,340 lecture, neutralization is simply a reaction that results 258 00:12:40,340 --> 00:12:44,230 in reconstitution of the solvents. 259 00:12:44,230 --> 00:12:46,330 So the solvent, in this case, is water. 260 00:12:46,330 --> 00:12:48,260 So how would we reconstitute water? 261 00:12:48,260 --> 00:12:50,520 We combine proton with hydroxyl. 262 00:12:50,520 --> 00:12:55,110 So let's do that and see the result of that reaction. 263 00:12:55,110 --> 00:13:00,360 So if I take, and run it in the vertical direction, proton 264 00:13:00,360 --> 00:13:05,130 plus hydroxyl, we'll give water again-- 265 00:13:05,130 --> 00:13:07,580 let's give H20 liquid-- 266 00:13:07,580 --> 00:13:11,080 and now you can see Na plus Cl will give me 267 00:13:11,080 --> 00:13:14,310 NaCl, aqueous dissolved. 268 00:13:14,310 --> 00:13:16,590 So this is what you probably learned in your high school 269 00:13:16,590 --> 00:13:21,230 chemistry, that acid plus base ca give you salt plus water. 270 00:13:21,230 --> 00:13:24,910 So you see all of this resulting from just the simple 271 00:13:24,910 --> 00:13:26,640 Arrhenius definition. 272 00:13:26,640 --> 00:13:27,580 So this is good. 273 00:13:27,580 --> 00:13:30,800 We've got off to a decent start here with Arrhenius. 274 00:13:30,800 --> 00:13:34,470 But then the theory has its limitations, as they all do. 275 00:13:34,470 --> 00:13:36,420 And how do we discover the limitations? 276 00:13:36,420 --> 00:13:37,860 With some new data. 277 00:13:37,860 --> 00:13:39,460 So let's look at some data. 278 00:13:39,460 --> 00:13:45,950 So it had been known for a long time that ammonia, when 279 00:13:45,950 --> 00:13:50,950 it's dissolved in water, can act as a solution capable of 280 00:13:50,950 --> 00:13:52,840 neutralizing an acid. 281 00:13:52,840 --> 00:13:55,780 So if ammonia dissolved in water neutralizes an acid, 282 00:13:55,780 --> 00:13:56,845 then this must be a base. 283 00:13:56,845 --> 00:13:59,290 But look, there's no hydroxyl here. 284 00:13:59,290 --> 00:14:01,910 So the Arrhenius definition of base is inadequate 285 00:14:01,910 --> 00:14:03,630 to account for this. 286 00:14:03,630 --> 00:14:04,910 So let's just get that down. 287 00:14:04,910 --> 00:14:08,750 Ammonia, which you know is a gas at room temperature, will 288 00:14:08,750 --> 00:14:15,520 neutralize acids. 289 00:14:15,520 --> 00:14:20,020 But no hydroxyl present. 290 00:14:20,020 --> 00:14:24,980 So something's going on here that we can't account for by 291 00:14:24,980 --> 00:14:26,950 the simple Arrhenius definition. 292 00:14:26,950 --> 00:14:30,020 So to get us out of this conundrum, we had to wait 293 00:14:30,020 --> 00:14:31,410 until 1923. 294 00:14:31,410 --> 00:14:34,620 And two scientists simultaneously enunciated the 295 00:14:34,620 --> 00:14:35,560 same ideas. 296 00:14:35,560 --> 00:14:37,640 So I'm going to put them both down. 297 00:14:37,640 --> 00:14:38,680 1923. 298 00:14:38,680 --> 00:14:44,850 Bronsted, who was in Denmark, and Lowry, who was 299 00:14:44,850 --> 00:14:46,800 working in the UK. 300 00:14:46,800 --> 00:14:50,830 Also 1923. 301 00:14:50,830 --> 00:14:53,380 And I'll give him a Jaguar as well. 302 00:14:53,380 --> 00:14:56,540 And so the two of them proposed a broader definition 303 00:14:56,540 --> 00:14:58,790 to account for what's going on here. 304 00:14:58,790 --> 00:14:59,710 And what did they say? 305 00:14:59,710 --> 00:15:01,640 They said that acid-- 306 00:15:01,640 --> 00:15:04,630 they'll keep the same definition as Arrhenius. 307 00:15:04,630 --> 00:15:07,280 So an acid is going to be a proton donor. 308 00:15:07,280 --> 00:15:10,240 309 00:15:10,240 --> 00:15:11,300 So that's good. 310 00:15:11,300 --> 00:15:14,780 Let's even put here, same as Arrhenius. 311 00:15:14,780 --> 00:15:18,150 312 00:15:18,150 --> 00:15:19,830 But now here's the difference. 313 00:15:19,830 --> 00:15:24,500 The base is no longer confined to hydroxyl chemistry. 314 00:15:24,500 --> 00:15:26,710 They call it a proton acceptor. 315 00:15:26,710 --> 00:15:30,140 316 00:15:30,140 --> 00:15:31,970 And that's different. 317 00:15:31,970 --> 00:15:35,530 So hydroxyl-free. 318 00:15:35,530 --> 00:15:37,470 Now, let's be careful here. 319 00:15:37,470 --> 00:15:39,630 If I propose this new definition, I 320 00:15:39,630 --> 00:15:40,970 can't throw out hydroxyl. 321 00:15:40,970 --> 00:15:43,990 So you've got to watch to make sure that by broadening the 322 00:15:43,990 --> 00:15:46,030 definition, we don't exclude hydroxyl. 323 00:15:46,030 --> 00:15:49,650 So the theory has to encompass what we already know, and then 324 00:15:49,650 --> 00:15:53,350 continue to encompass things that tend to contradict what 325 00:15:53,350 --> 00:15:54,060 we already know. 326 00:15:54,060 --> 00:15:56,540 So let's take a look at what this gives us. 327 00:15:56,540 --> 00:16:01,750 So I'm going to write a broader equation here. 328 00:16:01,750 --> 00:16:06,180 I'm going to write this as the acid. 329 00:16:06,180 --> 00:16:07,290 So what do I have? 330 00:16:07,290 --> 00:16:10,180 I have every acid has to have a proton in 331 00:16:10,180 --> 00:16:12,100 it, plus some residual. 332 00:16:12,100 --> 00:16:15,380 So I can rewrite the acid in this form. 333 00:16:15,380 --> 00:16:18,990 I'm going to react it with a base. 334 00:16:18,990 --> 00:16:21,300 So according to this definition, this has to be a 335 00:16:21,300 --> 00:16:23,170 proton donor. 336 00:16:23,170 --> 00:16:25,060 And this, you're going to watch me on this one. 337 00:16:25,060 --> 00:16:27,390 This is going to be a proton acceptor. 338 00:16:27,390 --> 00:16:28,690 And we'll put some identities here. 339 00:16:28,690 --> 00:16:30,520 Eventually we're going to write this with ammonia in it, 340 00:16:30,520 --> 00:16:32,850 but let's just do the broad definition. 341 00:16:32,850 --> 00:16:36,200 So what happens is, if this is a proton acceptor, on this 342 00:16:36,200 --> 00:16:38,820 side of the equation, it takes the proton from here. 343 00:16:38,820 --> 00:16:40,010 This is the proton donor. 344 00:16:40,010 --> 00:16:45,130 It gives it away, and we end up with a BH plus. 345 00:16:45,130 --> 00:16:48,400 So this proton acceptor has accepted the proton, leaving 346 00:16:48,400 --> 00:16:52,660 behind the deprotonated A minus. 347 00:16:52,660 --> 00:16:54,260 That's a nice little reaction. 348 00:16:54,260 --> 00:16:57,850 But now, if you'd nodded off for the last 90 seconds, and 349 00:16:57,850 --> 00:17:01,010 then opened your eyes and said, well, he said acid is a 350 00:17:01,010 --> 00:17:04,460 proton donor, this thing can give up a proton. 351 00:17:04,460 --> 00:17:08,090 So OK, I'm going to call this thing a proton donor. 352 00:17:08,090 --> 00:17:10,410 And this is most certainly a proton acceptor. 353 00:17:10,410 --> 00:17:12,660 Look, it has accepted the proton. 354 00:17:12,660 --> 00:17:16,890 So this is going to be a proton acceptor. 355 00:17:16,890 --> 00:17:20,050 So now I've got in this equation two proton donors and 356 00:17:20,050 --> 00:17:21,910 two proton acceptors. 357 00:17:21,910 --> 00:17:23,160 And they're linked. 358 00:17:23,160 --> 00:17:26,660 This proton donor, BH plus, is linked to B. 359 00:17:26,660 --> 00:17:30,360 So I'm going to put a little yolk over this one. 360 00:17:30,360 --> 00:17:34,200 And this HA, the original acid, is linked to 361 00:17:34,200 --> 00:17:36,630 this base, A minus. 362 00:17:36,630 --> 00:17:38,425 So I'm going to put a yoke over that. 363 00:17:38,425 --> 00:17:41,430 364 00:17:41,430 --> 00:17:47,730 And the Latin word for yoke, to yoke, is jugere, from which 365 00:17:47,730 --> 00:17:50,350 we get the word conjugate. 