Lec. 13. "Clean Natural Gases" and More Review Problems
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Shaka, A.J.
 UCI Chem 1B is the second quarter of General Chemistry and covers the following topics: properties of gases, liquids, solids; changes of state; properties of solutions; stoichiometry; thermochemistry; and thermodynamics.
 the cost of going to UC is going up. I thought I'd just tell you what I would do if I were in charge and when I present what I would do you'll see why I'm not in charge. If I were in charge it would be free. But if you weren't serious you'd be gone. No repeats you'd flunk one course. Sayonara. Because if it's free there are going to be a lot of people who are willing to take your shoes. So you don't move around, you don't march around, you don't do anything except work. And you try to improve yourself as much as you possibly can. And then after you graduate, if you go to graduate or professional school we defer things. But after you graduate we take 5% of what you earn for the next 10 years. If I don't teach you anything worthwhile then you're a barista at Starbucks I don't get paid off. But if I teach you something incredibly valuable and you get a high paying job then I get rewarded for doing that. On the other hand if you take 4 years of college and then you get sick or hit by a car and you're on disability you aren't on the hook for 50,000 bucks but now you can't possibly pay back. If you don't have the stress you have an opportunity everyone can go but if you don't work you're out of there. That's how I would do it. We'd have to settle on the percentage, we'd have to make the numbers work but it could be done. Okay I keep hearing on the news all these people dying and what's getting alarming is that they aren't that much older than I am. So it's starting to become sort of a constant drumbeat with dawn and summer dying and so and so dying. The question is did they do something wrong or were they unlucky or some combination of both? The answer is you usually make your own luck. Do you remember the ancient saying, man sana in cook pro sana, a sound mind and a sound body. That's the Aristotelian ideal and that's what you should strive for and you shouldn't assume that that's going to be easy. No one said easy. Easy is your friend, it's what makes you tougher and makes you have the ability to withstand all the knocks that you're going to get in life. You don't want things too easy. Maybe that's why the rich movie stars and rock stars don't live long. Things are too easy and they're unmotivated to do anything and without the motivation you don't do anything and then you die. People who retire early die quicker. They think, yeah, great, I can now retire early. Statistically they die much quicker than people who keep working. That's kind of the same thing. Let's have a look. I just had to inject a little bit about something that concerns me. I keep seeing on these clips, clean natural gas and I'm sure you all think it's probably a positive opinion that I don't know. You may have forgotten the San Bruno blow up that leveled all those houses but that doesn't happen that often. There is a lot of natural gas that can be obtained by unconventional methods and I'd just like to have a look. The method that they're using all over the United States now is called hydraulic fracturing. I'll tell you a little bit about it. You access so-called shale gas and boy is it being carried out at huge scale. Many people in the United States do not own the mineral rights to their property. You own the land on top but if I discover gold under your house I can drill in from the side and mine it because you do not own the mineral rights. I didn't sell you that. That's very important because most people don't read the fine print on what they do or don't own. I don't know why that's white. That's a new one. Well, let's hope it doesn't continue. Air pollution, groundwater pollution and possibly earthquakes are concerned. They've had swarms of earthquakes in Oklahoma where they didn't have any before. The methane that we get is very useful in industrial processes for heat. They're now using this gas to refine oil. They can refine the oil so cheaply into gasoline that they can afford then to ship it in ships. The gasoline to Mexico and put the Mexican refineries out of business. We're shipping gasoline down there because the price is higher. That raises our price by the way. Then also to generate electricity, unless San Onofre comes online, the AES natural gas peaker plant out in Huntington Beach is going to be fired up again and then we'll start having the brown haze and various things that we have avoided while that's been off. But if everyone switches on the air in the summer, the grid will go down unless you have enough power. Air conditioning takes a trillion watts. The price has fallen and we have jobs. Jobs for the boys. And the jobs don't require a great deal of education. So they could be ideal for certain sectors. But you have to be careful if you're doing a job that you're doing something constructive and not destructive. And sometimes it's hard to tell. The gas companies pay off farmers. Farming's kind of in a slump some years. Some guy comes along and says, look, we'll pay 100K cash. All you have to do is let us set up this little, little rig here. We'll drill way down. We'll get the gas. We'll take off. Everything will be as it was. Except you'll be richer. And of course, if you don't own the mineral rights, they just come along and set up a rig. There's a guy in Colorado who has this huge, noisy gas-drilling rig 150 feet from his house. It's producing incredible air pollution. I'll get to that in a minute. His eyes itch. Feels like somebody went down his sternum with a toilet brush. Worry's about the health of his kids. The reason why it's 150 feet away is because the law was written about 100 years ago, and they figured that if an oil derrick fell over 150 feet away, it wouldn't hit your house. The law's still on the books, and so there you go. The scale is enormous. I'll give you a little map in a minute. But it's millions and millions of gallons of water. Millions of feet of drilling, and all over the place. It's a big boom. So then, if it's natural gas, our energy, panacea, even if there's a lot of it. If I'm a diabetic, it doesn't matter if I have a thousand chocolate cakes. Maybe not. So here's an article. One thing you should do is you should go to the library, and you should learn how to use a proper search engine like PubMed or ISI Web of Science or these various search engines. You should find topics that interest you, and then find articles written in refereed journals. You'd not a blog, a refereed journal. Somebody else who's an expert read the manuscript and said, yeah, there may be some problems with it, but, or you may want to do this experiment, and then we'll let you publish it, et cetera. And read those. And if you can't understand them, then you know you need to learn a lot more. When you first start out, you won't be able to understand a thing about the article. It'll have notation, jargon, abbreviations, et cetera. But gradually, as you read more of them, you'll start to come up to speed, and you'll be able to educate yourself then. And that's really a huge benefit of the access, the electronic access that we have. And of course, books are not half bad either, and there are plenty of them in the Science Library. Now here's an article that came out in 2011. Methane and the greenhouse