1 00:00:00,000 --> 00:00:01,968 [SQUEAKING] 2 00:00:01,968 --> 00:00:03,936 [RUSTLING] 3 00:00:03,936 --> 00:00:06,396 [CLICKING] 4 00:00:15,200 --> 00:00:16,200 SARAH HEWETT: All right. 5 00:00:16,200 --> 00:00:17,670 We can probably get started. 6 00:00:17,670 --> 00:00:19,310 So good afternoon. 7 00:00:19,310 --> 00:00:23,723 And today, we are going to start talking about the final lab 8 00:00:23,723 --> 00:00:25,640 that we are going to talk about in the lecture 9 00:00:25,640 --> 00:00:27,057 and the final lab that you haven't 10 00:00:27,057 --> 00:00:29,870 heard about yet for the course, which is the catalase lab. 11 00:00:29,870 --> 00:00:31,910 And some of you guys started that yesterday. 12 00:00:31,910 --> 00:00:33,470 And some of you will start it today. 13 00:00:33,470 --> 00:00:35,803 And then the rest of you will have to wait a little bit. 14 00:00:35,803 --> 00:00:40,490 But the catalase lab is our biochemistry type lab that we 15 00:00:40,490 --> 00:00:42,110 were doing in 5.310. 16 00:00:42,110 --> 00:00:46,040 And catalase is an enzyme if you couldn't tell by the name. 17 00:00:46,040 --> 00:00:47,510 A lot of enzyme names-- 18 00:00:47,510 --> 00:00:50,600 you guys are familiar from your biology classes-- end in ase. 19 00:00:50,600 --> 00:00:52,310 So catalase is an enzyme. 20 00:00:52,310 --> 00:00:55,970 And enzymes are proteins-- just a review of your general bio-- 21 00:00:55,970 --> 00:00:58,100 that carry out specific chemical reactions. 22 00:00:58,100 --> 00:01:00,470 And they're produced by different living organisms. 23 00:01:00,470 --> 00:01:06,380 They work in the cells to do a very wide range of chemistry. 24 00:01:06,380 --> 00:01:09,632 And there are many different graphical representations, 25 00:01:09,632 --> 00:01:11,840 weird pictures that you can find on the internet that 26 00:01:11,840 --> 00:01:14,445 try to depict what an enzyme actually does in cartoon form. 27 00:01:14,445 --> 00:01:16,320 And so here are a couple of examples of that. 28 00:01:16,320 --> 00:01:17,990 So you have your enzyme and then you have 29 00:01:17,990 --> 00:01:18,960 what's called your substrate. 30 00:01:18,960 --> 00:01:21,380 And so that is the thing that the enzyme is doing chemistry 31 00:01:21,380 --> 00:01:21,880 on. 32 00:01:21,880 --> 00:01:23,000 The substrate comes in. 33 00:01:23,000 --> 00:01:26,630 It interacts with your enzyme to form an enzyme substrate 34 00:01:26,630 --> 00:01:27,725 complex. 35 00:01:27,725 --> 00:01:28,850 Then the chemistry happens. 36 00:01:28,850 --> 00:01:31,000 And then the enzyme releases the product. 37 00:01:31,000 --> 00:01:34,750 So sometimes the products will be rearranging the substrate. 38 00:01:34,750 --> 00:01:36,500 Sometimes it will be taking two substrates 39 00:01:36,500 --> 00:01:37,310 and joining them together. 40 00:01:37,310 --> 00:01:38,870 And sometimes it will be taking one substrate 41 00:01:38,870 --> 00:01:39,740 and breaking it apart. 42 00:01:39,740 --> 00:01:41,448 So there's a bunch of different reactions 43 00:01:41,448 --> 00:01:43,267 that can happen in different enzymes. 44 00:01:43,267 --> 00:01:45,350 Similar thing-- if you want to look at your enzyme 45 00:01:45,350 --> 00:01:47,630 as a little Pacman kind of guy. 46 00:01:47,630 --> 00:01:49,432 You form the enzyme substrate complex. 47 00:01:49,432 --> 00:01:50,390 You form your products. 48 00:01:50,390 --> 00:01:52,510 And then they break apart. 49 00:01:52,510 --> 00:01:55,380 So that's the general idea of how enzymes 50 00:01:55,380 --> 00:01:59,260 works in a very quick nutshell. 51 00:01:59,260 --> 00:02:01,440 So our specific enzyme is catalase. 52 00:02:01,440 --> 00:02:05,670 And here are a couple of pictures of catalase or artist 53 00:02:05,670 --> 00:02:07,290 renditions of catalase. 54 00:02:07,290 --> 00:02:09,180 So this is a space filling model of what 55 00:02:09,180 --> 00:02:12,450 it would look like if all of the atoms were kind of 3D balls. 56 00:02:12,450 --> 00:02:15,540 So you can see it has four different subdomains here. 57 00:02:15,540 --> 00:02:18,900 And then these darker parts in the middle 58 00:02:18,900 --> 00:02:21,157 with the little green dot, those are your heme center, 59 00:02:21,157 --> 00:02:22,740 so these are iron molecules and that's 60 00:02:22,740 --> 00:02:23,580 where the chemistry happens. 61 00:02:23,580 --> 00:02:25,680 So these are the active sites of the catalase. 62 00:02:25,680 --> 00:02:29,357 And you can also-- you may have seen in other courses proteins 63 00:02:29,357 --> 00:02:31,440 represented like this, which has a little bit more 64 00:02:31,440 --> 00:02:33,870 of the features of their secondary and tertiary 65 00:02:33,870 --> 00:02:34,780 structure. 66 00:02:34,780 --> 00:02:36,210 So you can see the alpha helices and beta sheets. 67 00:02:36,210 --> 00:02:38,190 And we're going to talk more about the structure 68 00:02:38,190 --> 00:02:40,190 of the active site and how the chemistry happens 69 00:02:40,190 --> 00:02:43,800 and what all of those squiggles mean next week 70 00:02:43,800 --> 00:02:45,170 when we talk about catalase. 71 00:02:45,170 --> 00:02:47,220 AUDIENCE: [INAUDIBLE] 72 00:02:48,930 --> 00:02:49,830 SARAH HEWETT: Yes. 73 00:02:49,830 --> 00:02:50,730 Or wait. 74 00:02:50,730 --> 00:02:53,280 Each sub-domain has one active site. 75 00:02:53,280 --> 00:02:56,503 So it has one heme in each of the four parts. 76 00:02:56,503 --> 00:02:58,170 And we'll talk more about that next week 77 00:02:58,170 --> 00:03:00,870 when we go a little bit deeper into the structure of catalase 78 00:03:00,870 --> 00:03:02,123 and how it works. 79 00:03:02,123 --> 00:03:03,540 And then the other important thing 80 00:03:03,540 --> 00:03:07,080 you need to know about catalase is it's a large molecule. 81 00:03:07,080 --> 00:03:08,130 Proteins generally are. 82 00:03:08,130 --> 00:03:10,900 There are polypeptides-- lots and lots of amino acids. 83 00:03:10,900 --> 00:03:14,110 And so its weight is 240 kilodaltons. 84 00:03:14,110 --> 00:03:18,130 And a kilodalton is 1,000 mass units. 85 00:03:18,130 --> 00:03:21,230 So it's 240,000 grams per mole. 86 00:03:21,230 --> 00:03:22,980 And you'll need that for some calculations 87 00:03:22,980 --> 00:03:24,855 that you'll do in the second half of the lab. 88 00:03:24,855 --> 00:03:27,330 And we'll go over that again in the next lecture. 89 00:03:27,330 --> 00:03:29,880 But to give you an idea of the size 90 00:03:29,880 --> 00:03:34,360 of that thing and the molar mass, it is very large. 91 00:03:34,360 --> 00:03:35,690 Why do we need catalase? 92 00:03:35,690 --> 00:03:38,347 So there are many redox reactions 93 00:03:38,347 --> 00:03:40,930 that are happening in your body where you do electron transfer 94 00:03:40,930 --> 00:03:43,900 reactions and you oxidize or reduce different things 95 00:03:43,900 --> 00:03:45,340 in your metabolism. 96 00:03:45,340 --> 00:03:47,710 And so electrons are transferred around cells. 97 00:03:47,710 --> 00:03:50,170 You may have heard of the molecule NADPH or NADH. 98 00:03:50,170 --> 00:03:54,130 Those transfer electrons between different molecules 99 00:03:54,130 --> 00:03:55,918 in your cells and help with metabolism. 100 00:03:55,918 --> 00:03:58,210 And while these electrons are being transferred around, 101 00:03:58,210 --> 00:03:59,710 you also know that we breathe oxygen 102 00:03:59,710 --> 00:04:01,585 and we need oxygen to do-- to perform 103 00:04:01,585 --> 00:04:02,710 many of our life processes. 104 00:04:02,710 --> 00:04:05,125 So you have a lot of oxygen in your body as well. 105 00:04:05,125 --> 00:04:07,000 And during a lot of these metabolic processes 106 00:04:07,000 --> 00:04:10,890 you can get electrons that are transferred to oxygen. 107 00:04:10,890 --> 00:04:18,649 So if we have our oxygen and it gains an electron, 108 00:04:18,649 --> 00:04:20,480 we have what is called superoxide. 109 00:04:20,480 --> 00:04:22,010 So now this has a negative charge 110 00:04:22,010 --> 00:04:24,230 and an unpaired electron. 111 00:04:24,230 --> 00:04:26,270 And so it is a superoxide radical. 112 00:04:26,270 --> 00:04:28,925 And what do we know about radicals? 113 00:04:28,925 --> 00:04:30,350 AUDIENCE: [INAUDIBLE] 114 00:04:30,350 --> 00:04:32,300 SARAH HEWETT: They would like to be stable. 115 00:04:32,300 --> 00:04:34,610 So they are not stable because they 116 00:04:34,610 --> 00:04:35,820 have this unpaired electrons. 117 00:04:35,820 --> 00:04:37,640 So they will either give up this electron 118 00:04:37,640 --> 00:04:39,557 or try to take an electron from something else 119 00:04:39,557 --> 00:04:42,560 in order to have their electron be-- 120 00:04:42,560 --> 00:04:45,150 or not be unpaired anymore. 