366 00:17:50,350 --> 00:17:52,560 So I'm going to call these things 367 00:17:52,560 --> 00:17:54,665 conjugate acid-base pairs. 368 00:17:54,665 --> 00:18:02,050 369 00:18:02,050 --> 00:18:04,770 And every equation has two. 370 00:18:04,770 --> 00:18:06,840 Because you've got a proton donor proton acceptor. 371 00:18:06,840 --> 00:18:09,130 So now this is, follow the bouncing ball. 372 00:18:09,130 --> 00:18:11,880 If you want to understand acid-base chemistry, just 373 00:18:11,880 --> 00:18:12,950 follow the proton. 374 00:18:12,950 --> 00:18:15,100 Here's proton here, goes over here. 375 00:18:15,100 --> 00:18:18,980 Here's something deprotonated, now it's protonated. 376 00:18:18,980 --> 00:18:22,130 That's the rhythm here. 377 00:18:22,130 --> 00:18:27,250 So the whole thing is, acid-base reactions can be 378 00:18:27,250 --> 00:18:29,965 defined as a proton transfer reactions. 379 00:18:29,965 --> 00:18:33,500 380 00:18:33,500 --> 00:18:37,590 Remember we talked about ionicity and electron transfer 381 00:18:37,590 --> 00:18:40,090 in order to achieve octet stability? 382 00:18:40,090 --> 00:18:42,140 So we saw the whole life and times of 383 00:18:42,140 --> 00:18:43,600 electron transfer reactions. 384 00:18:43,600 --> 00:18:47,470 Now life and times of proton transfer reactions. 385 00:18:47,470 --> 00:18:47,840 OK. 386 00:18:47,840 --> 00:18:50,710 And last thing I want to do, is to just make sure that we 387 00:18:50,710 --> 00:18:52,360 see the definitions. 388 00:18:52,360 --> 00:18:55,870 You know, all queens are female, but not all females 389 00:18:55,870 --> 00:18:56,950 are queens. 390 00:18:56,950 --> 00:18:59,200 So this one here, what's this? 391 00:18:59,200 --> 00:19:01,840 This is definitely, it's a proton donor. 392 00:19:01,840 --> 00:19:02,990 So it's an acid. 393 00:19:02,990 --> 00:19:06,350 So it's definitely an Arrhenius acid, because it's 394 00:19:06,350 --> 00:19:11,850 got a proton, and it's also a Bronsted-Lowry acid. 395 00:19:11,850 --> 00:19:14,270 Now, what about this one? 396 00:19:14,270 --> 00:19:15,510 This is a base. 397 00:19:15,510 --> 00:19:17,690 It may not have hydroxyl in it. 398 00:19:17,690 --> 00:19:18,670 May or may not. 399 00:19:18,670 --> 00:19:22,580 So this is definitely a Bronsted-Lowry base, but I 400 00:19:22,580 --> 00:19:25,730 can't say for sure that it's an Arrhenius base, because 401 00:19:25,730 --> 00:19:28,100 Arrhenius has to be O minus. 402 00:19:28,100 --> 00:19:29,460 This one here, what about this? 403 00:19:29,460 --> 00:19:33,310 Unless it's OH minus, this one here is, what? 404 00:19:33,310 --> 00:19:36,950 It's Bronsted-Lowry base. 405 00:19:36,950 --> 00:19:41,010 And this one here, this can be both Bronsted-Lowry acid and 406 00:19:41,010 --> 00:19:44,070 it can be an Arrhenius acid. 407 00:19:44,070 --> 00:19:47,940 So this is how we can differentiate them. 408 00:19:47,940 --> 00:19:50,400 OK, good. 409 00:19:50,400 --> 00:19:53,920 Now let's go to the ammonia, see if we've got ourselves out 410 00:19:53,920 --> 00:19:57,330 of the conundrum so we can write now NH3. 411 00:19:57,330 --> 00:19:58,920 And I'm going to say that this is ammonia 412 00:19:58,920 --> 00:20:00,320 that's already dissolved. 413 00:20:00,320 --> 00:20:04,020 So ammonia is already in aqueous solution, and it 414 00:20:04,020 --> 00:20:10,170 reacts with water, H20 liquid, to do what? 415 00:20:10,170 --> 00:20:12,250 This is supposed to be a-- 416 00:20:12,250 --> 00:20:16,390 if this is a base, remember, this is the thing that we're 417 00:20:16,390 --> 00:20:17,390 trying to demonstrate. 418 00:20:17,390 --> 00:20:20,180 If it's a base, according to this, it's a proton acceptor. 419 00:20:20,180 --> 00:20:22,920 So I'm going to stick a proton on this, and I'm going to get 420 00:20:22,920 --> 00:20:26,450 NH4 plus the ammonium ion. 421 00:20:26,450 --> 00:20:29,010 422 00:20:29,010 --> 00:20:30,940 And how did I get the ammonium ion? 423 00:20:30,940 --> 00:20:36,950 I took a proton from water, leaving behind OH. 424 00:20:36,950 --> 00:20:39,480 So can you see that how this thing works? 425 00:20:39,480 --> 00:20:43,430 By gobbling up protons, by becoming a proton vacuum 426 00:20:43,430 --> 00:20:48,020 cleaner, it takes protons out of water, leaving 427 00:20:48,020 --> 00:20:49,630 an excess of hydroxyl. 428 00:20:49,630 --> 00:20:52,710 And in effect, now we've got something that's tantamount to 429 00:20:52,710 --> 00:20:54,030 an Arrhenius base. 430 00:20:54,030 --> 00:20:55,930 But it all started off with this. 431 00:20:55,930 --> 00:20:57,760 So now we can link these two. 432 00:20:57,760 --> 00:21:02,300 I'm going to yoke ammonium and ammonia as conjugate 433 00:21:02,300 --> 00:21:05,280 acid-base, and there is water and hydroxyl 434 00:21:05,280 --> 00:21:06,850 as acid-base pairs. 435 00:21:06,850 --> 00:21:10,770 So again, let's get the colors going. 436 00:21:10,770 --> 00:21:12,460 Here we've got Bronsted-Lowry-- 437 00:21:12,460 --> 00:21:14,380 the bases are always going to be in blue. 438 00:21:14,380 --> 00:21:16,340 Blue and base both begin with the letter B. 439 00:21:16,340 --> 00:21:19,950 So this is definitely Brosted-Lowry base, but it's 440 00:21:19,950 --> 00:21:22,110 not an Arrhenius base. 441 00:21:22,110 --> 00:21:26,100 This is a Bronsted-Lowry base, and it's also 442 00:21:26,100 --> 00:21:28,570 an Arrhenius base. 443 00:21:28,570 --> 00:21:31,160 This one here, we can call this one-- 444 00:21:31,160 --> 00:21:35,000 in this case, it's a proton donor, so it's both an 445 00:21:35,000 --> 00:21:37,880 Arrhenius acid and a Bronsted-Lowry acid. 446 00:21:37,880 --> 00:21:38,760 But look at this. 447 00:21:38,760 --> 00:21:41,740 You'd say, OK, I know what he's doing. 448 00:21:41,740 --> 00:21:44,760 Arrheius, Bronsted-Lowry, Arrhenius, Bronsted-Lowry. 449 00:21:44,760 --> 00:21:47,170 This is Bronsted-Lowry only, this must be 450 00:21:47,170 --> 00:21:48,420 Bronsted-Lowry only. 451 00:21:48,420 --> 00:21:49,070 But look! 452 00:21:49,070 --> 00:21:51,540 This is a proton donor. 453 00:21:51,540 --> 00:21:53,100 It dissociates to give protons. 454 00:21:53,100 --> 00:21:57,420 So this is both Bronsted-Lowry and Arrhenius. 455 00:21:57,420 --> 00:21:59,640 Most people will miss that. 456 00:21:59,640 --> 00:22:03,410 We'll get to see, maybe, on a subsequent celebration, how 457 00:22:03,410 --> 00:22:05,370 many of you miss that. 458 00:22:05,370 --> 00:22:05,680 OK. 459 00:22:05,680 --> 00:22:06,330 So. 460 00:22:06,330 --> 00:22:08,570 So now, let's go into the chemistry here. 461 00:22:08,570 --> 00:22:11,730 Because I said up here at the beginning of the lecture-- 462 00:22:11,730 --> 00:22:14,740 what is it-- bonding is the key to understanding. 463 00:22:14,740 --> 00:22:18,030 So what is it about bonding here that defines the 464 00:22:18,030 --> 00:22:19,310 Bronsted-Lowry base? 465 00:22:19,310 --> 00:22:23,240 So I'm going to write this reaction in this way, now. 466 00:22:23,240 --> 00:22:25,810 I'm going to put-- here's the proton, which 467 00:22:25,810 --> 00:22:27,220 is coming from water. 468 00:22:27,220 --> 00:22:29,290 And I'm going to write that with NH3. 469 00:22:29,290 --> 00:22:31,610 I'm going to use the Lewis structure. 