gas footprint of natural gas from shale formations. If you're interested in what's going on, then this is an interesting article. And they say, OK, we evaluate the greenhouse gas footprint of natural gas obtained by high volume hydraulic fracturing from shale formations focusing on methane emissions. I've blown this up a little so it's easier to read. Methane itself, not CO2, but methane itself is a powerful greenhouse gas with a global warming potential that is far greater than that of carbon dioxide, particularly over the time horizon of the first few decades following emission. Methane contributes substantially to the greenhouse gas footprint of shale gas on shorter times scales, dominating it on a 20-year time horizon. The footprint for shale gas is greater than that for conventional gas or oil when viewed on any time horizon, but particularly over 20 years. And here's the bad part. Compared to coal, that's the worst of the worst. The footprint of shale gas is at least 20% greater. And perhaps more than twice as great on the 20-year time horizon. And it's comparable when compared over 100 years. The problem is, as I've mentioned several times why chemists don't like to work with gases, is gases always leak. No matter what you do, you have leaks. And if you're bringing up millions and millions of cubic feet of natural gas, all of which you're going to burn, by the way, into CO2 anyhow, which isn't a good idea, but let's leave that out, and a few percent leak. And it's 20 times more potent than the CO2 you produce from it. Then you've doubled your greenhouse gas footprint. In other words, you're going to autoclave the whole planet by doing that. And here's a graph from this paper, the 20-year time horizon. They have a low estimate, grams of carbon per megajoule of energy. A high estimate depends how much leaks and a lot of stuff. And this is the methane. The purple is the huge part. This is the CO2 after you burn it. And this is indirect CO2. Indirect CO2 is, last time I checked when you set up a drilling rig, you have to power it somehow. While if you power it with diesel, you're creating a ton of CO2. And it takes a lot of muscle to drill down 8,000 feet and then pump in billions of gallons of water to do the hydraulic fracturing. Let's have a look. This is what they do. They start up here, then they come down. And then they've got tricky technology now. This is why it's unconventional. So they can turn the corner and they can drill in to this big layer of dark-looking, marcellous shale that has a lot of gas trapped in it in tiny pores. Then they set off some high explosives. Usually they don't mention that, but that's pretty much part of mining last time I checked. There's a lot of explosions that go on. And then they pump down a ton of water and other stuff. The other stuff pollutes the water and the water gets polluted here as well because the reason this is shale is that this is an ancient marine formation and so it's got a ton of salt in it and other things. And when the water comes back up, it's polluted. You can't drink it, you can't use it for farming, you can't do anything with it, you have to treat it. And that treatment is going to cost energy. And it could be a lot. In fact, you could come out in the hole if you aren't careful. This is what a real rig looks like. They're big, they're loud, and they wreck the air for a long ways around because when you have methane leak out, you get a lot of ozone formation and that's what makes your eyes itch and your throat burn and so forth. That's the air pollution on a very bad day when it looks grayish and you can't see anything. That's ozone in the troposphere. That's known to be bad. There are organisms, I think, that can live on hydrogen cyanide but nothing can live on ozone. Ozone kills everything. So they drill 8,000 feet down, lots of pipes going down there, then 11,000 feet sideways and then millions of gallons of what they call frack fluid which has things like hydrochloric acid and all sorts of things in it. And here are the trucks delivering all the stuff and all the truck drivers have jobs and here they've cleared this area. This used to be green like this and now it looks like that. There's an environmental consequence for doing that because you have to build all these roads into everywhere, wreck the forest as you go. And then this is, each little dot here like smallpox is a well in West Virginia. These are all hitting this gigantic ancient shale deposit that's underground that has a lot of gas in it. This is just West Virginia and there's Pennsylvania and now they're arguing about New York. There's Colorado. There's Montana, all these other places because now they know how to prospect for these shale formations and when they find one, if they have the rights to the mineral rights, they buy them and then they drill. And if the government owns the mineral rights and the government's broke, the government may sell it because it's worth some money. That's how things tend to go. Okay, let's do some review problems. Practice problem 47. Very topical. Let's purify some back frack. Back frack is the water that comes bubbling back out after you've pumped it down there with all those chemicals plus it's dissolved whatever happens to be down there which you may not know exactly until it comes back up what it is. I think at first they were throwing it in the rivers and then people objected to that because that was having a very big environmental impact. And then the mining company said fine, what we'll do is we'll divert the frack water to the municipal water treatment plants and that drove the municipal water treatment guys crazy because the last step when you're treating wastewater usually is you chlorinate the water to make sure it doesn't have any bacteria especially if it's from sewage and things like that. And normally that's okay. No big deal. But this has some bromide sometimes from the shale itself and if you treat bromide with chlorine you get bromine and then that reacts with various things that are in the water and you can get methyl bromide. Methyl bromide is just what they've outlawed as a fumigant for strawberries because it has a high vapor pressure and it is carcinogenic as all get out. It's a DNA methylating agent that's known bad news. You don't want that in the water that you're going to be drinking and growing stuff with. So that's out. And so now the proposal at least I read it on one brochure. The proposal is well we'll purify it by RO. We'll use reverse osmosis. Well let's figure out then how much energy that takes because we know a little bit about osmotic pressure and reverse osmosis. Let's just take a case study here and figure out what it would take. Okay. So I'm assuming that it's got 3.5% sodium chloride. This is on average and 0.2% sodium bromide. It's got a lot of other stuff. Arsenic, barium, things that chemists don't like to deal with but they can be taken out. You just have, you know, if you want to work you can clean things up. It's just like cleaning up your room. You have to want to do it and it takes work. And there are levels of clean. If you want it to be like an operating theater it's a lot more work than if you just want to look good because somebody's dropping by for a cup of tea. Well we've got our osmotic pressure equation. Pi for fancy P equals I. That just keeps track of how many moles of particles times the concentration times R times T. And we'll assume two moles of ions each from sodium chloride and sodium