121 00:04:45,150 --> 00:04:47,630 So these are very reactive in the body. 122 00:04:47,630 --> 00:04:49,442 And this is actually a problem. 123 00:04:49,442 --> 00:04:50,900 And we don't want this in our cells 124 00:04:50,900 --> 00:04:51,983 because it is so reactive. 125 00:04:51,983 --> 00:04:54,740 So there is another enzyme called superoxide dismutase 126 00:04:54,740 --> 00:04:57,650 that breaks this apart into elemental oxygen 127 00:04:57,650 --> 00:05:00,110 and oddly enough hydrogen peroxide. 128 00:05:00,110 --> 00:05:01,970 But it turns out that hydrogen peroxide 129 00:05:01,970 --> 00:05:04,640 in high enough concentrations is also toxic to your cells. 130 00:05:04,640 --> 00:05:08,820 And hydrogen peroxide can form hydroxy radicals, 131 00:05:08,820 --> 00:05:10,880 which are also very damaging to your cells. 132 00:05:10,880 --> 00:05:13,610 There's a couple of reactions that hydrogen peroxide 133 00:05:13,610 --> 00:05:15,995 can do in the body. 134 00:05:15,995 --> 00:05:17,870 So the first is if you have hydrogen peroxide 135 00:05:17,870 --> 00:05:21,810 and then you have some of this superoxide around-- 136 00:05:21,810 --> 00:05:25,140 so it's a radical anion there. 137 00:05:25,140 --> 00:05:36,480 You can make oxygen, hydroxide ions, which are OK, 138 00:05:36,480 --> 00:05:39,690 and then hydroxy radicals. 139 00:05:39,690 --> 00:05:42,660 So then you form more radicals and those can go and damage 140 00:05:42,660 --> 00:05:45,360 your DNA, your proteins, the different fatty acids 141 00:05:45,360 --> 00:05:47,395 in your body, and cause all kinds of problems. 142 00:05:47,395 --> 00:05:49,770 Another thing that can happen is if there's just hydrogen 143 00:05:49,770 --> 00:05:57,720 peroxide around and it picks up an electron, it can form water 144 00:05:57,720 --> 00:06:03,380 and another hydroxyl radical. 145 00:06:03,380 --> 00:06:05,270 So these are the reactions that we do not 146 00:06:05,270 --> 00:06:08,330 want to happen in our body because it forms these-- 147 00:06:08,330 --> 00:06:09,620 it just keeps propagating. 148 00:06:09,620 --> 00:06:13,070 And then when radicals react with other things that have all 149 00:06:13,070 --> 00:06:15,380 paired electrons, it generates more radicals 150 00:06:15,380 --> 00:06:17,120 and you propagate the radical formation 151 00:06:17,120 --> 00:06:19,800 throughout your cell it causes a lot of damage. 152 00:06:19,800 --> 00:06:23,600 So we need a way to get rid of the hydrogen 153 00:06:23,600 --> 00:06:27,080 peroxide in our body and that is what catalase is for. 154 00:06:27,080 --> 00:06:29,480 And all organisms have catalase. 155 00:06:29,480 --> 00:06:32,690 You can extract it out of humans, all types of mammals, 156 00:06:32,690 --> 00:06:34,280 even plants have it. 157 00:06:34,280 --> 00:06:36,160 Cells do not want hydrogen peroxide in them. 158 00:06:36,160 --> 00:06:37,827 So there are different forms of catalase 159 00:06:37,827 --> 00:06:41,160 that you can get from any organism-- bacteria, all 160 00:06:41,160 --> 00:06:41,660 the things. 161 00:06:41,660 --> 00:06:43,827 The catalase that we're going to be using in the lab 162 00:06:43,827 --> 00:06:45,470 was extracted from cows. 163 00:06:45,470 --> 00:06:46,640 So just a fun fact. 164 00:06:49,960 --> 00:06:52,113 And when we're talking about enzymes, 165 00:06:52,113 --> 00:06:54,280 the reason that enzymes are so good and so efficient 166 00:06:54,280 --> 00:06:56,770 at their jobs is because they catalyze chemical reactions. 167 00:06:56,770 --> 00:06:58,437 And a lot of you are chemical engineers, 168 00:06:58,437 --> 00:07:00,250 so you probably know about catalysis. 169 00:07:00,250 --> 00:07:02,417 So what does it mean for something to be a catalyst? 170 00:07:06,410 --> 00:07:07,398 Anyone? 171 00:07:07,398 --> 00:07:09,190 Please give me a quick catalyst definition. 172 00:07:09,190 --> 00:07:09,920 AUDIENCE: [INAUDIBLE] reaction. 173 00:07:09,920 --> 00:07:10,160 SARAH HEWETT: Yeah. 174 00:07:10,160 --> 00:07:11,330 It speeds up a chemical reaction. 175 00:07:11,330 --> 00:07:13,030 And it's not used up during the process. 176 00:07:13,030 --> 00:07:20,128 So if we look at our energy reaction diagram, 177 00:07:20,128 --> 00:07:22,170 if you have energy on this side and then reaction 178 00:07:22,170 --> 00:07:24,578 progress on this axis, you can say 179 00:07:24,578 --> 00:07:27,120 that you have reactants that are starting at a certain energy 180 00:07:27,120 --> 00:07:28,300 level. 181 00:07:28,300 --> 00:07:31,113 And then you have some energy that you 182 00:07:31,113 --> 00:07:33,030 have to put into the reaction to get it to go. 183 00:07:33,030 --> 00:07:36,240 And then in a lot of cases, if your reaction is exothermic, 184 00:07:36,240 --> 00:07:38,580 your products maybe at a lower energy level. 185 00:07:38,580 --> 00:07:40,327 So it'll release energy overall. 186 00:07:40,327 --> 00:07:41,910 But in order to get the reaction to go 187 00:07:41,910 --> 00:07:43,110 you have to put energy in. 188 00:07:43,110 --> 00:07:48,833 So this part of the curve is our delta H of our reaction. 189 00:07:48,833 --> 00:07:50,250 So it would be the energy released 190 00:07:50,250 --> 00:07:54,150 if it's exothermic, which in this case this reaction is. 191 00:07:54,150 --> 00:07:56,723 But no matter what you need to put in some energy 192 00:07:56,723 --> 00:07:58,140 to get the reaction to go and this 193 00:07:58,140 --> 00:08:00,870 is called the activation energy. 194 00:08:09,170 --> 00:08:12,770 Occasionally abbreviated E sub a. 195 00:08:12,770 --> 00:08:14,600 So this is what we care about when 196 00:08:14,600 --> 00:08:16,370 we're talking about reaction kinetics 197 00:08:16,370 --> 00:08:19,670 and what a catalyst does. 198 00:08:19,670 --> 00:08:22,610 So a catalyst functions and it makes the reaction faster 199 00:08:22,610 --> 00:08:25,070 by lowering this energy barrier. 200 00:08:25,070 --> 00:08:28,100 So if the yellow line is the reaction without a catalyst, 201 00:08:28,100 --> 00:08:33,083 then with a catalyst it will be smaller. 202 00:08:33,083 --> 00:08:34,500 And the products and the reactants 203 00:08:34,500 --> 00:08:37,287 will have the same total energy, but the energy 204 00:08:37,287 --> 00:08:39,120 you need to put in to get the reaction to go 205 00:08:39,120 --> 00:08:42,455 is going to be less. 206 00:08:42,455 --> 00:08:43,830 And so the reaction can go faster 207 00:08:43,830 --> 00:08:45,360 and it can go in milder conditions. 208 00:08:45,360 --> 00:08:49,140 And we can talk about how enzymes 209 00:08:49,140 --> 00:08:51,310 work to lower this activation energy. 210 00:08:51,310 --> 00:08:54,030 So does anybody know what methods enzymes 211 00:08:54,030 --> 00:08:56,770 use to lower the activation energy of a reaction? 212 00:08:56,770 --> 00:08:57,270 Yes? 213 00:08:57,270 --> 00:08:58,103 AUDIENCE: Proximity? 214 00:08:58,103 --> 00:08:59,940 Just getting the reactants together? 215 00:08:59,940 --> 00:09:00,732 SARAH HEWETT: Yeah. 216 00:09:00,732 --> 00:09:01,423 Proximity. 217 00:09:01,423 --> 00:09:03,090 So it gets the reactants close together. 218 00:09:06,397 --> 00:09:07,980 If you have your reactants in a beaker 219 00:09:07,980 --> 00:09:08,820 and they're all floating around, they 220 00:09:08,820 --> 00:09:10,470 have to find each other before they can react. 221 00:09:10,470 --> 00:09:11,610 And so if you have an enzyme that 222 00:09:11,610 --> 00:09:13,235 has a specifically designed active site 223 00:09:13,235 --> 00:09:15,760 to hold these two molecules close together, 224 00:09:15,760 --> 00:09:17,460 then they will react. 225 00:09:17,460 --> 00:09:19,973 What else? 226 00:09:19,973 --> 00:09:21,890 AUDIENCE: It can stabilize a transition state? 227 00:09:21,890 --> 00:09:22,682 SARAH HEWETT: Yeah. 228 00:09:22,682 --> 00:09:26,130 It can stabilize a transition state. 229 00:09:26,130 --> 00:09:28,918 And how does it do that? 230 00:09:28,918 --> 00:09:32,648 AUDIENCE: [INAUDIBLE] 231 00:09:32,648 --> 00:09:33,440 SARAH HEWETT: Yeah. 232 00:09:33,440 --> 00:09:35,697 So it bonds to the substrate and it 233 00:09:35,697 --> 00:09:38,030 can have either electrostatic or even sometimes covalent 234 00:09:38,030 --> 00:09:39,080 interactions. 235 00:09:39,080 --> 00:09:40,890 And it stabilizes the transition state. 236 00:09:40,890 --> 00:09:42,682 And part of the way that it does that is it 237 00:09:42,682 --> 00:09:45,403 holds the molecules in the right orientation for them to react. 238 00:09:45,403 --> 00:09:46,820 So even if you have two molecules, 239 00:09:46,820 --> 00:09:48,903 if they're supposed to interact like this to react 240 00:09:48,903 --> 00:09:50,990 and they're in a beaker and they hit on this side 241 00:09:50,990 --> 00:09:54,060 or upside down, the reaction will not happen. 