470 00:22:31,610 --> 00:22:35,730 So, you know, Lewis structure looks like this, Nitrate has 471 00:22:35,730 --> 00:22:39,380 got five valence electrons, three of them are bound, and 472 00:22:39,380 --> 00:22:41,010 now I've got this long pair. 473 00:22:41,010 --> 00:22:45,580 So what do we know about the electronic 474 00:22:45,580 --> 00:22:46,960 structure of proton? 475 00:22:46,960 --> 00:22:47,770 What does it look like? 476 00:22:47,770 --> 00:22:49,020 What's the Lewis structure of proton? 477 00:22:49,020 --> 00:22:52,080 478 00:22:52,080 --> 00:22:54,480 How many electrons on proton? 479 00:22:54,480 --> 00:22:54,900 None. 480 00:22:54,900 --> 00:22:56,680 This is nothing. 481 00:22:56,680 --> 00:22:59,520 This is very needy. 482 00:22:59,520 --> 00:23:02,910 It's like the neediest friend you have. You know, the one 483 00:23:02,910 --> 00:23:05,530 that's always taking stuff from you, taking your 484 00:23:05,530 --> 00:23:08,950 emotional energy, giving back nothing? 485 00:23:08,950 --> 00:23:10,180 That's proton. 486 00:23:10,180 --> 00:23:12,100 That's the human equivalent of proton. 487 00:23:12,100 --> 00:23:17,310 So if proton wants to make a bond to form NH4, proton is 488 00:23:17,310 --> 00:23:22,590 going to come over here and exploit both electrons. 489 00:23:22,590 --> 00:23:26,700 So if this is going to be a proton acceptor, the only way 490 00:23:26,700 --> 00:23:30,000 it can be a proton acceptor is to have two 491 00:23:30,000 --> 00:23:32,130 unused electrons available. 492 00:23:32,130 --> 00:23:34,520 This is going to be a dative bond, agreed? 493 00:23:34,520 --> 00:23:37,450 Dative, because both electrons from the bond 494 00:23:37,450 --> 00:23:38,780 come from the nitrogen. 495 00:23:38,780 --> 00:23:41,510 The proton doesn't contribute anything. 496 00:23:41,510 --> 00:23:43,060 So that's the hallmark. 497 00:23:43,060 --> 00:23:49,900 The proton acceptor axiomatically must have an 498 00:23:49,900 --> 00:23:53,480 available non-bonding pair. 499 00:23:53,480 --> 00:23:59,660 So wherever you see non-bonding pairs, wherever 500 00:23:59,660 --> 00:24:03,010 you see a compound that has this capability, it could 501 00:24:03,010 --> 00:24:07,870 serve as a Bronsted-Lowry base. 502 00:24:07,870 --> 00:24:12,140 We know that water, because it has hydroxyl in it, has to 503 00:24:12,140 --> 00:24:12,910 satisfy this. 504 00:24:12,910 --> 00:24:13,970 So let's take a look. 505 00:24:13,970 --> 00:24:16,940 H20 we can do similarly. 506 00:24:16,940 --> 00:24:18,190 Oxygen. 507 00:24:18,190 --> 00:24:21,050 It's got 6 electrons, 2 are in the, bonds and we have 2 508 00:24:21,050 --> 00:24:22,520 non-bonding pairs. 509 00:24:22,520 --> 00:24:26,380 So then when we attach proton here, we make 510 00:24:26,380 --> 00:24:29,050 something called hydronium. 511 00:24:29,050 --> 00:24:32,390 We make hydronium ion. 512 00:24:32,390 --> 00:24:34,750 So it's a little fancier than just saying, I've got this 513 00:24:34,750 --> 00:24:37,960 naked proton with no electrons swimming around in water. 514 00:24:37,960 --> 00:24:41,340 In fact, it's more coordinated like this. 515 00:24:41,340 --> 00:24:44,180 H30 plus, and while we're in the neighborhood, we 516 00:24:44,180 --> 00:24:44,870 might as well show. 517 00:24:44,870 --> 00:24:46,930 This is sp3 hybridized. 518 00:24:46,930 --> 00:24:51,190 We've got one, two, three, four orbitals. 519 00:24:51,190 --> 00:24:52,560 Hydrogen's on three. 520 00:24:52,560 --> 00:24:56,180 It's got a net charge of plus 1, and lone pair 521 00:24:56,180 --> 00:24:57,620 on the fourth side. 522 00:24:57,620 --> 00:25:01,680 So there's the structure of hydronium. 523 00:25:01,680 --> 00:25:04,310 And we can now write the equation. 524 00:25:04,310 --> 00:25:14,050 We can say H20 liquid plus H20 liquid gives me H3O 525 00:25:14,050 --> 00:25:18,520 plus, plus OH minus. 526 00:25:18,520 --> 00:25:22,520 So this is now the self-ionization or 527 00:25:22,520 --> 00:25:23,720 self-dissociation reaction. 528 00:25:23,720 --> 00:25:26,520 So now I can pair these as well. 529 00:25:26,520 --> 00:25:28,540 I can yoke these. 530 00:25:28,540 --> 00:25:29,890 I have acid-base pair. 531 00:25:29,890 --> 00:25:36,100 So this is acid here, and the conjugate base is water, H20. 532 00:25:36,100 --> 00:25:39,180 Hydroxyl, we know, has to be a base, and its 533 00:25:39,180 --> 00:25:41,720 conjugate acid is water. 534 00:25:41,720 --> 00:25:44,100 So you see, in the same equation, same place, same 535 00:25:44,100 --> 00:25:48,340 time, water is acting as both acid and base relative to 536 00:25:48,340 --> 00:25:50,440 these two species. 537 00:25:50,440 --> 00:25:55,080 And so we call such a such a compound that acts as both 538 00:25:55,080 --> 00:25:57,360 acid and base, we call it amphipathic. 539 00:25:57,360 --> 00:26:01,930 540 00:26:01,930 --> 00:26:04,310 Has two moods. 541 00:26:04,310 --> 00:26:06,082 You know, amphi, like in amphitheater. 542 00:26:06,082 --> 00:26:07,870 Have you ever seen a Roman theater? 543 00:26:07,870 --> 00:26:09,575 It looks like this from the top down. 544 00:26:09,575 --> 00:26:12,410 It's got all this, you know, like this, and all the people 545 00:26:12,410 --> 00:26:14,690 are here, and there's the stage up here. 546 00:26:14,690 --> 00:26:22,440 But if I make a theater in the round, that is amphitheater. 547 00:26:22,440 --> 00:26:26,120 Or as it's commonly mispronounced, ampitheater. 548 00:26:26,120 --> 00:26:28,750 3091ers do not say ampitheater, they say 549 00:26:28,750 --> 00:26:29,810 amphitheater. 550 00:26:29,810 --> 00:26:33,130 So this reaction here is self-dissociation. 551 00:26:33,130 --> 00:26:33,400 Right? 552 00:26:33,400 --> 00:26:38,300 This reaction is self-dissociation of water. 553 00:26:38,300 --> 00:26:41,980 Or because we're forming ions, it's also called 554 00:26:41,980 --> 00:26:43,230 self-ionization. 555 00:26:43,230 --> 00:26:48,260 556 00:26:48,260 --> 00:26:51,110 Self-dissociation or self-ionization of water. 557 00:26:51,110 --> 00:26:55,710 Now, turns out that the chemical's power of H3O plus 558 00:26:55,710 --> 00:26:57,620 and OH minus is very high. 559 00:26:57,620 --> 00:27:00,350 So this reaction doesn't go very far to the right. 560 00:27:00,350 --> 00:27:04,690 The amount of the dissociation is tiny, and to be specific, 561 00:27:04,690 --> 00:27:09,790 at 25 degrees C, the amount of, if you take deionized, 562 00:27:09,790 --> 00:27:13,530 deaerated water, absolutely pure and pristine. 563 00:27:13,530 --> 00:27:18,120 The amount of native H30 plus and OH minus is on the order 564 00:27:18,120 --> 00:27:21,020 of one part in 10 million. 565 00:27:21,020 --> 00:27:24,520 So H3O plus concentration would be 10 566 00:27:24,520 --> 00:27:26,910 to the minus 7 molar. 567 00:27:26,910 --> 00:27:29,810 And obviously, from the stoichiometry of the equation, 568 00:27:29,810 --> 00:27:34,910 you get the identical amount of OH minus. 569 00:27:34,910 --> 00:27:37,740 Well, that's in the self-dissociation. 570 00:27:37,740 --> 00:27:41,490 And so you have very, very few charge carriers, which is why 571 00:27:41,490 --> 00:27:46,090 high-purity water is a very poor conductor of electricity, 572 00:27:46,090 --> 00:27:48,140 even as an electrolyte. 573 00:27:48,140 --> 00:27:50,550 And that's, I've told you in the past, that could be one 574 00:27:50,550 --> 00:27:52,390 indicator of certain toxins. 575 00:27:52,390 --> 00:27:54,550 If you measure the conductivity of water and you 576 00:27:54,550 --> 00:27:57,390 discover it's abnormally high, and it's putatively supposed 577 00:27:57,390 --> 00:28:00,460 to be pure water, that's an indication that 578 00:28:00,460 --> 00:28:01,320 it's not pure water. 