bromide. It's not quite two because remember these charged particles tend to try to stick together a little bit and so they aren't totally independent. And the osmotic pressure assumes they're totally independent. And let's assume 300 Kelvin depending where they're doing it. If they're doing it in the summer that's going to be quite accurate. Okay, three and a half weight percent. There are 35 grams of sodium chloride and two grams of sodium bromide per kilogram of solution which is nearly a liter of solution. Though we'll assume it is. The concentrations thus are approximately because we need the molar mass. We've got 35 grams per liter times one mole, 58.44 grams for sodium chloride. That's.6 molar. I think we did that with seawater earlier. And then we've got sodium bromide, two grams and then that's.019 molar. The total number of particles or ions is then two times the sum of these because they're both producing two moles of ions when one mole of salt dissolves. And therefore it's 1.24 molar. And then I just put this in, put in R, make sure all the units go away and I find the osmotic pressure is 30 and a half atmospheres. That means I've got to push on the water with at least that much pressure to get it to go back so I can overcome the tendency of the freshwater to rush into the salt water and push it back the other way and get freshwater out. Of course I have to have a suitable semipermeable membrane and that has to not tear or then all my polluted water comes through and it has to not clog or else I can't jam anything through. And then I need a huge pump. It's like pumping up a bike tire. As you start pumping and the tire gets full, it gets harder and harder to pump and you notice your arms get tired and there's an energy cost to doing that. Let's have a look then at what that might be. Though the 30.5 is the minimum pressure we must apply and let's just use that minimum pressure and let's just force 100 million gallons of water through at that pressure, the minimum. We need the volume of 100 million gallons in liters, 378.5 million liters and then let's just estimate just using P times V, so much pressure, so much volume going through, P V is an energy unit and we can convert it to joules by taking the ratio of the listed values of the gas constant. That's kind of a handy way to convert from liter atmospheres to joules. Just use the ratio of the gas constant. 30.5 atmospheres, I have 378 million liters, the ratio of 8.314 to.082. I get 1.2 times 10 to the 12 joules. That's 1.2 trillion. If we had a 10 megawatt reverse osmosis system, it would have to run for 120,000 seconds or about 1.25 days. This is just very, very, very crude analysis. We can do better because we can actually look up what some of the pros on reverse osmosis have said. The best estimate that I got reading the most recent literature is that it takes 5.6 kilowatt hours to purify a cubic meter for seawater. If we use that, 100 million gallons is about 378,000 cubic meters. We'll need to purify just 100 million gallons and there's a lot more water involved than that, believe me. You need 2 million kilowatt hours of electricity which has to come from somewhere, presumably by burning the gas we've just fracked. We're going round and round in a circle and a lot of stuff's getting used up. Yes? This one? Yes? Why do you assume there's two more each? Because when sodium chloride dissolves, I get Na plus and Cl minus. Remember, colligative properties depend on the number of particles but not their type. There's the total number of particles in there. That's what dictates it. Therefore if I have a mixture of things, I just have to figure out the total molarity of all the particles and that's what I need to know. To figure out the freezing point depression, the boiling point elevation, the osmotic pressure. I don't care what they are. I just care how much. Yes? Well, I assume 300 Kelvin because I had to assume a temperature for the purpose of this calculation. If I assume a high temperature, it's going to be a lot more work and then on a hot day, it may be more than 300 Kelvin. The amount of work I'm going to have to put is going to depend on how hot it is. If it's a hot day in Tennessee or something, it might be a good day to not run it, for example. Or I might want to run it in the winter. Anyway, 5.6 kilowatt hours, 2 million kilowatt hours. Even at 7 cents a kilowatt hour, if you're a big user, you might get that rate. I don't know. That's going to add up. Yes? What do you get, 120,000 seconds? I figured I had a 10-megawatt machine and that's 10 million joules per second. I know how many joules of energy I need to push it all through. I divide the two and I get the number of seconds. It came out to be about 120,000 in round numbers. Yes? No, it's two and I add up the total molarity of sodium bromide and sodium chloride first. Then each of them produces two moles of ions. Sodium chloride, sodium bromide, two each. I added up the total concentration and then multiplied by two. If I have a salt-like calcium chloride that produces three moles of ions, then what I have to do is set that aside, figure out how many moles of calcium chloride are there, and then multiply that by three and then add it in to the total. The total dissolved solids, as they call it, in these waters is very high. Some of them come out like the Great Salt Lake. In other words, the chloride is the maximum amount of chloride you can dissolve in water because these are dried out ocean deposits. They could have tons of salt in there. In actual fact, the water, this polluted water is so full of other stuff, sediment, particles of mud, stuff that's a nightmare for a reverse osmosis system because particles of mud and clay are just what you don't want with your nice semipermeable membrane because they just clog the membrane and that's it. You're out of luck. The membrane's clogged, no water goes through and now you're sitting there. Oh, well, let's change the membrane. So you have to first have a settling tank. You have to let the sediment settle. You have to make sure, and then you have to make sure that your membrane's not letting through any other nasty guys. Maybe it keeps out sodium and chloride and bromide, but lets through something else because it wasn't designed with that in mind. So you have to check it and then you have to replace the membranes and you have to put a bunch of guys on it and they have to watch it. You have to test the water that comes out to make sure it's okay and all that costs money and it could be a lot of money. So the tendency will be to not do any of it because if it costs money and I don't have to do it, there's no law that says I have to do it. I don't. Okay, practice problem 48. In this problem we'll make sure we can keep fracking in Montana in the winter. This was actually another proposed solution. I know what we'll do with all the salty water. We'll put it in some big basin and we'll let it dry and then we'll scoop up all the salt and we'll salt all the roads in the eastern U.S. in the winter time with it and de-ice the roads. And we'll be doing great public service. Unfortunately there's arsenic and other contaminants in there that they aren't going to let you just spray around everywhere so that they get into everybody's crop and everybody's well water and everything else. You're still going to have to clean it up. But anyway, here we have a problem. The cryoscopic constant for water is 1.86 degrees per molal. Suppose that a stretch of road in Montana is 70 