242 00:09:54,060 --> 00:09:55,790 So we can stabilize transition states. 243 00:10:00,310 --> 00:10:06,550 Your transition state and put molecules 244 00:10:06,550 --> 00:10:07,800 in the correct orientation. 245 00:10:15,020 --> 00:10:16,310 Anything else? 246 00:10:16,310 --> 00:10:18,430 There is one more thing that they can do. 247 00:10:22,820 --> 00:10:23,320 OK. 248 00:10:23,320 --> 00:10:24,250 What's your idea? 249 00:10:24,250 --> 00:10:28,630 AUDIENCE: If they raise the temperature, it will increase-- 250 00:10:28,630 --> 00:10:31,245 collisions could increase. 251 00:10:31,245 --> 00:10:33,620 SARAH HEWETT: So increasing the temperature of a reaction 252 00:10:33,620 --> 00:10:34,662 will get it to go faster. 253 00:10:34,662 --> 00:10:36,348 Right? 254 00:10:36,348 --> 00:10:37,890 But that's just because then you will 255 00:10:37,890 --> 00:10:40,170 have more molecules that have the necessary activation 256 00:10:40,170 --> 00:10:40,540 energy. 257 00:10:40,540 --> 00:10:42,873 So you're not necessarily lowering the activation energy 258 00:10:42,873 --> 00:10:45,182 that the reaction needs. 259 00:10:45,182 --> 00:10:46,640 But the last thing that they can do 260 00:10:46,640 --> 00:10:49,040 is they can provide alternate reaction pathways. 261 00:10:58,220 --> 00:11:01,280 So sometimes you may think that this will just 262 00:11:01,280 --> 00:11:03,560 be a one-step reaction. 263 00:11:03,560 --> 00:11:06,110 If you had an enzyme, occasionally it'll 264 00:11:06,110 --> 00:11:06,770 look like this. 265 00:11:06,770 --> 00:11:09,735 It might provide an extra intermediate in there 266 00:11:09,735 --> 00:11:11,360 that helps to lower the overall energy. 267 00:11:11,360 --> 00:11:12,735 And so that's another way that it 268 00:11:12,735 --> 00:11:14,787 can lower this overall activation energy 269 00:11:14,787 --> 00:11:16,370 is by providing an alternate mechanism 270 00:11:16,370 --> 00:11:20,820 other than maybe just two molecules reacting together. 271 00:11:20,820 --> 00:11:22,410 There might be a third intermediate 272 00:11:22,410 --> 00:11:24,970 that helps actually lower the overall energy. 273 00:11:24,970 --> 00:11:29,040 So those are possible ways that the enzymes can work 274 00:11:29,040 --> 00:11:30,940 to lower the activation energy. 275 00:11:30,940 --> 00:11:35,502 And so our goals for the catalase lab are-- 276 00:11:35,502 --> 00:11:37,210 well, there are a few goals that we have. 277 00:11:37,210 --> 00:11:38,920 But our goals for days one and two 278 00:11:38,920 --> 00:11:42,550 are to determine the activation energy of hydrogen-- 279 00:11:42,550 --> 00:11:46,240 the decomposition of hydrogen peroxide as catalyzed 280 00:11:46,240 --> 00:11:47,980 by the catalase enzyme. 281 00:11:47,980 --> 00:11:50,200 So we're going to try and figure out 282 00:11:50,200 --> 00:11:52,240 what the activation energy is after it's already 283 00:11:52,240 --> 00:11:53,410 been catalyzed. 284 00:11:53,410 --> 00:11:55,780 And in order to do this, we are going 285 00:11:55,780 --> 00:11:57,970 to need to first determine the order of the reaction 286 00:11:57,970 --> 00:11:59,345 with respect to hydrogen peroxide 287 00:11:59,345 --> 00:12:01,860 and be able to write a rate law. 288 00:12:01,860 --> 00:12:03,715 That'll help us characterize the kinetics. 289 00:12:03,715 --> 00:12:05,090 So in day one of this lab, you're 290 00:12:05,090 --> 00:12:06,257 going to do that first part. 291 00:12:06,257 --> 00:12:09,460 And you're going to figure out what the order of the reaction 292 00:12:09,460 --> 00:12:09,960 is. 293 00:12:09,960 --> 00:12:13,050 And in order to have that make any sense 294 00:12:13,050 --> 00:12:16,020 we need to talk about kinetics and how we discuss kinetics 295 00:12:16,020 --> 00:12:17,758 in a chemical sense. 296 00:12:17,758 --> 00:12:20,050 So kinetics deals with the speed of chemical reactions. 297 00:12:20,050 --> 00:12:22,260 And if we use everybody's favorite generic reaction 298 00:12:22,260 --> 00:12:24,170 a plus b goes to c plus d. 299 00:12:24,170 --> 00:12:26,670 You can write the rate of this reaction-- you can express it 300 00:12:26,670 --> 00:12:28,333 in a number of ways. 301 00:12:28,333 --> 00:12:30,000 So the first way is to think of the rate 302 00:12:30,000 --> 00:12:34,300 of the reaction as the change in the reactants over time-- 303 00:12:34,300 --> 00:12:35,010 so a and b. 304 00:12:35,010 --> 00:12:36,608 And it has a negative sign because you 305 00:12:36,608 --> 00:12:37,650 are losing the reactants. 306 00:12:37,650 --> 00:12:41,200 Hopefully they're going away as the reaction progresses. 307 00:12:41,200 --> 00:12:45,040 And it is equal to the rate of the appearance 308 00:12:45,040 --> 00:12:46,402 of c and the appearance of d. 309 00:12:46,402 --> 00:12:47,860 So these do not have negative signs 310 00:12:47,860 --> 00:12:50,578 because you are making your product. 311 00:12:50,578 --> 00:12:52,870 So that is one way to express the rate of the reaction. 312 00:12:52,870 --> 00:12:57,110 And when you do it this way, you need to account for the fact 313 00:12:57,110 --> 00:12:58,890 that there are different molar ratios. 314 00:12:58,890 --> 00:13:00,980 So the reactants and the products 315 00:13:00,980 --> 00:13:02,838 will disappear in form at different rates 316 00:13:02,838 --> 00:13:05,130 depending on how many of them you need in the reaction. 317 00:13:05,130 --> 00:13:07,338 So to account for that, we multiply by the reciprocal 318 00:13:07,338 --> 00:13:09,810 of this coefficient. 319 00:13:09,810 --> 00:13:11,310 We can also write a generic rate law 320 00:13:11,310 --> 00:13:15,157 like this where your rate equals your rate constant, which 321 00:13:15,157 --> 00:13:16,740 you can calculate and determine in lab 322 00:13:16,740 --> 00:13:18,310 and is dependent on the temperature 323 00:13:18,310 --> 00:13:20,310 times the concentration of your reactants raised 324 00:13:20,310 --> 00:13:22,283 to a power and your concentration 325 00:13:22,283 --> 00:13:24,450 of your other reactants raised to a different power. 326 00:13:27,160 --> 00:13:32,320 And you can also write an integrated rate law, 327 00:13:32,320 --> 00:13:33,740 which you may have seen before. 328 00:13:33,740 --> 00:13:36,620 So integrated rate laws deal with one reactant at a time. 329 00:13:36,620 --> 00:13:39,490 And so if we look at a, we can say-- we can write-- 330 00:13:39,490 --> 00:13:42,760 if there's only a we can write the rate of a equals the rate 331 00:13:42,760 --> 00:13:44,500 constant times a. 332 00:13:44,500 --> 00:13:47,125 Or we can say that the rate is equal to the disappearance 333 00:13:47,125 --> 00:13:49,030 of a overtime. 334 00:13:49,030 --> 00:13:52,010 And you can take the derivative of this. 335 00:13:52,010 --> 00:13:55,090 So if we move everything over, rearrange it-- 336 00:14:07,090 --> 00:14:10,490 So if we integrate both sides of this-- 337 00:14:10,490 --> 00:14:14,750 if we integrate this side from your initial concentration 338 00:14:14,750 --> 00:14:17,720 to your concentration at some temperature 339 00:14:17,720 --> 00:14:24,140 and this side from t equals 0 to some time t, 340 00:14:24,140 --> 00:14:30,545 then if you do that math out you will get the natural log of-- 341 00:14:37,510 --> 00:14:44,060 this is your integrated rate law if your exponent here equals 1. 342 00:14:44,060 --> 00:14:46,770 So obviously, that will change if you have different exponents 343 00:14:46,770 --> 00:14:47,270 here. 344 00:14:47,270 --> 00:14:48,410 And then when you do your integration 345 00:14:48,410 --> 00:14:49,660 you will get different values. 346 00:14:49,660 --> 00:14:52,620 But this is a way to relate the concentration 347 00:14:52,620 --> 00:14:54,620 at your initial concentration to a concentration 348 00:14:54,620 --> 00:14:58,413 at a final temperature or a final time. 349 00:14:58,413 --> 00:15:00,080 So that's one thing that you've probably 350 00:15:00,080 --> 00:15:04,170 seen before in some of your other chemistry classes. 351 00:15:04,170 --> 00:15:06,643 And we can also talk about-- 352 00:15:06,643 --> 00:15:08,310 well, we'll talk about that in a second. 353 00:15:10,970 --> 00:15:14,050 You may also have seen in some of your other classes enzyme 354 00:15:14,050 --> 00:15:16,630 kinetics or heard of Michaelis-Menten kinetics. 355 00:15:16,630 --> 00:15:19,060 And the Michaelis-Menten model of enzyme kinetics 356 00:15:19,060 --> 00:15:20,770 says that if you have an enzyme and you 357 00:15:20,770 --> 00:15:24,760 have a bunch of substrate, the reaction can only 358 00:15:24,760 --> 00:15:26,980 go as fast as there is when there's only one 359 00:15:26,980 --> 00:15:28,030 substrate in each enzyme. 