579 00:28:01,320 --> 00:28:03,380 There's some other charge carriers present. 580 00:28:03,380 --> 00:28:09,880 So we can write a Ksp we analogy. 581 00:28:09,880 --> 00:28:13,200 And it's called the water ionization constant, which is 582 00:28:13,200 --> 00:28:18,700 the product H3O plus and OH minus. 583 00:28:18,700 --> 00:28:20,680 And you can do the math. 584 00:28:20,680 --> 00:28:23,480 That's 10 to the minus 14 is the product. 585 00:28:23,480 --> 00:28:27,310 And you can use the common ion effect here. 586 00:28:27,310 --> 00:28:29,960 If I introduce some other acid, look at how this 587 00:28:29,960 --> 00:28:32,670 equation helps you the same way that Ksp did. 588 00:28:32,670 --> 00:28:36,460 If I have acid, in other words, protons donated from 589 00:28:36,460 --> 00:28:39,180 some other source, that means this number is going to be 590 00:28:39,180 --> 00:28:41,000 higher than 10 to the minus 7. 591 00:28:41,000 --> 00:28:43,470 If this number is higher than 10 to the minus 7, and the 592 00:28:43,470 --> 00:28:47,200 product must be 10 to the minus 14, this must be lower. 593 00:28:47,200 --> 00:28:53,950 So when I have, H3O plus goes up, then OH minus must go 594 00:28:53,950 --> 00:28:56,650 down, and under these circumstances, we have 595 00:28:56,650 --> 00:28:58,960 something that is called proton-rich. 596 00:28:58,960 --> 00:29:02,060 597 00:29:02,060 --> 00:29:06,240 And we call this acid, simply because the proton 598 00:29:06,240 --> 00:29:08,370 concentration exceeds the hydroxyl. 599 00:29:08,370 --> 00:29:10,630 And likewise for the other. 600 00:29:10,630 --> 00:29:15,480 And so we can make a plot of this, and that's shown here. 601 00:29:15,480 --> 00:29:19,440 And all we've got is OH versus H3O plus. 602 00:29:19,440 --> 00:29:23,540 And you can see that it's a right hyperbola. 603 00:29:23,540 --> 00:29:27,610 But it goes back to that comment that I made in the 604 00:29:27,610 --> 00:29:29,900 past about how you graph data. 605 00:29:29,900 --> 00:29:33,030 I don't know what to do with that, because it's curved. 606 00:29:33,030 --> 00:29:36,330 I can't tell whether the data are good or bad. 607 00:29:36,330 --> 00:29:40,330 So instead of looking at something like this, y versus 608 00:29:40,330 --> 00:29:43,890 x, I want to transform so that can get a straight line. 609 00:29:43,890 --> 00:29:46,720 Because then I can make a judgment about goodness 610 00:29:46,720 --> 00:29:47,780 of fit and so on. 611 00:29:47,780 --> 00:29:52,870 So I need some f of x versus g of y to, quote unquote, 612 00:29:52,870 --> 00:29:53,930 straighten this out. 613 00:29:53,930 --> 00:29:59,540 And we have that, thanks to another Dane, 614 00:29:59,540 --> 00:30:01,930 by the name of Sorensen. 615 00:30:01,930 --> 00:30:05,050 Sorensen was the one that gave us another way 616 00:30:05,050 --> 00:30:06,810 to think about it. 617 00:30:06,810 --> 00:30:13,590 Sorensen, who in 1901, and he's got the DK on his-- 618 00:30:13,590 --> 00:30:14,830 he's probably got a Volvo, too. 619 00:30:14,830 --> 00:30:16,520 Or maybe he's driving a Saab. 620 00:30:16,520 --> 00:30:19,620 So he was a biochemist at the Carlsberg brewery. 621 00:30:19,620 --> 00:30:22,930 Yes, they had biochemists, because they wanted understand 622 00:30:22,930 --> 00:30:25,670 the chemistry of beer production. 623 00:30:25,670 --> 00:30:26,570 What a concept. 624 00:30:26,570 --> 00:30:27,850 Having people that understand the 625 00:30:27,850 --> 00:30:29,960 technology of the business. 626 00:30:29,960 --> 00:30:32,580 So he was working at the Carlsberg brewery, and he 627 00:30:32,580 --> 00:30:37,390 decided to take this acid-base business and turn it into 628 00:30:37,390 --> 00:30:41,810 something that's much more readily recognizable. 629 00:30:41,810 --> 00:30:49,030 And so he defined a concept called the chemical potential, 630 00:30:49,030 --> 00:30:53,850 which, if you like, is the reactivity, the chemical 631 00:30:53,850 --> 00:30:55,250 potential of hydronium. 632 00:30:55,250 --> 00:30:58,720 633 00:30:58,720 --> 00:30:59,980 And he gave it the symbol. 634 00:30:59,980 --> 00:31:04,950 Lowercase p for potential, and uppercase H as, obviously, for 635 00:31:04,950 --> 00:31:06,790 the hydrogen ion. 636 00:31:06,790 --> 00:31:09,970 And he said, I'm going to make this a logarithm. 637 00:31:09,970 --> 00:31:12,820 So it's logarithm, and in those days, everybody was 638 00:31:12,820 --> 00:31:17,780 using slide rules, so it's log base 10 of the concentration 639 00:31:17,780 --> 00:31:19,010 of hydronium. 640 00:31:19,010 --> 00:31:21,650 And being a good engineer, he recognized since this starts 641 00:31:21,650 --> 00:31:26,050 off at 10 to the minus 7, the log of a number less than one 642 00:31:26,050 --> 00:31:27,930 is going to be negative. 643 00:31:27,930 --> 00:31:29,700 And who wants to deal with negative numbers? 644 00:31:29,700 --> 00:31:31,260 So you put a minus sign here. 645 00:31:31,260 --> 00:31:34,610 That way, pH normally is a positive number. 646 00:31:34,610 --> 00:31:39,020 And now you can see the results of Sorensen's 647 00:31:39,020 --> 00:31:40,585 straightening things out for us. 648 00:31:40,585 --> 00:31:43,220 So now you go over a wider range, and you can see, you 649 00:31:43,220 --> 00:31:45,220 have nice straight line relationship, and then you can 650 00:31:45,220 --> 00:31:47,040 get data on there, and so on. 651 00:31:47,040 --> 00:31:49,990 And this is taken from your book, and it shows the pH 652 00:31:49,990 --> 00:31:52,830 values of some common substances. 653 00:31:52,830 --> 00:31:56,690 If you start here at neutral pH 7, you have milk, you have 654 00:31:56,690 --> 00:32:00,650 human blood, normal things that you would expect, fluids 655 00:32:00,650 --> 00:32:02,950 and so on, are hovering around 7. 656 00:32:02,950 --> 00:32:04,690 If you take some coffee, you're going to go into the 657 00:32:04,690 --> 00:32:05,370 acidic region. 658 00:32:05,370 --> 00:32:07,780 You see tomatoes down here at about 4. 659 00:32:07,780 --> 00:32:12,705 Wine, you'll see in the reviews of wines, they'll say 660 00:32:12,705 --> 00:32:14,770 it has balanced acidity and so on. 661 00:32:14,770 --> 00:32:16,830 Yeah, it's down around pH 3. 662 00:32:16,830 --> 00:32:21,040 And carbonated soft drinks, some of them get down to 2. 663 00:32:21,040 --> 00:32:23,020 Vinegar is wine that has spoiled. 664 00:32:23,020 --> 00:32:25,630 Vin aigre, which means eager. 665 00:32:25,630 --> 00:32:27,140 The Middle French eager meant 666 00:32:27,140 --> 00:32:29,660 impetuous, or tart, or something. 667 00:32:29,660 --> 00:32:31,070 So this is spoiled wine. 668 00:32:31,070 --> 00:32:32,310 And the pH changes. 669 00:32:32,310 --> 00:32:35,720 So by measuring the pH of wine, you can tell if it's 670 00:32:35,720 --> 00:32:36,580 changing or not. 671 00:32:36,580 --> 00:32:37,400 There's lemon juice. 672 00:32:37,400 --> 00:32:41,840 Gastric juices in the stomach can get down to 1, pH of 1. 673 00:32:41,840 --> 00:32:43,950 But you want that happening only at one point in the 674 00:32:43,950 --> 00:32:45,300 digestive cycle. 675 00:32:45,300 --> 00:32:48,930 If you run around for long periods of time at pH 1, you 676 00:32:48,930 --> 00:32:51,700 will ulcerate, in other words, you'll puncture the walls. 677 00:32:51,700 --> 00:32:55,740 And if that's about to happen, you need to neutralize. 678 00:32:55,740 --> 00:32:56,790 So how do you neutralize? 