feet wide and 10 miles long and has a one-inch thick layer of ice on it. If the ambient temperature is 20 degrees Fahrenheit, and boy does it get colder than that up there. I remember one winter in Utah we laughed every day because every day the coldest place in the inner mountain west on the weather was big, tiny Wyoming. And most of the winter it was never above zero Fahrenheit. It was minus something. And that's cold. I don't know if you've ever been in minus five degrees Fahrenheit. But if you aren't dressed for it, you're in immediate trouble. If you come out in your bathrobe to get the newspaper and the door swings shut, you might have an instant panic if the door locked and you're living in the middle of nowhere. It's that serious. It's that cold. You can die of exposure. But let's assume it's 20 Fahrenheit. The question is, I'm in charge and I need to know at the start of the day, a guy calls me up with a truck. He says, how many 50-pound bags of salt do I need today, boss? I know what the job is. I know how much snow fell. I know I have historical records of what happens with the roads. And I know that if I leave the roads icy, we're going to have a lot of accidents and a lot of misery. So I've got to de-ice the roads. How many 50-pound bags of salt should the trucks use, spreading it evenly, to make sure the road is de-iced, but without using excess salt, because salt is very bad, kills all the plants nearby? I don't want to use more than I need. And then there are all these conversion units. One degree C is 1.8 degrees F. One mile is 55,280 feet. One inch is 2.54 centimeters. One kilogram is 2.2 pounds. And the density of ice is 0.9168 grams per centimeter. This is a great problem. Let's figure out how we're going to do it. Well, we have to depress the freezing point, which is normally for pure water, 32 Fahrenheit. We have to depress the freezing point to 20 Fahrenheit. If we depress the freezing point below 20, that means the ice melts. And that's what we want. It melts and it just runs off the road. And we know what the expression is for freezing point depression. It's delta T, which is always listed as a positive number, because we always know the freezing point goes down. So we're saying delta T is some positive number, because molality is positive and the cryoscopic constant is positive. But we know that this positive is how far down it went in temperature, because it always depresses. The delta T we need, well, 12 degrees Fahrenheit, that's 32 minus 20, and then convert to Celsius. We need 6.67 degrees Celsius. And therefore, based on our freezing point depression formula, we know how many moles of particles we need. The molality of particles we need is the freezing point depression we want divided by the cryoscopic constant. 3.67 divided by 1.86 degrees C goes away, molal to the minus 1 is underneath, so it's molal. So we need 3.584 molals per kilogram of particles. That means we need half as much salt per kilogram of water. And here I'm going to leave you something to do over the weekend, which is to finish this problem. I'll tell you how to finish it, but I will not tell you the answer. One second. Here's how we finish it. We know the density of ice. We know the volume of ice. We've got 1 inch, 70 feet, 10 miles, convert that to kilograms of ice, volume times density. So figure out how much the volume of ice on that road is in cubic centimeters by converting all the units and not screwing it up. And then multiply that by 0.9168 to figure out how many grams of ice are on the road. And then divide by 1,000 to get the number of kilograms of ice on the road. Then you know for each kilogram of ice you need 1.792 moles of sodium chloride. You know the molar mass of sodium chloride. So you know how many grams of sodium chloride you need. You back convert that into pounds because the guy driving the truck, if you tell him what it is in grams, he's lost. And then you divide by 50 and say, look, Joe, load up 1,000 bags over and out. And that's what they do. And if you get it wrong, if you don't get the factor of 2, you put on twice as much salt as you need. That costs you a ton of money and wrecks the environment. And if you get it wrong and don't put on enough, they drive and waste all that diesel fuel, spraying the solution out, the salt in the road. And then it still has it. So it's important to get it right. OK? Yes? Can I repeat all that? Can I repeat all that? Guess what? I'm going to film, and I promise you that we'll have all the lectures up pronto. So just play it back. OK? Play it back and then go through it. Yes? You divide it at 3.5 and it's 4 below by 2.5? Because of I. Yes. Because I get 2 moles of particles from 1 mole of sodium chloride. And so I don't need as much sodium chloride as because I'm lucky. I get twice as much freezing point depression with sodium chloride. OK? And be prepared to solve something like this on next Tuesday. OK? Just a fun problem, converting units, fiddling around, and actually getting a practical answer. Yes? On Tuesday, because through the midterm, will we have the entire class through the midterm? Will we have the entire class to do the midterm? Yeah, pretty much. As soon as we hand things out. Pretty much. You'll have the entire class. And we'll try to hand things out as fast as we can and you can work like crazy. Yes? You said it was going to be worth the more than you're going to do on the midterm. Yes. It will be. I don't know how much more. But it'll, yeah. I can't hear you. The website for the lecture video. The first ones are on our class website. Go down to the bottom. Click and you can find. And this will be whatever lecture it is. I think this is 12. OK? If you want to play this one back, in particular. OK. Let's press on. Here's problem 49. Aha. What is this one? Benzene. Benzene. Oi. There's been a long history of things like benzene. Benzene used to be used as a solvent in organic chemistry labs like crazy. Everybody used it. Except benzene, well it's known that benzene is poisonous. But benzene is also a class A carcinogen. And one day a crate of benzene came in and it was marked different than before. It was just benzene, analytical grade, ready to roll. This one was brightly colored like if you don't pay your power bill. And it said all these hazardous warnings and I thought, gee, it would have been nice to know that back then. And there's a moral to that story. If the science hasn't been done, you're on your own. It could be hazardous or not. Nobody knows yet. And therefore the wisest thing is to be cautious. Don't expose yourself to all kinds of new things just because they're new. If there's no evidence about what they may or may not do. You have to be kind of cautious. I'm still here though, so probably wasn't that bad. I also washed my hands with chloroform one time. Another class A carcinogen because I had something nasty on my hands which was even worse. And it was bugging me because it was staining my skin bright yellow and I thought that's probably not good. I know, get it off with chloroform. You could never do that these days either. That was a very long time ago. Okay. Benzene here in skeletal formation has a carbon and a hydrogen at each position. So it's C6H6. And I've drawn it here as alternating single and double bonds, but it in fact is a perfect hexagon so it can't possibly be single and double alternating or it would be distorted. So the bonds swap around as you may know, that's called resonance. And here we have a list of all the