360 00:15:28,030 --> 00:15:31,450 So if all of the active sites are full of substrate, 361 00:15:31,450 --> 00:15:34,150 then that is as fast as the reaction can go. 362 00:15:34,150 --> 00:15:35,930 And it will proceed at a steady state. 363 00:15:35,930 --> 00:15:38,380 So you can make graphs of the reaction 364 00:15:38,380 --> 00:15:40,490 rate versus how much concentration of substrate 365 00:15:40,490 --> 00:15:41,290 you have. 366 00:15:41,290 --> 00:15:44,660 And you can get this Michaelis-Menten constant here, 367 00:15:44,660 --> 00:15:50,530 which is a measure of how much the enzyme-- 368 00:15:50,530 --> 00:15:53,060 what its affinity is for the substrate essentially. 369 00:15:53,060 --> 00:15:56,590 So does the enzyme need a whole bunch of substrate 370 00:15:56,590 --> 00:15:58,310 before it'll start going quickly? 371 00:15:58,310 --> 00:15:59,980 Or can it go quickly and efficiently 372 00:15:59,980 --> 00:16:02,240 with just a tiny concentration of substrate? 373 00:16:02,240 --> 00:16:03,850 So we're not going to worry so much 374 00:16:03,850 --> 00:16:08,950 about those parameters for our lab right now. 375 00:16:08,950 --> 00:16:11,890 But this is something you may have seen. 376 00:16:11,890 --> 00:16:14,680 And one of the assumptions of the Michaelis-Menten kinetics, 377 00:16:14,680 --> 00:16:16,640 which is actually kind of important to us 378 00:16:16,640 --> 00:16:18,640 is that you have your enzyme and your substrate. 379 00:16:18,640 --> 00:16:20,265 They make the enzyme substrate complex. 380 00:16:20,265 --> 00:16:22,330 And then they go to enzyme and product. 381 00:16:22,330 --> 00:16:24,320 And they don't go in the reverse reaction. 382 00:16:24,320 --> 00:16:25,420 So that's kind of important to us 383 00:16:25,420 --> 00:16:27,920 that if we are trying to measure the rates of our reactions, 384 00:16:27,920 --> 00:16:30,850 that we don't have to contend with the reactions being 385 00:16:30,850 --> 00:16:31,810 catalyzed in reverse. 386 00:16:35,540 --> 00:16:37,160 All right. 387 00:16:37,160 --> 00:16:39,160 So now we can take a little bit of a closer look 388 00:16:39,160 --> 00:16:43,690 at the rate law for just a normal chemical reaction. 389 00:16:43,690 --> 00:16:45,685 And pretty much the most important thing 390 00:16:45,685 --> 00:16:48,060 you want to know about this is that the units of the rate 391 00:16:48,060 --> 00:16:51,040 are always moles per liter per second. 392 00:16:51,040 --> 00:16:53,970 So whenever you are trying to calculate a rate constant, 393 00:16:53,970 --> 00:16:57,760 you want your units to line up. 394 00:16:57,760 --> 00:17:05,810 So if your rate-- 395 00:17:05,810 --> 00:17:11,480 if we want this in molarity per second-- 396 00:17:11,480 --> 00:17:13,250 if your rate equals-- 397 00:17:13,250 --> 00:17:18,170 let's say these are both equal to 1 just for now. 398 00:17:21,000 --> 00:17:24,500 Then what are our units over here? 399 00:17:24,500 --> 00:17:26,990 M and M. So what are the units of k have to be? 400 00:17:35,650 --> 00:17:38,150 So that's how you can figure out what the units of your rate 401 00:17:38,150 --> 00:17:40,460 constant are because it always needs 402 00:17:40,460 --> 00:17:44,360 to multiply with your concentrations and your k 403 00:17:44,360 --> 00:17:46,370 to equal moles per liter per second. 404 00:17:46,370 --> 00:17:48,500 And that is going to be the units of our rate 405 00:17:48,500 --> 00:17:51,595 that we care about in our kinetic equations. 406 00:17:51,595 --> 00:17:53,970 The rate constant is different at different temperatures. 407 00:17:53,970 --> 00:17:56,012 So if you change the temperature of the reaction, 408 00:17:56,012 --> 00:17:57,860 then your rate constant will change 409 00:17:57,860 --> 00:17:59,527 and you'll have to remeasure that. 410 00:17:59,527 --> 00:18:01,610 And x and y are values that need to be determined. 411 00:18:01,610 --> 00:18:04,890 They may be the same as little a and little b but not always. 412 00:18:04,890 --> 00:18:06,890 So the kinetics of a reaction are 413 00:18:06,890 --> 00:18:08,870 determined if it's a multi-step reaction 414 00:18:08,870 --> 00:18:12,050 if their reaction mechanism has more than one part in it. 415 00:18:12,050 --> 00:18:16,150 They may not all be reflected in this overall chemical equation. 416 00:18:16,150 --> 00:18:18,730 You may not see them, but the rate 417 00:18:18,730 --> 00:18:21,070 is going to be dependent on your slowest step. 418 00:18:21,070 --> 00:18:23,140 And that slowest step is what is going 419 00:18:23,140 --> 00:18:24,470 to determine your rate law. 420 00:18:24,470 --> 00:18:27,410 And it may not always match your overall reaction equation. 421 00:18:27,410 --> 00:18:31,000 So be careful when you are determining these things. 422 00:18:31,000 --> 00:18:32,650 You can't always just assume that it is 423 00:18:32,650 --> 00:18:37,100 from the little a and little b. 424 00:18:37,100 --> 00:18:39,677 So how are we going to determine the order for our reaction? 425 00:18:39,677 --> 00:18:41,510 And this is what are going to do on day one. 426 00:18:41,510 --> 00:18:44,180 We will use our rate law expression 427 00:18:44,180 --> 00:18:47,130 to determine the order of the reaction. 428 00:18:47,130 --> 00:18:48,530 So you're going to-- 429 00:18:48,530 --> 00:18:51,630 according to our rate law here. 430 00:18:51,630 --> 00:18:53,630 It's the only reactant that we have in this case 431 00:18:53,630 --> 00:18:55,100 is hydrogen peroxide, and we need 432 00:18:55,100 --> 00:18:56,990 to determine what its order is. 433 00:18:59,417 --> 00:19:01,500 So if we change the concentration of the peroxide, 434 00:19:01,500 --> 00:19:05,040 we should change the rate, yes? 435 00:19:05,040 --> 00:19:07,890 So if we do a bunch of reactions with a bunch 436 00:19:07,890 --> 00:19:10,200 of different concentrations of peroxide, 437 00:19:10,200 --> 00:19:12,135 we can measure the rates, and then 438 00:19:12,135 --> 00:19:14,010 use the relationship between those two things 439 00:19:14,010 --> 00:19:17,647 to figure out our concentration of-- 440 00:19:17,647 --> 00:19:18,855 or our order of the reaction. 441 00:19:22,993 --> 00:19:24,910 So the way that you're going to do this in lab 442 00:19:24,910 --> 00:19:27,430 is you will have a series of solutions, 443 00:19:27,430 --> 00:19:30,483 and these are your solutions. 444 00:19:30,483 --> 00:19:32,400 You'll have a stock hydrogen peroxide solution 445 00:19:32,400 --> 00:19:33,608 that you're going to make up. 446 00:19:33,608 --> 00:19:35,800 It's going to be about 4% hydrogen peroxide. 447 00:19:35,800 --> 00:19:37,050 You'll use a phosphate buffer. 448 00:19:37,050 --> 00:19:39,350 Why do we need to use a buffer for this reaction? 449 00:19:45,110 --> 00:19:48,200 What's a buffer, I guess is the first question? 450 00:19:48,200 --> 00:19:51,663 AUDIENCE: It helps the solution from changing PH2. 451 00:19:51,663 --> 00:19:52,580 SARAH HEWETT: Perfect. 452 00:19:52,580 --> 00:19:55,070 So a buffer helps the solution, it prevents a solution 453 00:19:55,070 --> 00:19:56,810 from changing PH. 454 00:19:56,810 --> 00:19:58,730 So you can make a buffer out of certain PH, 455 00:19:58,730 --> 00:20:00,480 and then if acid or base gets added to it, 456 00:20:00,480 --> 00:20:01,780 it resists the change in PH. 457 00:20:01,780 --> 00:20:02,840 It keeps the constant. 458 00:20:02,840 --> 00:20:06,040 Why is that important for our reaction? 459 00:20:06,040 --> 00:20:07,778 AUDIENCE: Maybe [INAUDIBLE]. 460 00:20:07,778 --> 00:20:08,570 SARAH HEWETT: Yeah. 461 00:20:08,570 --> 00:20:14,280 So enzymes are most functional at a set PH. 462 00:20:14,280 --> 00:20:16,050 So your PH of your body is around 7, 463 00:20:16,050 --> 00:20:19,327 so we want to keep the PH of our reaction 464 00:20:19,327 --> 00:20:20,910 somewhere around our physiological PH, 465 00:20:20,910 --> 00:20:24,270 so our buffer is going to be set to PH 6.8, which 466 00:20:24,270 --> 00:20:26,700 is going to help make sure that the enzyme is 467 00:20:26,700 --> 00:20:27,787 in its active state. 468 00:20:27,787 --> 00:20:28,620 It is not denatured. 469 00:20:28,620 --> 00:20:31,235 If you change the PH too much, you'll 470 00:20:31,235 --> 00:20:33,360 change the protonation state of the different parts 471 00:20:33,360 --> 00:20:35,885 of the protein, and it can fall apart. 472 00:20:35,885 --> 00:20:37,260 So we want to make sure that this 473 00:20:37,260 --> 00:20:39,480 is happening at the correct PH. 474 00:20:39,480 --> 00:20:41,520 We'll add some enzyme, and then we 475 00:20:41,520 --> 00:20:44,110 will measure the rate of the reaction. 476 00:20:44,110 --> 00:20:49,003 And we're going to do that using this apparatus right here. 477 00:20:49,003 --> 00:20:50,170 So you'll have one of these. 