679 00:32:56,790 --> 00:32:58,750 You go up with something that has a high pH. 680 00:32:58,750 --> 00:33:01,200 So you can start with something like Alka-Seltzer, 681 00:33:01,200 --> 00:33:04,130 sodium bicarbonate at about 8.4, or milk 682 00:33:04,130 --> 00:33:05,950 of magnesia, 10.5. 683 00:33:05,950 --> 00:33:07,820 Why is it milk of magnesia? 684 00:33:07,820 --> 00:33:10,830 From last day, because it's not a solution, it is a 685 00:33:10,830 --> 00:33:11,700 suspension. 686 00:33:11,700 --> 00:33:14,320 The magnesia is in suspension. 687 00:33:14,320 --> 00:33:15,710 The magnesium hydroxide. 688 00:33:15,710 --> 00:33:18,860 And that's one of those mandatory shake well before 689 00:33:18,860 --> 00:33:22,330 using, because all the magnesia is on the bottom, and 690 00:33:22,330 --> 00:33:25,910 you've got this almost clear, colorless liquid on the top. 691 00:33:25,910 --> 00:33:27,390 So you're just drinking water. 692 00:33:27,390 --> 00:33:29,960 Not going to help you if you've got stomach pain, but 693 00:33:29,960 --> 00:33:31,620 gastric juice is down here. 694 00:33:31,620 --> 00:33:34,180 If you're really desperate, don't reach for ammonia. 695 00:33:34,180 --> 00:33:36,140 You have to be patient. 696 00:33:36,140 --> 00:33:39,320 They have to work with milk of magnesia. 697 00:33:39,320 --> 00:33:39,660 OK. 698 00:33:39,660 --> 00:33:40,910 So that's the range. 699 00:33:40,910 --> 00:33:43,860 700 00:33:43,860 --> 00:33:47,520 So what else do we have here? 701 00:33:47,520 --> 00:33:50,850 Let's take a look. 702 00:33:50,850 --> 00:33:56,570 So far we've been assuming that when we add acid to the 703 00:33:56,570 --> 00:33:59,680 system, we get 1 to 1 dissociation. 704 00:33:59,680 --> 00:34:03,730 So the next message that I want to give you here, is that 705 00:34:03,730 --> 00:34:05,983 not all acids are of equal strength. 706 00:34:05,983 --> 00:34:15,510 707 00:34:15,510 --> 00:34:18,890 See, I could look up here and say, well, maybe the reason 708 00:34:18,890 --> 00:34:22,970 that the lemon juice is down it at 2 and the gastric juices 709 00:34:22,970 --> 00:34:26,170 are at 1 is simply a concentration effect. 710 00:34:26,170 --> 00:34:28,790 How much acid was introduced. 711 00:34:28,790 --> 00:34:31,240 No, there's another explanation for it. 712 00:34:31,240 --> 00:34:34,670 And that is that certain acids don't fully disassociate. 713 00:34:34,670 --> 00:34:40,220 So for example, if we look at 1 molar HCl, hydrochloric 714 00:34:40,220 --> 00:34:44,480 acid, you look at 1 molar hydrochloric acid, that goes 715 00:34:44,480 --> 00:34:49,880 100% into solution and gives us 1 molar H30 plus. 716 00:34:49,880 --> 00:34:53,450 So 1 to 1 correspondence between how much hydrochloric 717 00:34:53,450 --> 00:34:57,760 acid we introduce, and how much 718 00:34:57,760 --> 00:34:59,760 hydroxyl that we generate. 719 00:34:59,760 --> 00:35:07,160 So this is total dissociation of the HCl. 720 00:35:07,160 --> 00:35:10,105 And as a result, we call this a strong acid. 721 00:35:10,105 --> 00:35:13,410 722 00:35:13,410 --> 00:35:15,890 In contrast, let me show you a weak acid. 723 00:35:15,890 --> 00:35:18,210 So a weak acid is going to dissolve, but it doesn't 724 00:35:18,210 --> 00:35:18,880 dissociate. 725 00:35:18,880 --> 00:35:20,530 So there's really two steps here. 726 00:35:20,530 --> 00:35:23,160 First you've got to get the stuff in solution, and then 727 00:35:23,160 --> 00:35:26,330 once you get it in solution, it has to break apart. 728 00:35:26,330 --> 00:35:29,165 It's possible to go into solution and not break apart. 729 00:35:29,165 --> 00:35:32,140 In which case, you don't have the protons, but you've got 730 00:35:32,140 --> 00:35:33,520 the solution. 731 00:35:33,520 --> 00:35:34,470 That's not an acid. 732 00:35:34,470 --> 00:35:37,700 So a weak acid would be, let's, in contrast, 733 00:35:37,700 --> 00:35:39,070 look at a weak acid. 734 00:35:39,070 --> 00:35:40,930 A weak acid would be something like acetic 735 00:35:40,930 --> 00:35:44,210 acid, which is CH3COOH. 736 00:35:44,210 --> 00:35:45,760 And this is for historical reasons. 737 00:35:45,760 --> 00:35:49,580 Normally, the proton that's going to dissociate is at the 738 00:35:49,580 --> 00:35:53,890 front of the formula, but this was written long ago, before 739 00:35:53,890 --> 00:35:55,170 people understood this theory. 740 00:35:55,170 --> 00:35:57,990 And that's the way you'll see acetic acid written. 741 00:35:57,990 --> 00:36:02,280 So really, this is the proton, and the CH3COO is really the 742 00:36:02,280 --> 00:36:06,310 acetate anion, Ac, acetate anion. 743 00:36:06,310 --> 00:36:10,230 So we're going to put that into solution, like this. 744 00:36:10,230 --> 00:36:13,140 I'm going to put it into water, H20 liquid. 745 00:36:13,140 --> 00:36:18,005 So this is the salt out of solution, and all we're going 746 00:36:18,005 --> 00:36:23,210 to do is make it into the aqueous solution of same COOH, 747 00:36:23,210 --> 00:36:26,060 and I'm just going to write aq. 748 00:36:26,060 --> 00:36:28,880 Now, if this were strong acid with impunity, I would write 749 00:36:28,880 --> 00:36:33,030 whatever the concentration of acetic acid is, I break it 750 00:36:33,030 --> 00:36:35,400 apart, and I get the full amount of the proton. 751 00:36:35,400 --> 00:36:44,340 What happens is that this, now plus H20, gives me H3O plus 752 00:36:44,340 --> 00:36:49,480 plus the remaining acetate, which is CH3COO minus. 753 00:36:49,480 --> 00:36:53,410 And now, here's where the weakness is manifested. 754 00:36:53,410 --> 00:36:59,850 The degree to which the acetic acid grabs protons from here, 755 00:36:59,850 --> 00:37:01,910 and then ends up being protonated, 756 00:37:01,910 --> 00:37:03,440 is very, very small. 757 00:37:03,440 --> 00:37:06,310 It turns out that in the case of 1 molar-- 758 00:37:06,310 --> 00:37:10,570 759 00:37:10,570 --> 00:37:12,360 I'm going to write acetic acid this way, now. 760 00:37:12,360 --> 00:37:14,100 HAc. 761 00:37:14,100 --> 00:37:19,880 So this thing here is the CH3COO minus, all right? 762 00:37:19,880 --> 00:37:25,240 It turns out that in 1 molar acetic acid, we 763 00:37:25,240 --> 00:37:29,400 get only 0.4% reaction. 764 00:37:29,400 --> 00:37:33,915 0.4% reacts and dissociates. 765 00:37:33,915 --> 00:37:38,180 766 00:37:38,180 --> 00:37:44,060 So to give protons, it hangs onto most of its protons. 767 00:37:44,060 --> 00:37:47,690 So we can then represent this in the form of an acid 768 00:37:47,690 --> 00:37:49,045 dissociation constant. 769 00:37:49,045 --> 00:37:57,850 770 00:37:57,850 --> 00:37:58,970 And that it looks like this. 771 00:37:58,970 --> 00:38:01,730 K sub a for acid. 772 00:38:01,730 --> 00:38:05,100 So on the right side, what we're going to do is make a 773 00:38:05,100 --> 00:38:06,460 mass balance here. 774 00:38:06,460 --> 00:38:08,930 We're going to take the product of the proton, the 775 00:38:08,930 --> 00:38:14,010 acetate divided by the undisassociated acetic acid. 776 00:38:14,010 --> 00:38:18,210 So we'll put H3O plus concentration times the 777 00:38:18,210 --> 00:38:21,690 acetate concentration divided by the 778 00:38:21,690 --> 00:38:26,350 undissociated HAc aqueous. 779 00:38:26,350 --> 00:38:31,290 So I'm trying to represent what the ratio is here. 780 00:38:31,290 --> 00:38:35,890 And instead of being one to one, it's 10 to the minus 5. 