mean bond enthalpy's for a C-H bond for 12 for a C-C single bond, 348 kilojoules per mole, C-C double bond, 614, CO double bond, almost 800, O-O double bond in oxygen, 495, and an OH single bond, 463. And with this table here, I can work out the enthalpy of combustion of benzene. I can estimate it. So first we have to balance the complete combustion reaction. I have six carbons. Therefore the first, I always write CO2 and H2O for complete combustion. I have six carbons and that means I've got to have a six there. I have six hydrogens, H, this is the only thing with hydrogen, so I need three of these guys. And then all I do is carefully count up the oxygen, which won't matter for the combustion reaction enthalpy because oxygen has, well actually I take that all back. This matters a lot because we need to know how many oxygen bonds we're breaking because we aren't doing it by formation. I've got 12 oxygens here plus three, that's 15. This is molecular oxygen so I need 15 halves. The next thing we have to do is we have to count and boy you've got to be careful if you're under pressure because if you miscount you get it wrong. You can know exactly how to do it but if you miscount or you flub it with the calculator you just get it wrong anyway. Still wrong. We count all the bonds in the reactants and products. For benzene we've got three carbon-carbon single bonds, those are the single lines, three carbon-carbon double bonds, those are the double lines and then we've got six hydrogens around the ring, so that's six carbon-hydrogen single bonds. For oxygen we've got seven and a half, we're just using the numbers, seven and a half OO double bonds. For carbon dioxide we've got six of them but each has two CO double bonds. Again, we've got to count the bonds so that's 12 CO double bonds and for water we've got two OH single bonds but we've got three of them so we've got six OH bonds. Just as an aside chemists often write notations of the form AXN like SO4 or PO4 or CLO4 NO3, there's lots of things like that. Whenever it's written like that AXN it means that all the X's are independently stuck onto the A like the spokes of a bicycle into the hub and that's how you can count the bonds if you're just given the formula. If it's not written like that it's still maybe like that, H2O for historical reasons we don't write OH2, that would be consistent but we're so used to calling it H2O that we keep it in that order but that's got an H and H and then the oxygen. If you don't know how they're bonded you can't count the number of bonds. If you just have a formula and you don't know who's bonded to whom you can't count the number of bonds and so you can't get it done. So you have to know the structure to be able to count. Let's then take these and let's count them up. I don't think it's too bad. Let's break all the reactant bonds. We got three carbon single bonds, three carbon double bonds, six carbon hydrogen single bonds and seven and a half OO double bonds and that turns out to add up to quite a lot 9,070.5 kilojoules per mole. And then let's take all the energy to break the product bonds. We've got 12 carbon oxygen double bonds, that's 12 times 799 plus 6 hydrogen oxygen single bonds, 6 times 463, that's even bigger, 12,366. We're making the products though. We aren't breaking the products into atoms. What we're doing conceptually is we're breaking the reactants into atoms and then we're reassembling the atoms in another way like tinker toys into the product. And therefore we don't want this plus energy to make the products. We get this energy back when we make them. And therefore the delta H of combustion is 9,070.5 minus the 12,366 and that's minus 3,295.5 kilojoules per mole. That's our estimate. I looked in the CRC and the literature value is minus 3,273 kilojoules per mole. It's off by 22 or so. A benzene by this figure appears to be more stable than what we figured. That might be, these numbers are kind of big, it might be because of our approximate nature of the calculation using these averages over a library of compounds. But in fact, benzene is more stable than we would have predicted. And that has consequences because benzene's more stable and also benzene's stuck together to make bigger things like pyrenes and molecules like that are also more stable. And that means for example in cigarette smoke where you don't have complete combustion, you have particles that have a lot of things like benz-pyrene and things like that on them. And if you take a mouse and you take benz-pyrene and you paint it on their skin, they get cancer right where you painted it. Not good stuff. If you're ever working with that, you have to be extremely careful because if you get it on your skin, that can be it. Now you're exposed. Okay, practice problem 50. Let's go way back. Was it just so beautiful or so horrible? Interesting how you can think back. It seems so long ago, doesn't it? How far we've come? Barium titanate is a piezoelectric material. A piezoelectric material is a material that if you put an electrical force on it, if you put an electric potential on it, it will mechanically deform. Or if you mechanically deform it, it will start generating an electric potential. You may have heard the phrase piezoelectric tweeters because they use some of these materials in loudspeakers because they put a voltage on and it mechanically deforms at the same frequency as the voltage. That shakes the air and then you hear the symbol crash. The fidelity can be quite good. Here's a material, barium titanate. Here it is in this big unit cell here. The question is, if this is the unit cell for barium titanate, what is the molecular formula for barium titanate? It sort of depends on how good your brain is at figuring out where spheres are. Usually we would try to put some planes through some sort of dark circle through the thing. But I'll just tell you that these oxygens are on the middle of the faces. They're on the edge. They aren't inside. These guys here are on the exact corner and this guy here is totally inside the box. We're going to use that to get the formula. For, although we draw it like this, the real unit cell is all shaved off because it has to be a perfect cube so when we put them together we make an entire crystal. We can't have extra stuff hanging out over the edges. We can only count what's inside the box, not what's outside. Although we tend not to draw it that way because that turns out to be even more confusing than drawing it this way. People have a hard time seeing. Okay, let's look. The barium atoms are on the corners. They're intersected by three planes. Therefore they only count one-eighth. Or if you imagine it's only the inner part on the corner, the outer parts are all gone. That's one-eighth. There's eight of them so there's one barium atom. The titanium atoms completely inside and so there's one titanium per unit cell. The six oxygen atoms are on the six faces. They have one plane through them so they count half. There's six of them. Six times a half is three. The charges also help us although the charges are not always listed with the unit cell. Sometimes they aren't theirs. But in this case they are. It was listed plus two for barium. Well that's an alkaline earth metal. Plus four for titanium. That's a common oxidation state for titanium. And then three times two minus for oxygen. This is six positive and six negative. The salt's neutral just like sodium chloride is neutral. Sodium plus chloride minus. And so the formula is BATIO3. And