478 00:20:50,170 --> 00:20:51,420 You'll have a water bath, so that we can 479 00:20:51,420 --> 00:20:52,870 keep the temperature constant. 480 00:20:52,870 --> 00:20:54,510 So you'll just fill this with room temperature water, 481 00:20:54,510 --> 00:20:56,177 and then you can monitor the temperature 482 00:20:56,177 --> 00:20:59,590 throughout your reaction to make sure that it does not change. 483 00:20:59,590 --> 00:21:01,362 And then this is your reaction vessel 484 00:21:01,362 --> 00:21:03,570 here, your pressure tube, because you will be putting 485 00:21:03,570 --> 00:21:04,820 all of your solutions in here. 486 00:21:04,820 --> 00:21:08,220 You will add your peroxide and your buffer, 487 00:21:08,220 --> 00:21:09,930 and then you will put this cap on. 488 00:21:09,930 --> 00:21:13,800 And this Teflon cap here, it's important to note, 489 00:21:13,800 --> 00:21:17,213 has an O-ring on the bottom. 490 00:21:17,213 --> 00:21:18,880 And so you want to make sure when you're 491 00:21:18,880 --> 00:21:20,260 doing this reaction that you're O-ring 492 00:21:20,260 --> 00:21:22,000 is in there, because that'll make a good seal, 493 00:21:22,000 --> 00:21:23,770 so you won't have your products escaping 494 00:21:23,770 --> 00:21:26,630 because our product is a gas. 495 00:21:26,630 --> 00:21:27,760 So you'll screw this on. 496 00:21:27,760 --> 00:21:30,095 And then there's a hole in the top here. 497 00:21:30,095 --> 00:21:31,720 You can inject your enzyme really fast. 498 00:21:31,720 --> 00:21:32,710 You're going be doing this in partners. 499 00:21:32,710 --> 00:21:33,970 Somebody can inject the enzyme really fast. 500 00:21:33,970 --> 00:21:36,250 And then you want to connect your pressure tube. 501 00:21:36,250 --> 00:21:38,460 And this tube is connected to a pressure sensor. 502 00:21:38,460 --> 00:21:40,210 And this pressure sensor will be connected 503 00:21:40,210 --> 00:21:42,210 to your computer, which is why you need to bring 504 00:21:42,210 --> 00:21:44,200 a laptop for the catalase lab. 505 00:21:44,200 --> 00:21:47,380 And we will give you the Logger Pro software. 506 00:21:47,380 --> 00:21:49,507 And it will send the data directly to your laptop. 507 00:21:49,507 --> 00:21:50,590 And it'll plot it for you. 508 00:21:50,590 --> 00:21:51,610 And you'll get a curve that, hopefully, 509 00:21:51,610 --> 00:21:52,960 looks something like this. 510 00:21:52,960 --> 00:21:59,170 And we will measure the pressure of oxygen formed in kilopascals 511 00:21:59,170 --> 00:22:01,360 versus time in seconds. 512 00:22:01,360 --> 00:22:03,640 And it'll graph this thing for you. 513 00:22:03,640 --> 00:22:05,740 And the slope of the graph is going 514 00:22:05,740 --> 00:22:10,290 to be your rate of kilopascals per second. 515 00:22:10,290 --> 00:22:12,790 And we want to take the rate at this first part of the graph 516 00:22:12,790 --> 00:22:14,710 where it is linear, and why do we 517 00:22:14,710 --> 00:22:18,010 want to take the rate at the beginning of our reaction? 518 00:22:21,080 --> 00:22:21,580 Yes. 519 00:22:21,580 --> 00:22:23,730 AUDIENCE: Reaction rate is dependent on amount 520 00:22:23,730 --> 00:22:24,918 of reactants? 521 00:22:24,918 --> 00:22:25,710 SARAH HEWETT: Yeah. 522 00:22:25,710 --> 00:22:27,668 So the reaction rate is dependent on the amount 523 00:22:27,668 --> 00:22:29,910 of reactants, and the-- 524 00:22:29,910 --> 00:22:33,270 so the rate of this reaction obviously changes over time, 525 00:22:33,270 --> 00:22:37,350 and we set up our reactions so that we know 526 00:22:37,350 --> 00:22:38,940 the concentration of peroxide. 527 00:22:38,940 --> 00:22:40,417 And the only time in this reaction 528 00:22:40,417 --> 00:22:42,000 that we're theoretically going to know 529 00:22:42,000 --> 00:22:44,010 the concentration of peroxide is at the beginning, 530 00:22:44,010 --> 00:22:46,140 before some of it has reacted and the rate changes. 531 00:22:46,140 --> 00:22:48,660 So we want to measure the initial rate so 532 00:22:48,660 --> 00:22:52,260 that we know our concentration, and that we get a-- 533 00:22:52,260 --> 00:22:54,090 we have a consistent place to take our data 534 00:22:54,090 --> 00:22:57,830 from on each measurement. 535 00:22:57,830 --> 00:23:02,720 So once we have done all of these different reactions-- 536 00:23:02,720 --> 00:23:05,030 you'll do all four of them-- all of the same procedure 537 00:23:05,030 --> 00:23:08,090 in the same tube-- you'll make five different graphs. 538 00:23:08,090 --> 00:23:08,990 You'll have this. 539 00:23:08,990 --> 00:23:11,960 Then how do we analyze this data and get information 540 00:23:11,960 --> 00:23:14,520 about the order out of it? 541 00:23:14,520 --> 00:23:17,120 So here we are going to have to do a little bit of math. 542 00:23:20,460 --> 00:23:22,890 So here are some of the steps of the data analysis. 543 00:23:22,890 --> 00:23:23,660 The first thing that you're going to have to do 544 00:23:23,660 --> 00:23:26,690 is calculate the concentration of the peroxide that you used. 545 00:23:26,690 --> 00:23:37,730 And we are going to give you 30% hydrogen peroxide, which is-- 546 00:23:37,730 --> 00:23:43,610 its volume per volume-- so there's 30 milliliters of H2O2, 547 00:23:43,610 --> 00:23:45,140 and 70 millimeters of water. 548 00:23:47,763 --> 00:23:49,430 So if you remember that your molarity is 549 00:23:49,430 --> 00:23:53,660 your moles of your solute over the total volume 550 00:23:53,660 --> 00:23:57,580 of the solution, you can turn this milliliters, assuming 551 00:23:57,580 --> 00:24:00,460 a density of about 1, into grams, grams to moles, 552 00:24:00,460 --> 00:24:03,040 and you can calculate the molarity of this solution. 553 00:24:03,040 --> 00:24:06,070 You're then going to take this 30% hydrogen peroxide that we 554 00:24:06,070 --> 00:24:13,580 give you, and dilute it 13.3 milliliters to 100 milliliters. 555 00:24:13,580 --> 00:24:15,470 So then you can do another dilution equation 556 00:24:15,470 --> 00:24:17,762 to figure out your final concentration of your hydrogen 557 00:24:17,762 --> 00:24:21,060 peroxide that you're going to be using in the lab. 558 00:24:21,060 --> 00:24:22,395 So that's a first step. 559 00:24:22,395 --> 00:24:24,020 And then I'm going to kind of rearrange 560 00:24:24,020 --> 00:24:25,478 a couple of these other steps, just 561 00:24:25,478 --> 00:24:28,840 because it'll make this a little bit easier to go through. 562 00:24:28,840 --> 00:24:30,590 But the first thing that we're going to do 563 00:24:30,590 --> 00:24:34,370 is the easy part, which is get your rate of oxygen formation 564 00:24:34,370 --> 00:24:36,040 in kilopascals per second. 565 00:24:36,040 --> 00:24:37,790 And that we're just going to read straight 566 00:24:37,790 --> 00:24:38,957 from the slope of the graph. 567 00:24:38,957 --> 00:24:39,980 So that's pretty easy. 568 00:24:39,980 --> 00:24:44,420 So we'll have our rate of oxygen formation 569 00:24:44,420 --> 00:24:48,840 in kilopascals per second. 570 00:24:48,840 --> 00:24:49,710 Great. 571 00:24:49,710 --> 00:24:56,350 So now we want to take a look at our rate law. 572 00:24:56,350 --> 00:24:58,240 And we have our rate of oxygen formation, 573 00:24:58,240 --> 00:25:00,510 but what's in our rate law? 574 00:25:00,510 --> 00:25:02,020 Hydrogen peroxide. 575 00:25:02,020 --> 00:25:05,010 So we need to find a way to go from oxygen and kilopascals 576 00:25:05,010 --> 00:25:10,020 per second to moles per liter per second of hydrogen 577 00:25:10,020 --> 00:25:11,307 peroxide. 578 00:25:11,307 --> 00:25:13,140 So the first way that we're going to do that 579 00:25:13,140 --> 00:25:16,560 is to go from kilopascals per second here to molarity 580 00:25:16,560 --> 00:25:23,170 of oxygen. And we can do that using our gas constant here. 581 00:25:23,170 --> 00:25:25,710 So if you divide by the gas constant, 582 00:25:25,710 --> 00:25:36,330 multiply by 1 over 8.314 moles, liters times kilopascals, 583 00:25:36,330 --> 00:25:38,203 we can cancel out our kilopascals. 584 00:25:38,203 --> 00:25:40,120 And we'll have moles per liter, which is good, 585 00:25:40,120 --> 00:25:41,460 but then we still have this K, which 586 00:25:41,460 --> 00:25:43,127 is our temperature in Kelvin, so we also 587 00:25:43,127 --> 00:25:46,320 have to divide by our temperature in Kelvin. 588 00:25:48,890 --> 00:25:53,300 And this will get us our rate of oxygen 589 00:25:53,300 --> 00:25:59,300 in moles per liter per second, which is pretty good. 590 00:25:59,300 --> 00:26:00,320 We're close. 591 00:26:00,320 --> 00:26:04,117 But we still need to get from oxygen to hydrogen peroxide. 592 00:26:04,117 --> 00:26:06,200 So how can we get from oxygen to hydrogen peroxide 593 00:26:06,200 --> 00:26:09,112 using this information? 