781 00:38:35,890 --> 00:38:37,290 Very, very weak. 782 00:38:37,290 --> 00:38:39,080 You get a little bit, but not much. 783 00:38:39,080 --> 00:38:42,260 Now, you could say, well, 10 to the minus 5, this is, just 784 00:38:42,260 --> 00:38:46,050 for reference, it's 100 times 10 to the minus 7, 785 00:38:46,050 --> 00:38:47,190 which is the Kw. 786 00:38:47,190 --> 00:38:50,750 So the point here is, if you put in acetic acid, you'll end 787 00:38:50,750 --> 00:38:53,590 up with 100 times the proton population that you would have 788 00:38:53,590 --> 00:38:56,090 had by just self-dissociation. 789 00:38:56,090 --> 00:38:57,100 So it isn't acid. 790 00:38:57,100 --> 00:38:58,410 It is donating protons. 791 00:38:58,410 --> 00:39:01,230 But it's not doing it a lot. 792 00:39:01,230 --> 00:39:03,610 So this is called a weak acid, because it's 793 00:39:03,610 --> 00:39:06,635 a poor proton donor. 794 00:39:06,635 --> 00:39:09,950 795 00:39:09,950 --> 00:39:14,620 And so we can then look at a comparison to, 796 00:39:14,620 --> 00:39:16,580 say, over here, HCl. 797 00:39:16,580 --> 00:39:20,370 Let's go back here, and we can write the acid dissociation 798 00:39:20,370 --> 00:39:23,830 constant for HCl, for the strong acid. 799 00:39:23,830 --> 00:39:27,280 And in that case, Ka over here, which is going to be the 800 00:39:27,280 --> 00:39:31,610 H3O plus Cl minus, H3O plus. 801 00:39:31,610 --> 00:39:35,310 In the case of HCl, we're going to get proton and 802 00:39:35,310 --> 00:39:44,910 chloride over undissociated HCl dissolved in water. 803 00:39:44,910 --> 00:39:48,820 And that's 10 to the plus 6, which for all intents and 804 00:39:48,820 --> 00:39:50,680 purposes is infinity. 805 00:39:50,680 --> 00:39:55,300 You put in 1 molar HCl, you get 1 molar H plus. 806 00:39:55,300 --> 00:39:56,210 And look at the ratio. 807 00:39:56,210 --> 00:39:58,810 10 to the sixth, 10 to the minus 5. 808 00:39:58,810 --> 00:40:03,770 There's a 10 to the eleventh relationship between the weak 809 00:40:03,770 --> 00:40:05,890 acid and the strong acid. 810 00:40:05,890 --> 00:40:09,420 And here's the cartoon that shows this strong acid, put in 811 00:40:09,420 --> 00:40:12,240 this amount, 100% dissociation, weak acid gives 812 00:40:12,240 --> 00:40:16,680 you small amounts of proton, and a very weak acid is 813 00:40:16,680 --> 00:40:19,370 imperceptible amount of disassociation. 814 00:40:19,370 --> 00:40:21,170 And here's a table that quantifies it. 815 00:40:21,170 --> 00:40:24,760 So the strong acids up here with the Ka. 816 00:40:24,760 --> 00:40:28,600 This value of Ka has to be greater than 1, because it's 817 00:40:28,600 --> 00:40:31,540 saying that we're getting a lot of dissociation, the 818 00:40:31,540 --> 00:40:32,870 reactions moving to the right. 819 00:40:32,870 --> 00:40:33,860 And you have these numbers here. 820 00:40:33,860 --> 00:40:36,360 10 to the ninth, 10 to the eighth, 10 to the sixth. 821 00:40:36,360 --> 00:40:38,060 Those are differences without distinction. 822 00:40:38,060 --> 00:40:40,650 if I say the ratio is a million to one, or a billion 823 00:40:40,650 --> 00:40:43,500 to one, for all intents and purposes, you have 824 00:40:43,500 --> 00:40:44,610 dissociation. 825 00:40:44,610 --> 00:40:45,840 And then here are the week acids. 826 00:40:45,840 --> 00:40:46,070 Look. 827 00:40:46,070 --> 00:40:47,420 10 to the minus 3. 828 00:40:47,420 --> 00:40:50,820 There's phosphoric, hydrofluoric, and so on, all 829 00:40:50,820 --> 00:40:51,400 the way down. 830 00:40:51,400 --> 00:40:54,140 There's carbonic acid, 10 to the minus 7. 831 00:40:54,140 --> 00:40:56,890 So there's the list. 832 00:40:56,890 --> 00:41:01,330 And just another cute demonstration of the 833 00:41:01,330 --> 00:41:07,330 relationship between bonding and acidity, the acid strength 834 00:41:07,330 --> 00:41:11,130 increases from left to right, and the bond strength 835 00:41:11,130 --> 00:41:13,180 increases from right to left. 836 00:41:13,180 --> 00:41:14,940 You know, HF is very strong. 837 00:41:14,940 --> 00:41:16,090 It's a hydrogen-bonded. 838 00:41:16,090 --> 00:41:18,390 Very tight HF bond. 839 00:41:18,390 --> 00:41:20,620 But what determines if it's going to be a 840 00:41:20,620 --> 00:41:22,260 strong acid or not? 841 00:41:22,260 --> 00:41:26,590 It's how willing HF is to give up its H. 842 00:41:26,590 --> 00:41:28,710 But its H is tightly bound. 843 00:41:28,710 --> 00:41:32,440 So oddly enough, in HF, you don't give up much of the H. 844 00:41:32,440 --> 00:41:33,880 HF is over here. 845 00:41:33,880 --> 00:41:35,170 It's less than one. 846 00:41:35,170 --> 00:41:36,500 It's a weak acid. 847 00:41:36,500 --> 00:41:38,310 HCl is a pretty strong acid. 848 00:41:38,310 --> 00:41:43,020 If you want to go heavy-duty, HBr and HI are even stronger 849 00:41:43,020 --> 00:41:46,630 acids, because they have a weaker hold on the hydrogen 850 00:41:46,630 --> 00:41:49,600 within them, so they are much, much more 851 00:41:49,600 --> 00:41:51,760 generous proton donors. 852 00:41:51,760 --> 00:41:53,490 So you can see that from there. 853 00:41:53,490 --> 00:41:54,990 OK. 854 00:41:54,990 --> 00:41:58,110 So what's the takeaway message here? 855 00:41:58,110 --> 00:42:07,010 The takeaway message is that equal acid concentration does 856 00:42:07,010 --> 00:42:08,760 not mean equal acid strength. 857 00:42:08,760 --> 00:42:11,210 You have to be mediated by the Ka. 858 00:42:11,210 --> 00:42:14,420 Equal acid concentration, which means, how 859 00:42:14,420 --> 00:42:16,010 much did you dissolve? 860 00:42:16,010 --> 00:42:22,510 Does not equal acid strength. 861 00:42:22,510 --> 00:42:23,510 And what's the reason? 862 00:42:23,510 --> 00:42:26,140 Because equal acid concentration, this is a 863 00:42:26,140 --> 00:42:30,090 function of solubility, whereas this is a function of 864 00:42:30,090 --> 00:42:31,090 dissociation. 865 00:42:31,090 --> 00:42:34,160 So many dissolve, few dissociate. 866 00:42:34,160 --> 00:42:34,830 How about that? 867 00:42:34,830 --> 00:42:37,600 There's a nice tagline you can use. 868 00:42:37,600 --> 00:42:39,180 Use that at a party this weekend. 869 00:42:39,180 --> 00:42:41,130 Many dissolve, but few dissociate. 870 00:42:41,130 --> 00:42:41,450 All right. 871 00:42:41,450 --> 00:42:43,120 Now I want to go very, very high. 872 00:42:43,120 --> 00:42:44,590 Big concept, all right? 873 00:42:44,590 --> 00:42:48,330 Last definition of acid-base comes from the United States. 874 00:42:48,330 --> 00:42:48,450 G. 875 00:42:48,450 --> 00:42:48,740 N. 876 00:42:48,740 --> 00:42:50,820 Lewis. 877 00:42:50,820 --> 00:42:51,150 Same G. 878 00:42:51,150 --> 00:42:51,370 N. 879 00:42:51,370 --> 00:42:55,310 Lewis who gave us the Lewis cross and dot structures, 880 00:42:55,310 --> 00:42:58,080 covalent bonding, didn't stop inventing. 881 00:42:58,080 --> 00:43:01,280 So we're going to put U.S.A., with a Chevrolet out in 882 00:43:01,280 --> 00:43:02,470 California. 883 00:43:02,470 --> 00:43:03,190 And what did G. 884 00:43:03,190 --> 00:43:03,430 N. 885 00:43:03,430 --> 00:43:04,550 Lewis tell us? 886 00:43:04,550 --> 00:43:08,950 He said, I want to extend the Bronsted-Lowry concept. 887 00:43:08,950 --> 00:43:10,485 But you know, let me give you an analogy. 888 00:43:10,485 --> 00:43:12,140 Have you ever stood on a bridge and 889 00:43:12,140 --> 00:43:14,150 watched the traffic go? 890 00:43:14,150 --> 00:43:16,750 You see it starts from a stop sign or a traffic light. 891 00:43:16,750 --> 00:43:20,140 Light turns green, the first car pulls away, the second car 892 00:43:20,140 --> 00:43:23,020 pulls away, the third car pulls away. 893 00:43:23,020 --> 00:43:25,370 The other way you can look at it is, when the first car 894 00:43:25,370 --> 00:43:27,600 pulls away, there's a car vacancy. 