that's why it's called barium titanate. It's purportedly being used as part of the new capacitor storage systems being investigated for next generation vehicles. So next generation vehicles they may have a big for electric vehicle. They may have a big capacitor in the vehicle too in addition to the battery. And when you really need to go the capacitor discharges and supplies you a lot of power very quickly. And then while you're coasting downhill the car is smart enough to charge the capacitor back up like it does the battery. Yeah. What would happen on a test if you accidentally broke titanium, like titanium barium oxygen 3? I'd give it to you because you aren't a chemist yet. But the reason why it's called barium titanate and sodium chloride when you see the one that has the IUM that's first. IUM? Yeah. Sodium. Barium. Okay. Otherwise it'd be called titanium bariate or something like that if it were backwards. But for now we won't split hairs. Okay. If you get the right number of atoms we'll take it. Okay. All right. Let's see. Aha. A temperature sensitive, oops I meant compound. I've got a temper, I'll fix that. A temperature sensitive compound that is wet. I can't heat it to dry it because if I heat it it decomposes. It cooks. Now I made this stuff in the lab and the last thing I want to do on the last step to dry it out to weigh it is to cook it. And so I want to get rid of the water but not by heating it up to 100 so that the water vapor pressure is one atmosphere. But I just want to heat it up to 40. And if I know the enthalpy of vaporization of water then I should know if I have a pump in a speedback what pressure I need to hold on the pump in order to be able to drive the water off only at 40 Celsius. I don't want the pressure to be higher than the vapor pressure of water at 40 Celsius. If it's higher the water will go back onto the compound. If my pressure is lower because I'm pumping fast enough then the water will just wander off and I'll dry it out and I won't wreck the compound. This is done all the time in the lab. We need an equation then that relates delta H of vaporization to temperature and I see ooh these are in Celsius. Be careful. While we have such an equation the Clausius-Clapeyron equation and it says if I know the vapor pressure at one temperature then I can predict the vapor pressure at another temperature as long as I know delta H but I know delta H and I know R should be fairly easy. The only thing I have to be careful of is this 40 Celsius. If I'm in a hurry I might put 1 over 100, 1 over 40 and I'll get into trouble right away. Let's insert all the numbers. I'm calling conditions one. Conditions one is water at 100 Celsius and one atmosphere pressure. So I put P1, 1 atmosphere, P2 I want to figure out. This is delta H in joules. This is R in joules. Formol goes away. Calvin to the minus 1 that kills this. Good. The log of something is dimensionless. I convert the 100 to 373.15 and I convert the 40 to 313.15 and then I solve all this stuff and I get a number plus 2.5104 and then I take the exponential function of both sides which just gets rid of the log. I have one atmosphere divided by P2 is equal to the exponential function or e to the 2.5. I punch e to the 2.5 on my calculator. I get 12.31, therefore P2 is 1 over 12.31. P2 is 0.0812 atmospheres or 61.7 Tor. Oftentimes the meter will actually be listed in Tor just because people find it easier to read 60 Tor than 0.08 something in atmosphere. I know the vapor pressure of water is one atmosphere at its boiling point. That I do know. We can achieve this with any decent pump. We had to make some assumptions that the material itself has very low vapor pressure if the material has high vapor pressure will actually pump it off too and you have to be careful sometimes depending what you've got. Otherwise you end up pumping your product into the pump oil of the pump and then people get very angry with you when you pump things into the pump oil because that wrecks the pump oil for the next person. That's one. 52. A careless scientist has measured the vapor pressure of toluene. That's the stuff in airplane glue that kids got into for a while. None of them were chemists I assure you. Chemists do not sniff anything ever. I measured the vapor pressure of toluene in atmospheres here. The boiling point of toluene is about 110. To me this data looks okay. And then after the measurement, now the goal of the project was to determine delta H of vaporization for toluene. Well I've got all this data. This is much, much better than two points because if I can plot this data as a straight line I can then do linear regression and I can get a great line through all of it. And then I can get the slope of that line and that's minus delta H over R. So I can get it. Just have to do a little analysis. Well here's what happened. He plots log P versus one over T and comes to you and says help boss, help. It's not straight. What's going wrong? He took the log okay I guess. First of all what's wrong with this graph? The axes are not labeled with the units. Before you see a graph where the axes are not labeled, stand back. Don't start looking at the graph. Try to figure out what the units were. He had things like 20 degrees and I notice he's got 05 and I notice that one over 20 is 0.05. And so I figured this guy's adult. What he's done is he's plotted the log of the pressure okay but he's plotted it versus one over T in Celsius. And that's why it's curved because it has to be one over T in Kelvin and he's careless because he didn't put the units here which should be K to the minus one or in his case degrees C to the minus one. If you would have seen degrees C to the minus one you would have said hey that's wrong. You never plot anything in chemistry like that. We always use Kelvin and therefore if you go back and do it and so here's the conclusion. The data's okay. The graph doesn't have units. We can see that the log of the pressure's okay because you can take the log of that and the reference pressure is one atmosphere. But it's in Celsius okay. And what I'd like you to do is go back, convert it to Kelvin, plot it and see if it's straight. And then here are the last important points for Tuesday. First, same seating chart. Second, we have to do some spot roll taking. Therefore make sure you have your ID because somebody will come around and say you're in G7 or you Joe Blow. Third, practice. And finally, don't count on looking things up in your notes. Just slow algorithm. And I hope you do well.