594 00:26:09,112 --> 00:26:11,380 AUDIENCE: [INAUDIBLE] 595 00:26:11,380 --> 00:26:12,630 SARAH HEWETT: It would be-- 596 00:26:12,630 --> 00:26:14,345 so the ratio is 2:1, right. 597 00:26:14,345 --> 00:26:15,720 So there's two hydrogen peroxides 598 00:26:15,720 --> 00:26:17,610 in this reaction for every one oxygen. 599 00:26:17,610 --> 00:26:21,460 But these coefficients are in moles. 600 00:26:21,460 --> 00:26:23,555 And this is in moles per liter. 601 00:26:23,555 --> 00:26:25,930 So we need to figure out how many moles of oxygen we have 602 00:26:25,930 --> 00:26:29,453 before we can use our stoichiometry ratio here. 603 00:26:29,453 --> 00:26:31,870 So how are we going to figure out how many moles of oxygen 604 00:26:31,870 --> 00:26:32,370 we have? 605 00:26:32,370 --> 00:26:34,570 We need to know what our volume of oxygen was. 606 00:26:34,570 --> 00:26:37,668 And for that we can go to our pressure tube. 607 00:26:37,668 --> 00:26:40,210 So you'll have some of this is going to be your solution down 608 00:26:40,210 --> 00:26:42,130 here, so that'll be liquid. 609 00:26:42,130 --> 00:26:44,380 And then we need to calculate the volume of the gas 610 00:26:44,380 --> 00:26:45,942 above our reaction, which is where 611 00:26:45,942 --> 00:26:47,150 oxygen is going to be formed. 612 00:26:47,150 --> 00:26:50,230 So we'll need to know the volume of this, 613 00:26:50,230 --> 00:26:51,970 and the volume of the pressure tube. 614 00:26:51,970 --> 00:26:53,650 And the volume of the pressure tube has already been measured, 615 00:26:53,650 --> 00:26:54,460 and we'll give that to you. 616 00:26:54,460 --> 00:26:55,870 And you guys are going to measure 617 00:26:55,870 --> 00:26:59,208 in the lab what the volume of your reaction vessel is. 618 00:26:59,208 --> 00:27:01,000 You're going to fill this thing with water, 619 00:27:01,000 --> 00:27:02,590 weigh it, then weigh it empty, and then you 620 00:27:02,590 --> 00:27:04,715 can calculate by difference in the density of water 621 00:27:04,715 --> 00:27:08,000 what your volume of your whole tube is. 622 00:27:08,000 --> 00:27:10,520 And then you know your reaction volume is 25 milliliters, 623 00:27:10,520 --> 00:27:14,570 so you can subtract those and get the volume of the gas. 624 00:27:14,570 --> 00:27:16,640 So if we know these two together, 625 00:27:16,640 --> 00:27:20,500 you'll get the volume of the gas above your reaction. 626 00:27:23,220 --> 00:27:28,970 So if we have our rate of oxygen formation in moles per liter 627 00:27:28,970 --> 00:27:32,990 per second, we can multiply that by our volume 628 00:27:32,990 --> 00:27:36,850 that we calculate, so liters of oxygen. 629 00:27:36,850 --> 00:27:46,040 And then we have our rate in moles of oxygen per second. 630 00:27:46,040 --> 00:27:48,670 And now we can use our stoichiometry, 631 00:27:48,670 --> 00:27:54,610 because we have it in moles, so we can take our rate in moles 632 00:27:54,610 --> 00:28:01,090 per second, and then we know that it is 1 mole of oxygen 633 00:28:01,090 --> 00:28:05,020 for 2 moles H2O2. 634 00:28:05,020 --> 00:28:12,817 Then we get our rate H2O2 in moles per second. 635 00:28:12,817 --> 00:28:14,650 And what are the units of rate that we want? 636 00:28:19,430 --> 00:28:21,703 Moles per liter per second. 637 00:28:21,703 --> 00:28:23,120 So we have it in miles per second. 638 00:28:23,120 --> 00:28:23,750 We're so close. 639 00:28:23,750 --> 00:28:26,630 Then we just need to divide by the liters of our reaction, 640 00:28:26,630 --> 00:28:31,040 which if you go back a couple of slides, is 25 milliliters, 641 00:28:31,040 --> 00:28:35,040 so all of our reaction volumes are 25 milliliters. 642 00:28:35,040 --> 00:28:37,340 So if you convert that to liters, divide by 0.25 643 00:28:37,340 --> 00:28:43,600 liters, and then we will have our rate 644 00:28:43,600 --> 00:28:47,110 in moles per liter per second, which is what we want. 645 00:28:50,600 --> 00:28:52,540 Now this still doesn't get us to a, 646 00:28:52,540 --> 00:28:56,470 but we can rearrange this equation 647 00:28:56,470 --> 00:28:58,220 by taking the natural log of both sides. 648 00:28:58,220 --> 00:29:01,930 So if you have the natural log of the rate 649 00:29:01,930 --> 00:29:08,020 equals the natural log of K plus, 650 00:29:08,020 --> 00:29:11,200 then the A comes down, a times the natural log 651 00:29:11,200 --> 00:29:16,750 of your hydrogen peroxide concentration, then-- 652 00:29:16,750 --> 00:29:20,320 we've just figured this out from all of that math. 653 00:29:20,320 --> 00:29:22,600 We know this concentration. 654 00:29:22,600 --> 00:29:24,440 And this is going to be our y-intercept. 655 00:29:24,440 --> 00:29:29,100 So if we have y equals b plus mx, 656 00:29:29,100 --> 00:29:31,260 if we make a graph of the hydrogen-- 657 00:29:31,260 --> 00:29:33,570 or the natural log of the peroxide concentration 658 00:29:33,570 --> 00:29:35,850 and the natural log of the rate, then our slope 659 00:29:35,850 --> 00:29:38,520 is going to be our order. 660 00:29:38,520 --> 00:29:40,695 Hopefully, we haven't lost you. 661 00:29:40,695 --> 00:29:43,320 So the way that you're going to treat all this data is you can, 662 00:29:43,320 --> 00:29:44,820 instead of having to do this calculation out 663 00:29:44,820 --> 00:29:47,195 for every single trial, you can make a giant spreadsheet. 664 00:29:47,195 --> 00:29:49,802 And in the lab manual, it tells you what data 665 00:29:49,802 --> 00:29:50,760 we want you to collect. 666 00:29:50,760 --> 00:29:53,173 And this is all of it here. 667 00:29:53,173 --> 00:29:54,840 And then you can make a spreadsheet that 668 00:29:54,840 --> 00:29:57,000 does all of the calculations for you, that gets you down 669 00:29:57,000 --> 00:29:58,500 to the natural log of rate, and the natural log 670 00:29:58,500 --> 00:29:59,660 of hydrogen peroxide. 671 00:29:59,660 --> 00:30:01,830 So this is an example of a pretty good way 672 00:30:01,830 --> 00:30:03,060 to present your data. 673 00:30:03,060 --> 00:30:05,643 And I know it's kind of hard to see on the printed out slides, 674 00:30:05,643 --> 00:30:09,757 but these will be on Stellar if you want to look at them. 675 00:30:09,757 --> 00:30:11,840 And then your graph will look something like this. 676 00:30:11,840 --> 00:30:12,770 And you'll have a straight line. 677 00:30:12,770 --> 00:30:14,228 And so from that straight line, you 678 00:30:14,228 --> 00:30:17,710 can figure out what your order of your reaction 679 00:30:17,710 --> 00:30:18,930 is based on your slope. 680 00:30:22,730 --> 00:30:25,670 So that was a lot. 681 00:30:25,670 --> 00:30:27,457 So once we have that done on day one, 682 00:30:27,457 --> 00:30:29,540 then, if you remember our second goal for the lab, 683 00:30:29,540 --> 00:30:30,998 it was to figure out the activation 684 00:30:30,998 --> 00:30:32,660 energy of the reaction. 685 00:30:34,958 --> 00:30:36,500 And so the way that we're going to do 686 00:30:36,500 --> 00:30:38,085 that is to use the Arrhenius equation, 687 00:30:38,085 --> 00:30:39,710 and that says that the rate constant is 688 00:30:39,710 --> 00:30:44,420 equal to A, which is this collision frequency factor, 689 00:30:44,420 --> 00:30:48,650 times e to the negative activation energy over RT. 690 00:30:48,650 --> 00:30:50,998 And if we remember the things that can change the rate, 691 00:30:50,998 --> 00:30:52,790 we can change the concentration and that'll 692 00:30:52,790 --> 00:30:55,050 affect the rate, and also the temperature. 693 00:30:55,050 --> 00:30:58,190 So if we do our reaction at different temperatures, 694 00:30:58,190 --> 00:31:00,023 then we can determine our activation energy. 695 00:31:00,023 --> 00:31:01,523 So what you're going to do is you're 696 00:31:01,523 --> 00:31:03,398 going to pick one of the trials from day one. 697 00:31:03,398 --> 00:31:05,731 Usually people pick the middle one because this is easy. 698 00:31:05,731 --> 00:31:07,595 It's just 1 milliliter, no decimals. 699 00:31:07,595 --> 00:31:10,370 Just easy to measure and it's right in the middle. 700 00:31:10,370 --> 00:31:12,990 You'll pick one and you'll hold the concentration of peroxide 701 00:31:12,990 --> 00:31:14,990 constant, and then we will vary the temperature. 702 00:31:14,990 --> 00:31:18,080 So you'll do seven runs at varying temperatures. 703 00:31:18,080 --> 00:31:20,480 So you'll pick a temperature in each of these ranges 704 00:31:20,480 --> 00:31:22,190 and you will measure the rate. 705 00:31:22,190 --> 00:31:24,920 Again, you'll get the same graph, the measure 706 00:31:24,920 --> 00:31:28,010 the rate of oxygen per second. 707 00:31:28,010 --> 00:31:33,640 And then you can do all of this same math 708 00:31:33,640 --> 00:31:36,250 to get your information in concentration of peroxide 709 00:31:36,250 --> 00:31:38,125 to go from oxygen to peroxide, because that's 710 00:31:38,125 --> 00:31:39,530 what we care about. 