895 00:43:27,600 --> 00:43:31,150 And instead of watching the cars go from right to left, 896 00:43:31,150 --> 00:43:34,440 watch the car vacancy move from left to right. 897 00:43:34,440 --> 00:43:35,980 And the two are linked. 898 00:43:35,980 --> 00:43:39,030 And point of fact, if you're the fourth car from the 899 00:43:39,030 --> 00:43:40,630 traffic light, light turns green and you 900 00:43:40,630 --> 00:43:42,350 hit the horn, why? 901 00:43:42,350 --> 00:43:43,350 You can't drive. 902 00:43:43,350 --> 00:43:46,020 You have to drive only into a car vacancy, and it takes time 903 00:43:46,020 --> 00:43:48,130 for the car vacancy to get to you. 904 00:43:48,130 --> 00:43:52,340 When the rate of vacancy flux is not matched by the rate of 905 00:43:52,340 --> 00:43:55,340 car flux, then we have a collision, and then we 906 00:43:55,340 --> 00:43:56,220 exchange papers. 907 00:43:56,220 --> 00:43:58,570 So it's a mass transport problem. 908 00:43:58,570 --> 00:43:59,315 So now what G. 909 00:43:59,315 --> 00:43:59,500 N. 910 00:43:59,500 --> 00:44:05,620 Lewis said was, instead of looking at this reaction as a 911 00:44:05,620 --> 00:44:10,470 proton transfer reaction, and looking at proton attachment, 912 00:44:10,470 --> 00:44:13,680 or proton acquisition, he said, why don't we look at 913 00:44:13,680 --> 00:44:17,390 this from the other side of the relationship? 914 00:44:17,390 --> 00:44:20,860 And so he said, let's look at something like, for example, 915 00:44:20,860 --> 00:44:22,640 we've got NH3 here. 916 00:44:22,640 --> 00:44:27,910 So let's put the N with the 2 electrons. 917 00:44:27,910 --> 00:44:31,300 And we've been talking about this from the perspective of 918 00:44:31,300 --> 00:44:34,980 the bond being formed here through the 919 00:44:34,980 --> 00:44:37,360 acquisition of the proton. 920 00:44:37,360 --> 00:44:40,790 Lewis said, I can view this from the other perspective, 921 00:44:40,790 --> 00:44:42,490 and say, I'm going to view it from the 922 00:44:42,490 --> 00:44:43,850 perspective of the nitrogen. 923 00:44:43,850 --> 00:44:46,620 From the perspective of the nitrogen, this reaction 924 00:44:46,620 --> 00:44:51,690 represents the donation of the electron pair. 925 00:44:51,690 --> 00:44:53,440 A very high concept. 926 00:44:53,440 --> 00:44:57,890 So this base is not about proton attachment. 927 00:44:57,890 --> 00:45:01,390 It's about donating an electronic pair. 928 00:45:01,390 --> 00:45:04,270 So let's get that down, because that's really good. 929 00:45:04,270 --> 00:45:08,400 So I'm going to say something that's a base looks like this. 930 00:45:08,400 --> 00:45:09,840 This is what a base is. 931 00:45:09,840 --> 00:45:11,920 It's a lone pair. 932 00:45:11,920 --> 00:45:15,355 This is electron pair, very high level base. 933 00:45:15,355 --> 00:45:18,130 934 00:45:18,130 --> 00:45:20,900 And what's the proton give us? 935 00:45:20,900 --> 00:45:22,520 What we're doing, is we're talking about 936 00:45:22,520 --> 00:45:24,430 electrons and donation. 937 00:45:24,430 --> 00:45:27,990 So what's this other thing in that same category? 938 00:45:27,990 --> 00:45:33,740 An electron pair can match up with an empty orbital. 939 00:45:33,740 --> 00:45:36,110 That's the only place electron pairs can go. 940 00:45:36,110 --> 00:45:37,840 They go to the empty orbitals. 941 00:45:37,840 --> 00:45:41,060 So electron pair is a base, and this is just a circle 942 00:45:41,060 --> 00:45:42,410 around nothing. 943 00:45:42,410 --> 00:45:42,910 OK? 944 00:45:42,910 --> 00:45:44,170 This is nothing. 945 00:45:44,170 --> 00:45:46,050 But it's a special kind of nothing. 946 00:45:46,050 --> 00:45:47,510 This is called a vacant orbital. 947 00:45:47,510 --> 00:45:52,660 948 00:45:52,660 --> 00:45:56,150 And I'm going to call a vacant orbital an acid, in the most 949 00:45:56,150 --> 00:45:57,840 general sense. 950 00:45:57,840 --> 00:46:00,220 So now I'm going to take an electron pair plus vacant 951 00:46:00,220 --> 00:46:03,700 orbital, and what did they react to give me? 952 00:46:03,700 --> 00:46:06,990 Covalent bond. 953 00:46:06,990 --> 00:46:08,035 You'd expect that from G. 954 00:46:08,035 --> 00:46:08,240 N. 955 00:46:08,240 --> 00:46:12,600 Lewis, because G. 956 00:46:12,600 --> 00:46:12,960 N. 957 00:46:12,960 --> 00:46:14,570 Lewis enunciated covalency. 958 00:46:14,570 --> 00:46:15,873 That's why you'd expect it from G. 959 00:46:15,873 --> 00:46:15,976 N. 960 00:46:15,976 --> 00:46:16,340 Lewis. 961 00:46:16,340 --> 00:46:19,750 So this is, vacant orbital plus electron pair gives 962 00:46:19,750 --> 00:46:20,820 covalent bond. 963 00:46:20,820 --> 00:46:22,430 Very high level. 964 00:46:22,430 --> 00:46:23,450 Very high level. 965 00:46:23,450 --> 00:46:25,190 So what is a base? 966 00:46:25,190 --> 00:46:31,080 A base is now not just a proton acceptor. 967 00:46:31,080 --> 00:46:38,040 It's an electron pair donor, and the acid is an electron 968 00:46:38,040 --> 00:46:39,290 pair acceptor. 969 00:46:39,290 --> 00:46:42,100 970 00:46:42,100 --> 00:46:44,130 So now there's no chemistry here. 971 00:46:44,130 --> 00:46:46,280 No chemical identities. 972 00:46:46,280 --> 00:46:49,190 Which means, I can even go from-- 973 00:46:49,190 --> 00:46:50,620 I don't even have to be in solution. 974 00:46:50,620 --> 00:46:52,240 I don't have to be in a liquid. 975 00:46:52,240 --> 00:46:54,670 This could be a gas and a solid. 976 00:46:54,670 --> 00:46:56,080 Could be a gas plus a gas. 977 00:46:56,080 --> 00:46:57,790 So this is, like, Darwinian. 978 00:46:57,790 --> 00:46:59,940 You know, we've come out of the primordial ooze, and now 979 00:46:59,940 --> 00:47:03,310 we can fly, because we can talk about any chemical 980 00:47:03,310 --> 00:47:04,480 reaction we want. 981 00:47:04,480 --> 00:47:06,820 Any state of matter. 982 00:47:06,820 --> 00:47:08,590 It's fantastic. 983 00:47:08,590 --> 00:47:09,680 Absolutely fantastic. 984 00:47:09,680 --> 00:47:13,210 So here, let me do one last color drawing. 985 00:47:13,210 --> 00:47:14,990 We want to do this one here. 986 00:47:14,990 --> 00:47:18,030 This is Lewis and the biggest concept. 987 00:47:18,030 --> 00:47:19,570 So we're going to go like this. 988 00:47:19,570 --> 00:47:23,120 Base like this. 989 00:47:23,120 --> 00:47:26,620 Base with its lone pair hanging out 990 00:47:26,620 --> 00:47:31,110 plus acid gives us-- 991 00:47:31,110 --> 00:47:31,760 three colors. 992 00:47:31,760 --> 00:47:32,370 This is great. 993 00:47:32,370 --> 00:47:35,100 We've got all this colored chalk, it's Friday, 994 00:47:35,100 --> 00:47:36,070 what could be better. 995 00:47:36,070 --> 00:47:37,680 All right. 996 00:47:37,680 --> 00:47:44,470 So now we're going to end up with A, B, there it is. 997 00:47:44,470 --> 00:47:46,340 This is the Lewis concept. 998 00:47:46,340 --> 00:47:53,400 Lewis acid-base concept. 999 00:47:53,400 --> 00:47:54,310 In the broadest thing. 1000 00:47:54,310 --> 00:47:55,460 Now I'm going to show you an example of 1001 00:47:55,460 --> 00:47:57,090 how you can use this. 1002 00:47:57,090 --> 00:47:58,000 I'm not going to stop here. 1003 00:47:58,000 --> 00:47:59,410 OK, let's go. 1004 00:47:59,410 --> 00:47:59,720 All right. 1005 00:47:59,720 --> 00:48:01,240 So we're going to talk about acid rain 1006 00:48:01,240 --> 00:48:02,870 from burning of coal. 1007 00:48:02,870 --> 00:48:05,210 You know, about half of the electric power in this country 1008 00:48:05,210 --> 00:48:09,930 comes from burning coal, and coal contains about 1% sulfur. 