 the cost of going to UC is going up.  I thought I'd just tell you what I would do if I were in charge and when I present  what I would do you'll see why I'm not in charge.  If I were in charge it would be free.  But if you weren't serious you'd be gone.  No repeats you'd flunk one course.  Sayonara.  Because if it's free there are going to be a lot of people who are willing to take your  shoes.  So you don't move around, you don't march around, you don't do anything except work.  And you try to improve yourself as much as you possibly can.  And then after you graduate, if you go to graduate or professional school we defer things.  But after you graduate we take 5% of what you earn for the next 10 years.  If I don't teach you anything worthwhile then you're a barista at Starbucks I don't  get paid off.  But if I teach you something incredibly valuable and you get a high paying job then I get rewarded  for doing that.  On the other hand if you take 4 years of college and then you get sick or hit by a car and  you're on disability you aren't on the hook for 50,000 bucks but now you can't possibly  pay back.  If you don't have the stress you have an opportunity everyone can go but if you don't work you're  out of there.  That's how I would do it.  We'd have to settle on the percentage, we'd have to make the numbers work but it could  be done.  Okay I keep hearing on the news all these people dying and what's getting alarming is that  they aren't that much older than I am.  So it's starting to become sort of a constant drumbeat with dawn and summer dying and so  and so dying.  The question is did they do something wrong or were they unlucky or some combination of  both?  The answer is you usually make your own luck.  Do you remember the ancient saying, man sana in cook pro sana, a sound mind and a sound  body.  That's the Aristotelian ideal and that's what you should strive for and you shouldn't  assume that that's going to be easy.  No one said easy.  Easy is your friend, it's what makes you tougher and makes you have the ability to withstand  all the knocks that you're going to get in life.  You don't want things too easy.  Maybe that's why the rich movie stars and rock stars don't live long.  Things are too easy and they're unmotivated to do anything and without the motivation  you don't do anything and then you die.  People who retire early die quicker.  They think, yeah, great, I can now retire early.  Statistically they die much quicker than people who keep working.  That's kind of the same thing.  Let's have a look.  I just had to inject a little bit about something that concerns me.  I keep seeing on these clips, clean natural gas and I'm sure you all think it's probably  a positive opinion that I don't know.  You may have forgotten the San Bruno blow up that leveled all those houses but that doesn't  happen that often.  There is a lot of natural gas that can be obtained by unconventional methods and I'd  just like to have a look.  The method that they're using all over the United States now is called hydraulic fracturing.  I'll tell you a little bit about it.  You access so-called shale gas and boy is it being carried out at huge scale.  Many people in the United States do not own the mineral rights to their property.  You own the land on top but if I discover gold under your house I can drill in from  the side and mine it because you do not own the mineral rights.  I didn't sell you that.  That's very important because most people don't read the fine print on what they do  or don't own.  I don't know why that's white.  That's a new one.  Well, let's hope it doesn't continue.  Air pollution, groundwater pollution and possibly earthquakes are concerned.  They've had swarms of earthquakes in Oklahoma where they didn't have any before.  The methane that we get is very useful in industrial processes for heat.  They're now using this gas to refine oil.  They can refine the oil so cheaply into gasoline that they can afford then to ship it in ships.  The gasoline to Mexico and put the Mexican refineries out of business.  We're shipping gasoline down there because the price is higher.  That raises our price by the way.  Then also to generate electricity, unless San Onofre comes online, the AES natural gas  peaker plant out in Huntington Beach is going to be fired up again and then we'll start  having the brown haze and various things that we have avoided while that's been off.  But if everyone switches on the air in the summer, the grid will go down unless you have  enough power.  Air conditioning takes a trillion watts.  The price has fallen and we have jobs.  Jobs for the boys.  And the jobs don't require a great deal of education.  So they could be ideal for certain sectors.  But you have to be careful if you're doing a job that you're doing something constructive  and not destructive.  And sometimes it's hard to tell.  The gas companies pay off farmers.  Farming's kind of in a slump some years.  Some guy comes along and says, look, we'll pay 100K cash.  All you have to do is let us set up this little, little rig here.  We'll drill way down.  We'll get the gas.  We'll take off.  Everything will be as it was.  Except you'll be richer.  And of course, if you don't own the mineral rights, they just come along and set up a  rig.  There's a guy in Colorado who has this huge, noisy gas-drilling rig 150 feet from his house.  It's producing incredible air pollution.  I'll get to that in a minute.  His eyes itch.  Feels like somebody went down his sternum with a toilet brush.  Worry's about the health of his kids.  The reason why it's 150 feet away is because the law was written about 100 years ago, and  they figured that if an oil derrick fell over 150 feet away, it wouldn't hit your house.  The law's still on the books, and so there you go.  The scale is enormous.  I'll give you a little map in a minute.  But it's millions and millions of gallons of water.  Millions of feet of drilling, and all over the place.  It's a big boom.  So then, if it's natural gas, our energy, panacea, even if there's a lot of it.  If I'm a diabetic, it doesn't matter if I have a thousand chocolate cakes.  Maybe not.  So here's an article.  One thing you should do is you should go to the library, and you should learn how to use  a proper search engine like PubMed or ISI Web of Science or these various search engines.  You should find topics that interest you, and then find articles written in refereed  journals.  You'd not a blog, a refereed journal.  Somebody else who's an expert read the manuscript and said, yeah, there may be some problems  with it, but, or you may want to do this experiment, and then we'll let you publish it, et cetera.  And read those.  And if you can't understand them, then you know you need to learn a lot more.  When you first start out, you won't be able to understand a thing about the article.  It'll have notation, jargon, abbreviations, et cetera.  But gradually, as you read more of them, you'll start to come up to speed, and you'll be able  to educate yourself then.  And that's really a huge benefit of the access, the electronic access that we have.  And of course, books are not half bad either, and there are plenty of them in the Science  Library.  Now here's an article that came out in 2011.  Methane and the greenhouse gas footprint of natural gas from shale formations.  If you're interested in what's going on, then this is an interesting article.  And they say, OK, we evaluate the greenhouse gas footprint of natural gas obtained by high  volume hydraulic fracturing from shale formations focusing on methane emissions.  I've blown this up a little so it's easier to read.  Methane itself, not CO2, but methane itself is a powerful greenhouse gas with a global  warming potential that is far greater than that of carbon dioxide, particularly over  the time horizon of the first few decades following emission.  Methane contributes substantially to the greenhouse gas footprint of shale gas on shorter times  scales, dominating it on a 20-year time horizon.  The footprint for shale gas is greater than that for conventional gas or oil when viewed  on any time horizon, but particularly over 20 years.  And here's the bad part.  Compared to coal, that's the worst of the worst.  The footprint of shale gas is at least 20% greater.  And perhaps more than twice as great on the 20-year time horizon.  And it's comparable when compared over 100 years.  The problem is, as I've mentioned several times why chemists don't like to work with  gases, is gases always leak.  