711 00:31:39,530 --> 00:31:41,090 The keys to success for this reaction 712 00:31:41,090 --> 00:31:43,490 are to wait for the peroxide and the buffer 713 00:31:43,490 --> 00:31:46,170 to reach the correct temperature before you add the enzyme. 714 00:31:46,170 --> 00:31:50,222 So when you have your reaction here in this tube, 715 00:31:50,222 --> 00:31:51,930 you'll put it in your water bath and then 716 00:31:51,930 --> 00:31:53,305 you want to give it a few minutes 717 00:31:53,305 --> 00:31:57,182 to stir and come to equilibrium at the right temperature, 718 00:31:57,182 --> 00:31:58,890 because it'll all be at room temperature. 719 00:31:58,890 --> 00:32:01,515 And then if you're trying to do your reaction at 0 degrees or 5 720 00:32:01,515 --> 00:32:06,255 degrees, your reaction part won't actually be at 5 degrees 721 00:32:06,255 --> 00:32:07,380 even if your water bath is. 722 00:32:07,380 --> 00:32:09,960 So give it a few minutes to equilibrate 723 00:32:09,960 --> 00:32:11,610 before you take your measurements 724 00:32:11,610 --> 00:32:14,603 and before you inject your enzyme. 725 00:32:14,603 --> 00:32:16,020 Another key to success is to start 726 00:32:16,020 --> 00:32:18,000 at the hottest temperature and then add ice to cool it. 727 00:32:18,000 --> 00:32:19,710 It's easier to control the cooling 728 00:32:19,710 --> 00:32:21,510 than it is to control the heating with these hot plates. 729 00:32:21,510 --> 00:32:22,890 The hot plates tend to get really excited 730 00:32:22,890 --> 00:32:24,150 and then they'll heat your solution up 731 00:32:24,150 --> 00:32:26,790 way above what it needs to, and then it won't be able to cool. 732 00:32:26,790 --> 00:32:29,332 So if you start at your hottest temperature and then add ice, 733 00:32:29,332 --> 00:32:31,320 you'll be able to slowly lower the temperature 734 00:32:31,320 --> 00:32:34,030 and do it in a more controlled fashion. 735 00:32:34,030 --> 00:32:35,970 The other important thing about this reaction 736 00:32:35,970 --> 00:32:38,760 for day one and two, and I'm sure your TAs will emphasize 737 00:32:38,760 --> 00:32:41,135 this when they tell you in lab and you guys have a chance 738 00:32:41,135 --> 00:32:44,180 to have this in front of you, is to do everything really 739 00:32:44,180 --> 00:32:44,680 quickly. 740 00:32:44,680 --> 00:32:46,470 So the reaction starts as soon as you add the enzyme. 741 00:32:46,470 --> 00:32:47,845 So you'll have your micropipette, 742 00:32:47,845 --> 00:32:49,303 you'll stick it right in that hole, 743 00:32:49,303 --> 00:32:50,880 add the enzyme really fast, and then 744 00:32:50,880 --> 00:32:54,147 you want to attach your pressure tube 745 00:32:54,147 --> 00:32:56,730 and then hit go on your computer to start collecting the data. 746 00:32:56,730 --> 00:32:58,992 And that all has to happen in like, a second so 747 00:32:58,992 --> 00:33:00,950 that you don't miss that beginning of your data 748 00:33:00,950 --> 00:33:04,200 collection. 749 00:33:04,200 --> 00:33:08,040 So those are some important things. 750 00:33:08,040 --> 00:33:10,277 If we talk about the data analysis for this reaction, 751 00:33:10,277 --> 00:33:11,860 it's kind of similar to the other one. 752 00:33:11,860 --> 00:33:13,530 So you'll calculate the concentration of peroxide, 753 00:33:13,530 --> 00:33:15,760 you'll calculate the volume of air above your reaction. 754 00:33:15,760 --> 00:33:17,760 You'll have the initial rate of oxygen formation 755 00:33:17,760 --> 00:33:19,240 in kilopascals per second. 756 00:33:19,240 --> 00:33:21,780 Then you can get the initial rate of oxygen formation 757 00:33:21,780 --> 00:33:25,380 in molarity per second and moles per second. 758 00:33:25,380 --> 00:33:29,520 Then you can change your rate of oxygen formation 759 00:33:29,520 --> 00:33:33,272 to the rate of peroxide decomposition, same math. 760 00:33:33,272 --> 00:33:35,730 And then using the rate law that you determined on day one, 761 00:33:35,730 --> 00:33:37,563 you're going to calculate the rate constant. 762 00:33:37,563 --> 00:33:42,270 So if we have our rate, our general rate law, 763 00:33:42,270 --> 00:33:45,360 we'll measure this in the lab or we'll calculate this, I guess. 764 00:33:50,160 --> 00:33:51,750 We will know this from day one. 765 00:33:58,520 --> 00:34:00,020 So you'll plug in the value that you 766 00:34:00,020 --> 00:34:02,702 get from your first set of calculations right there. 767 00:34:02,702 --> 00:34:04,160 And then we measure this in the lab 768 00:34:04,160 --> 00:34:06,170 or we can calculate/measure this. 769 00:34:11,400 --> 00:34:14,190 So we can calculate our rate constant, 770 00:34:14,190 --> 00:34:17,405 which is, if you just rearrange this, it'll be k-- 771 00:34:25,900 --> 00:34:27,639 so that's not so bad. 772 00:34:27,639 --> 00:34:31,630 And then in order to get our activation energy out of this, 773 00:34:31,630 --> 00:34:34,795 we are again going to take the natural log of both sides. 774 00:34:52,960 --> 00:34:55,503 I think that I did that out correctly. 775 00:35:00,396 --> 00:35:02,350 No plus sign here. 776 00:35:02,350 --> 00:35:06,290 All right, so this is your linear form of this equation. 777 00:35:06,290 --> 00:35:12,495 So we have, again, y equals b m and x. 778 00:35:12,495 --> 00:35:14,620 So if we do our reaction at different temperatures, 779 00:35:14,620 --> 00:35:18,160 then we will know the temperature of our reaction. 780 00:35:18,160 --> 00:35:21,310 And then we will get k from our rate constant from our rate 781 00:35:21,310 --> 00:35:24,040 law, and you'll calculate that for each of your trials, 782 00:35:24,040 --> 00:35:26,050 as well, based on the rate. 783 00:35:26,050 --> 00:35:28,840 And then our slope is going to be the activation energy 784 00:35:28,840 --> 00:35:30,290 over the ideal gas constant. 785 00:35:30,290 --> 00:35:31,750 So we can get the activation energy 786 00:35:31,750 --> 00:35:35,320 from the slope of a graph of 1 over t 787 00:35:35,320 --> 00:35:38,093 times the natural log of k versus the natural log of k. 788 00:35:38,093 --> 00:35:40,510 And then you can also get your collision frequency factor, 789 00:35:40,510 --> 00:35:42,440 this A term, from your y-intercept, 790 00:35:42,440 --> 00:35:45,693 so you'll also be able to determine that. 791 00:35:45,693 --> 00:35:47,110 Then you'll use your Linus program 792 00:35:47,110 --> 00:35:49,010 to get the errors in all of these things, 793 00:35:49,010 --> 00:35:53,050 and that is essentially day one and day two of the lab. 794 00:35:53,050 --> 00:35:56,340 Do you guys have any questions about that? 795 00:35:59,830 --> 00:36:01,060 There's a lot of math. 796 00:36:01,060 --> 00:36:03,040 So again, there's another data chart 797 00:36:03,040 --> 00:36:04,927 that you can make for day two of the lab that 798 00:36:04,927 --> 00:36:06,760 has all of the information that you're going 799 00:36:06,760 --> 00:36:08,890 to need for these calculations. 800 00:36:08,890 --> 00:36:14,080 And then this is hopefully what your graph will look like. 801 00:36:14,080 --> 00:36:17,050 It should be linear with a negative slope, 802 00:36:17,050 --> 00:36:18,550 and then the negative will get taken 803 00:36:18,550 --> 00:36:21,832 care of with that negative sign in the equation. 804 00:36:21,832 --> 00:36:23,540 AUDIENCE: This will be posted on Stellar? 805 00:36:23,540 --> 00:36:24,698 SARAH HEWETT: Yes. 806 00:36:24,698 --> 00:36:26,740 Yeah, all of the slides will be posted on Stellar 807 00:36:26,740 --> 00:36:28,600 so you can see it in a larger form, 808 00:36:28,600 --> 00:36:32,335 because I know they didn't print out super well. 809 00:36:32,335 --> 00:36:32,835 OK. 810 00:36:38,320 --> 00:36:42,540 So now we can take a look at the reaction 811 00:36:42,540 --> 00:36:46,840 that you're going to do in a slightly different form. 812 00:36:46,840 --> 00:36:49,570 And you may have seen this before, 813 00:36:49,570 --> 00:36:51,800 but we're going to do it anyway. 814 00:36:51,800 --> 00:36:58,390 So hydrogen peroxide, you may have some at your house. 815 00:36:58,390 --> 00:37:00,100 They sell it in a drugstore. 816 00:37:00,100 --> 00:37:02,350 It's like, 3% so it's not as concentrated as the stuff 817 00:37:02,350 --> 00:37:04,017 that we're going to be using in the lab. 818 00:37:04,017 --> 00:37:05,480 But nonetheless, hydrogen peroxide 819 00:37:05,480 --> 00:37:07,990 is a thing that you can buy. 820 00:37:07,990 --> 00:37:12,058 And it naturally decomposes over time, 821 00:37:12,058 --> 00:37:13,600 so this reaction is always happening. 822 00:37:13,600 --> 00:37:15,350 If you have a bottle of hydrogen peroxide, 823 00:37:15,350 --> 00:37:17,540 usually the caps are vented because if you seal it 824 00:37:17,540 --> 00:37:19,540 for too long, you'll build up pressure of oxygen 825 00:37:19,540 --> 00:37:20,692 and that's a problem. 