1009 00:48:09,930 --> 00:48:14,290 You can purify it of sulfur, but it takes money to do so. 1010 00:48:14,290 --> 00:48:16,640 A ton of coal will give you about 25 million British 1011 00:48:16,640 --> 00:48:20,130 thermal units, and that's the number in SI units and joules. 1012 00:48:20,130 --> 00:48:23,890 So 3 tons of coal will give you 1 megawatt per day. 1013 00:48:23,890 --> 00:48:26,070 By the way, it takes about one gram of uranium 1014 00:48:26,070 --> 00:48:26,880 to do the same thing. 1015 00:48:26,880 --> 00:48:28,170 So someday, when you're sitting there as a 1016 00:48:28,170 --> 00:48:31,450 policymaker, you've got a choice of 3 tons of coal or 1017 00:48:31,450 --> 00:48:34,290 one gram of uranium, keep this fact in mind. 1018 00:48:34,290 --> 00:48:37,690 A 10 megawatt plant burns 30 tons of coal per day, 1019 00:48:37,690 --> 00:48:41,160 containing a third of a ton of sulphur, which makes 2/3 of a 1020 00:48:41,160 --> 00:48:43,230 ton of SO2. 1021 00:48:43,230 --> 00:48:46,600 And SO2 is a precursor to acid rain. 1022 00:48:46,600 --> 00:48:50,520 Now we can reduce that SO2 emissions by reacting SO2 with 1023 00:48:50,520 --> 00:48:53,140 a lime, CaO, according to this reaction, to 1024 00:48:53,140 --> 00:48:55,610 make calcium sulfite. 1025 00:48:55,610 --> 00:48:58,170 And now I'm going to bring in this. 1026 00:48:58,170 --> 00:48:59,430 Lewis. 1027 00:48:59,430 --> 00:49:02,390 Oh, here's from your textbook, there's the scrubbers with the 1028 00:49:02,390 --> 00:49:05,010 calcium oxide, and water missed, and so on, and 1029 00:49:05,010 --> 00:49:08,810 eventually they trap the SO2. 1030 00:49:08,810 --> 00:49:10,210 They do nothing to the CO2. 1031 00:49:10,210 --> 00:49:13,510 So all the CO2 is going up. 1032 00:49:13,510 --> 00:49:16,060 So here's calcium oxide, which is a solid. 1033 00:49:16,060 --> 00:49:17,100 It's lime. 1034 00:49:17,100 --> 00:49:19,990 You know, stuff you sprinkle on football fields. 1035 00:49:19,990 --> 00:49:22,460 And this is SO2, and it's got this structure with the 1036 00:49:22,460 --> 00:49:24,750 resident bond double single. 1037 00:49:24,750 --> 00:49:27,940 The oxygen here acts the way it did in the 1038 00:49:27,940 --> 00:49:29,490 glasses, as a modifier. 1039 00:49:29,490 --> 00:49:31,580 It goes in and breaks this double bond, and now we have 1040 00:49:31,580 --> 00:49:33,900 three single bonds. 1041 00:49:33,900 --> 00:49:37,090 So we can look at this from Lewis acid-base. 1042 00:49:37,090 --> 00:49:39,960 You know, calcium oxides, electron pair donor. 1043 00:49:39,960 --> 00:49:42,880 If it's an electron pair donor, it's a base. 1044 00:49:42,880 --> 00:49:43,720 So it's a base. 1045 00:49:43,720 --> 00:49:47,250 And you know SO2 better be an acid, or your theory is nuts, 1046 00:49:47,250 --> 00:49:49,340 because SO2 is a precursor to acid rain. 1047 00:49:49,340 --> 00:49:50,670 So it has to be an acid. 1048 00:49:50,670 --> 00:49:52,450 It's an electronic pair acceptor, 1049 00:49:52,450 --> 00:49:53,390 which is what we said. 1050 00:49:53,390 --> 00:49:54,660 It's an electron pair acceptor. 1051 00:49:54,660 --> 00:49:58,020 So this is a Lewis acid-base reaction that 1052 00:49:58,020 --> 00:49:59,770 is a gas-solid reaction. 1053 00:49:59,770 --> 00:50:03,050 So we started with aqueous solutions, and we end up 1054 00:50:03,050 --> 00:50:05,790 generalizing all of these types of reactions. 1055 00:50:05,790 --> 00:50:07,360 So that's pretty good. 1056 00:50:07,360 --> 00:50:12,270 Here's a plot of acid concentration 1057 00:50:12,270 --> 00:50:14,280 up in the sky, here. 1058 00:50:14,280 --> 00:50:17,140 You're Here. 1059 00:50:17,140 --> 00:50:18,410 Yeah. 1060 00:50:18,410 --> 00:50:22,790 Last thing I'll do, I talked a lot about Lavoisier and 1061 00:50:22,790 --> 00:50:24,250 Scheele and Priestley. 1062 00:50:24,250 --> 00:50:26,310 This is a play, if you've got the little bit 1063 00:50:26,310 --> 00:50:27,220 of time this weekend. 1064 00:50:27,220 --> 00:50:28,130 You might try reading it. 1065 00:50:28,130 --> 00:50:30,760 This is Carl Djerassi and Roald Hoffman, both Nobel 1066 00:50:30,760 --> 00:50:32,440 Prize winners in Chemistry. 1067 00:50:32,440 --> 00:50:33,260 Not the same year. 1068 00:50:33,260 --> 00:50:36,340 They won independent Nobel Prizes, and actually speak to 1069 00:50:36,340 --> 00:50:39,010 each other, and they collaborated on this play. 1070 00:50:39,010 --> 00:50:41,000 Here's the setup, the premise. 1071 00:50:41,000 --> 00:50:43,150 The premise of the play is that the Nobel committee 1072 00:50:43,150 --> 00:50:47,380 decides to give Nobel Prizes retrograde. 1073 00:50:47,380 --> 00:50:48,600 Before 1901. 1074 00:50:48,600 --> 00:50:51,740 You see, you can't get a Nobel Prize posthumously. 1075 00:50:51,740 --> 00:50:54,070 You've got to do something great, and you've got to keep 1076 00:50:54,070 --> 00:50:56,670 on living until you get the prize. 1077 00:50:56,670 --> 00:50:58,590 So they decided they're going to go backwards, you know, 1078 00:50:58,590 --> 00:51:01,250 maybe give prizes to people like, I don't know, Maxwell or 1079 00:51:01,250 --> 00:51:02,800 Faraday or whatever. 1080 00:51:02,800 --> 00:51:05,370 And they decide, it should be simple in the old days. 1081 00:51:05,370 --> 00:51:07,790 Because we didn't have all this dog-eat-dog competition 1082 00:51:07,790 --> 00:51:10,530 in science, and big grants, and corporate interests. 1083 00:51:10,530 --> 00:51:11,790 Should be simple. 1084 00:51:11,790 --> 00:51:17,670 Until they hit the Nobel Prize for the discovery of oxygen. 1085 00:51:17,670 --> 00:51:20,000 And then they hit the wall with these three different 1086 00:51:20,000 --> 00:51:21,080 competitors. 1087 00:51:21,080 --> 00:51:24,120 And so the story goes that the three competitors and their 1088 00:51:24,120 --> 00:51:26,440 wives end up in Stockholm, and the 1089 00:51:26,440 --> 00:51:28,100 interactions the take place. 1090 00:51:28,100 --> 00:51:31,350 And it's really fascinating, because you have Lavoisier, 1091 00:51:31,350 --> 00:51:34,260 who was the political conservative but the chemical 1092 00:51:34,260 --> 00:51:39,320 radical, Priestley, who was the chemical radical but the 1093 00:51:39,320 --> 00:51:40,650 political conservative-- 1094 00:51:40,650 --> 00:51:41,710 by the way, Lavoisier. 1095 00:51:41,710 --> 00:51:43,190 You know how he died? 1096 00:51:43,190 --> 00:51:45,800 He was guillotined during the French revolution. 1097 00:51:45,800 --> 00:51:48,630 And people think it's because he was a tax collector. 1098 00:51:48,630 --> 00:51:49,450 Not true. 1099 00:51:49,450 --> 00:51:51,210 He was a tax collector. 1100 00:51:51,210 --> 00:51:55,070 The real reason is Marat, who was one of the chief justices 1101 00:51:55,070 --> 00:51:59,220 of the Jacobin terror, was also a scientist. And around 1102 00:51:59,220 --> 00:52:03,380 1740, Marat had submitted an article for publication, and 1103 00:52:03,380 --> 00:52:04,430 it was rejected. 1104 00:52:04,430 --> 00:52:08,710 And Lavoisier was on the editorial board. 1105 00:52:08,710 --> 00:52:11,910 And so sometimes when I get an article to review, and I have 1106 00:52:11,910 --> 00:52:15,680 to give it a negative review, I think about this story. 1107 00:52:15,680 --> 00:52:19,490 And sometimes, I will just say, you know, I'm really busy 1108 00:52:19,490 --> 00:52:24,060 teaching 3091 and I won't get to this on a timely basis. 1109 00:52:24,060 --> 00:52:24,730 OK, people. 1110 00:52:24,730 --> 00:52:25,980 Have a nice weekend. 1111 00:52:25,980 --> 00:52:37,358