826 00:37:20,692 --> 00:37:22,400 The stuff that we have in the lab is 30%, 827 00:37:22,400 --> 00:37:25,120 so that's definitely vented, and we store it in the refrigerator 828 00:37:25,120 --> 00:37:28,000 so that we slow down the reaction 829 00:37:28,000 --> 00:37:31,150 and keep our product for longer. 830 00:37:31,150 --> 00:37:34,420 So it is always happening and you can speed it up 831 00:37:34,420 --> 00:37:35,370 in a number of ways. 832 00:37:35,370 --> 00:37:37,840 So one of the ways is obviously using enzymes, catalase. 833 00:37:37,840 --> 00:37:39,867 That'll speed up the reaction. 834 00:37:39,867 --> 00:37:42,200 But there are other catalysts that you can use, as well. 835 00:37:42,200 --> 00:37:46,000 So have you guys seen the elephant toothpaste reaction 836 00:37:46,000 --> 00:37:47,290 before? 837 00:37:47,290 --> 00:37:48,190 Yes. 838 00:37:48,190 --> 00:37:49,607 Do you guys know what the catalyst 839 00:37:49,607 --> 00:37:50,620 is that we use for this? 840 00:37:50,620 --> 00:37:55,390 There's a few you can use, but does anyone remember? 841 00:37:55,390 --> 00:38:01,600 So we're going to react hydrogen peroxide with potassium 842 00:38:01,600 --> 00:38:02,570 iodide in this case. 843 00:38:02,570 --> 00:38:03,670 And you can use a couple different ones, 844 00:38:03,670 --> 00:38:05,378 like manganese dioxide, I believe, works. 845 00:38:05,378 --> 00:38:06,910 You can use different iodide salts, 846 00:38:06,910 --> 00:38:11,570 but potassium iodide is the one that I have today. 847 00:38:11,570 --> 00:38:13,850 And we're going to do a little bit of an experiment. 848 00:38:13,850 --> 00:38:17,800 So we said that concentration effects rate, right? 849 00:38:17,800 --> 00:38:19,720 So we will try our first reaction 850 00:38:19,720 --> 00:38:22,870 with some hydrogen peroxide. 851 00:38:22,870 --> 00:38:31,460 And I'm going to pour out about 10 milliliters of this 852 00:38:31,460 --> 00:38:35,360 and then dilute it so that our new concentration is about 7%. 853 00:38:44,400 --> 00:38:47,010 Yeah, that's right. 854 00:38:47,010 --> 00:38:49,240 So pour that in there. 855 00:38:49,240 --> 00:38:53,330 And then we want to use a potassium iodide solution. 856 00:38:59,300 --> 00:39:03,700 So we can pour some of this in here. 857 00:39:03,700 --> 00:39:05,830 And then we have the oxygen bubbles, 858 00:39:05,830 --> 00:39:08,650 and who did the catalase reaction yesterday in lab? 859 00:39:08,650 --> 00:39:10,300 Anybody who's here? 860 00:39:10,300 --> 00:39:12,760 So what did you guys see when you added the enzyme 861 00:39:12,760 --> 00:39:14,770 to your peroxide in the tube? 862 00:39:14,770 --> 00:39:17,170 Bubbles, good. 863 00:39:17,170 --> 00:39:18,490 But it didn't foam up, right? 864 00:39:18,490 --> 00:39:21,040 Because they just popped and formed oxygen. 865 00:39:21,040 --> 00:39:26,570 So the way that we can get this to foam is by adding some soap. 866 00:39:26,570 --> 00:39:29,390 This is just powdered soap. 867 00:39:29,390 --> 00:39:31,140 And we can add a couple of scoops of that. 868 00:39:33,900 --> 00:39:36,090 And now hopefully, if all goes well, 869 00:39:36,090 --> 00:39:39,060 when I add these together, we will see the decomposition 870 00:39:39,060 --> 00:39:40,489 of hydrogen peroxide. 871 00:39:50,016 --> 00:39:52,433 I can probably hold it up so you can see what's happening. 872 00:39:55,822 --> 00:39:57,030 So what's happening in there? 873 00:40:00,096 --> 00:40:01,830 It's bubbling, good. 874 00:40:01,830 --> 00:40:02,330 Excellent. 875 00:40:02,330 --> 00:40:03,960 So what are the bubbles? 876 00:40:03,960 --> 00:40:07,230 Oxygen. All right, so it's taking its time. 877 00:40:09,860 --> 00:40:12,460 So while that is going, we can set up another one. 878 00:40:15,072 --> 00:40:17,280 And this time, we won't dilute the hydrogen peroxide, 879 00:40:17,280 --> 00:40:25,960 so we'll just use 40 milliliters of hydrogen peroxide. 880 00:40:30,415 --> 00:40:31,140 Need our soap. 881 00:40:43,400 --> 00:40:44,360 Yeah. 882 00:40:44,360 --> 00:40:48,827 Yeah, so it looks like toothpaste maybe. 883 00:40:48,827 --> 00:40:50,660 Toothpaste that an elephant would use, yeah. 884 00:40:53,690 --> 00:40:54,680 What? 885 00:40:54,680 --> 00:40:56,090 Elephant toothpaste. 886 00:40:56,090 --> 00:40:57,050 Yeah. 887 00:40:57,050 --> 00:40:59,742 I also, in the course of doing some research for this, 888 00:40:59,742 --> 00:41:02,075 found that some people call it old foamy, like a guyser. 889 00:41:06,510 --> 00:41:08,130 So you may have heard it by that name. 890 00:41:10,720 --> 00:41:12,600 All right, and then we add the same amount 891 00:41:12,600 --> 00:41:13,960 of potassium iodide. 892 00:41:13,960 --> 00:41:15,585 Hopefully I measured this out properly. 893 00:41:18,180 --> 00:41:20,310 So if that was 7% hydrogen peroxide, 894 00:41:20,310 --> 00:41:22,393 what do we think is going to happen if we use 30%? 895 00:41:24,390 --> 00:41:26,140 Faster. 896 00:41:26,140 --> 00:41:27,050 Let's find out. 897 00:41:41,130 --> 00:41:43,410 So can you see the steam coming off of it? 898 00:41:43,410 --> 00:41:46,040 Yeah, so what does that mean about the reaction? 899 00:41:46,040 --> 00:41:46,957 It's exothermic. 900 00:41:46,957 --> 00:41:47,790 Yeah, it's very hot. 901 00:41:47,790 --> 00:41:51,840 If you were to come up here and touch this, it is quite warm. 902 00:41:51,840 --> 00:41:54,480 But yeah, so that went faster, right? 903 00:41:54,480 --> 00:41:56,640 So we can do a little bit of math 904 00:41:56,640 --> 00:42:00,720 about how much faster the potassium iodide makes 905 00:42:00,720 --> 00:42:03,570 the reaction go than just what would happen in your bottle 906 00:42:03,570 --> 00:42:05,100 at home. 907 00:42:05,100 --> 00:42:08,730 And so our activation energy of hydrogen peroxide decomposition 908 00:42:08,730 --> 00:42:10,620 that is uncatalyzed, just happens in nature, 909 00:42:10,620 --> 00:42:14,380 is 75 kilojoules per mole. 910 00:42:14,380 --> 00:42:16,170 So if we use our Arrhenius equation, 911 00:42:16,170 --> 00:42:19,320 then we can plug in 75 kilojoules or 75,000 joules 912 00:42:19,320 --> 00:42:22,980 to match our or gas constant units. 913 00:42:22,980 --> 00:42:25,350 And then the activation energy of the decomposition 914 00:42:25,350 --> 00:42:27,510 as catalyzed by potassium iodide is 915 00:42:27,510 --> 00:42:30,060 about 56 kilojoules per mole, so it lowers it, 916 00:42:30,060 --> 00:42:32,840 makes the reaction go faster. 917 00:42:32,840 --> 00:42:36,020 If you do this math out-- 918 00:42:36,020 --> 00:42:38,150 I don't want to get my numbers wrong here-- 919 00:42:38,150 --> 00:42:49,580 it is about 2,500 times faster or 2,400 times faster 920 00:42:49,580 --> 00:42:51,320 than what would happen in nature. 921 00:42:53,870 --> 00:42:57,370 Now, if we talk about catalase, and you guys 922 00:42:57,370 --> 00:42:59,770 will calculate the actual activation 923 00:42:59,770 --> 00:43:02,830 energy of the catalase-catalyzed reaction, 924 00:43:02,830 --> 00:43:05,860 I will start and tell you that it is less than 10 kilojoules 925 00:43:05,860 --> 00:43:06,373 per mole. 926 00:43:06,373 --> 00:43:08,290 So that is a pretty significant change, right? 927 00:43:08,290 --> 00:43:12,830 Going from 75 kilojoules per mole down to 10 or less. 928 00:43:12,830 --> 00:43:13,460 That's a lot. 929 00:43:13,460 --> 00:43:16,820 So if you do this math out, where you go from 75,000 joules 930 00:43:16,820 --> 00:43:20,000 to 10,000 joules, does anyone have any guesses 931 00:43:20,000 --> 00:43:21,980 as to how much faster the catalase is 932 00:43:21,980 --> 00:43:25,700 than just normal decomposition? 933 00:43:25,700 --> 00:43:26,300 A lot. 934 00:43:37,670 --> 00:43:38,710 So that's a lot faster. 935 00:43:42,195 --> 00:43:43,570 So you can be thinking about that 936 00:43:43,570 --> 00:43:45,237 when you are thinking about what happens 937 00:43:45,237 --> 00:43:49,060 in the cells of your body because you are forming 938 00:43:49,060 --> 00:43:52,810 these superoxide radicals and hydrogen peroxide 939 00:43:52,810 --> 00:43:54,190 all the time in your cells. 940 00:43:54,190 --> 00:43:56,950 And this reaction is happening on this scale, or the reaction 941 00:43:56,950 --> 00:44:00,130 that you just saw is happening this many times faster 942 00:44:00,130 --> 00:44:03,790 in your body, and you will see it happen also in your flask. 943 00:44:03,790 --> 00:44:08,285 So any questions, thoughts? 944 00:44:10,960 --> 00:44:12,280 No? 945 00:44:12,280 --> 00:44:14,290 All right, well, thank you guys. 946 00:44:14,290 --> 00:44:16,320 You can head to lab.