No matter what you do, you have leaks.  And if you're bringing up millions and millions of cubic feet of natural gas, all of which  you're going to burn, by the way, into CO2 anyhow, which isn't a good idea, but let's  leave that out, and a few percent leak.  And it's 20 times more potent than the CO2 you produce from it.  Then you've doubled your greenhouse gas footprint.  In other words, you're going to autoclave the whole planet by doing that.  And here's a graph from this paper, the 20-year time horizon.  They have a low estimate, grams of carbon per megajoule of energy.  A high estimate depends how much leaks and a lot of stuff.  And this is the methane.  The purple is the huge part.  This is the CO2 after you burn it.  And this is indirect CO2.  Indirect CO2 is, last time I checked when you set up a drilling rig, you have to power  it somehow.  While if you power it with diesel, you're creating a ton of CO2.  And it takes a lot of muscle to drill down 8,000 feet and then pump in billions of gallons  of water to do the hydraulic fracturing.  Let's have a look.  This is what they do.  They start up here, then they come down.  And then they've got tricky technology now.  This is why it's unconventional.  So they can turn the corner and they can drill in to this big layer of dark-looking, marcellous  shale that has a lot of gas trapped in it in tiny pores.  Then they set off some high explosives.  Usually they don't mention that, but that's pretty much part of mining last time I checked.  There's a lot of explosions that go on.  And then they pump down a ton of water and other stuff.  The other stuff pollutes the water and the water gets polluted here as well because the  reason this is shale is that this is an ancient marine formation and so it's got a ton of  salt in it and other things.  And when the water comes back up, it's polluted.  You can't drink it, you can't use it for farming, you can't do anything with it, you  have to treat it.  And that treatment is going to cost energy.  And it could be a lot.  In fact, you could come out in the hole if you aren't careful.  This is what a real rig looks like.  They're big, they're loud, and they wreck the air for a long ways around because when  you have methane leak out, you get a lot of ozone formation and that's what makes your  eyes itch and your throat burn and so forth.  That's the air pollution on a very bad day when it looks grayish and you can't see anything.  That's ozone in the troposphere.  That's known to be bad.  There are organisms, I think, that can live on hydrogen cyanide but nothing can live on  ozone.  Ozone kills everything.  So they drill 8,000 feet down, lots of pipes going down there, then 11,000 feet sideways  and then millions of gallons of what they call frack fluid which has things like hydrochloric  acid and all sorts of things in it.  And here are the trucks delivering all the stuff and all the truck drivers have jobs  and here they've cleared this area.  This used to be green like this and now it looks like that.  There's an environmental consequence for doing that because you have to build all these  roads into everywhere, wreck the forest as you go.  And then this is, each little dot here like smallpox is a well in West Virginia.  These are all hitting this gigantic ancient shale deposit that's underground that has  a lot of gas in it.  This is just West Virginia and there's Pennsylvania and now they're arguing about New York.  There's Colorado.  There's Montana, all these other places because now they know how to prospect for these shale  formations and when they find one, if they have the rights to the mineral rights, they  buy them and then they drill.  And if the government owns the mineral rights and the government's broke, the government  may sell it because it's worth some money.  That's how things tend to go.  Okay, let's do some review problems.  Practice problem 47.  Very topical.  Let's purify some back frack.  Back frack is the water that comes bubbling back out after you've pumped it down there  with all those chemicals plus it's dissolved whatever happens to be down there which you  may not know exactly until it comes back up what it is.  I think at first they were throwing it in the rivers and then people objected to that  because that was having a very big environmental impact.  And then the mining company said fine, what we'll do is we'll divert the frack water to  the municipal water treatment plants and that drove the municipal water treatment guys crazy  because the last step when you're treating wastewater usually is you chlorinate the water  to make sure it doesn't have any bacteria especially if it's from sewage and things  like that.  And normally that's okay.  No big deal.  But this has some bromide sometimes from the shale itself and if you treat bromide with  chlorine you get bromine and then that reacts with various things that are in the water  and you can get methyl bromide.  Methyl bromide is just what they've outlawed as a fumigant for strawberries because it  has a high vapor pressure and it is carcinogenic as all get out.  It's a DNA methylating agent that's known bad news.  You don't want that in the water that you're going to be drinking and growing stuff with.  So that's out.  And so now the proposal at least I read it on one brochure.  The proposal is well we'll purify it by RO.  We'll use reverse osmosis.  Well let's figure out then how much energy that takes because we know a little bit about  osmotic pressure and reverse osmosis.  Let's just take a case study here and figure out what it would take.  Okay.  So I'm assuming that it's got 3.5% sodium chloride.  This is on average and 0.2% sodium bromide.  It's got a lot of other stuff.  Arsenic, barium, things that chemists don't like to deal with but they can be taken out.  You just have, you know, if you want to work you can clean things up.  It's just like cleaning up your room.  You have to want to do it and it takes work.  And there are levels of clean.  If you want it to be like an operating theater it's a lot more work than if you just want  to look good because somebody's dropping by for a cup of tea.  Well we've got our osmotic pressure equation.  Pi for fancy P equals I. That just keeps track of how many moles of particles times the concentration  times R times T. And we'll assume two moles of ions each from sodium chloride and sodium  bromide.  It's not quite two because remember these charged particles tend to try to stick together  a little bit and so they aren't totally independent.  And the osmotic pressure assumes they're totally independent.  And let's assume 300 Kelvin depending where they're doing it.  If they're doing it in the summer that's going to be quite accurate.  Okay, three and a half weight percent.  There are 35 grams of sodium chloride and two grams of sodium bromide per kilogram of  solution which is nearly a liter of solution.  Though we'll assume it is.  The concentrations thus are approximately because we need the molar mass.  We've got 35 grams per liter times one mole, 58.44 grams for sodium chloride.  That's.6 molar.  I think we did that with seawater earlier.  And then we've got sodium bromide, two grams and then that's.019 molar.  The total number of particles or ions is then two times the sum of these because they're  both producing two moles of ions when one mole of salt dissolves.  And therefore it's 1.24 molar.  And then I just put this in, put in R, make sure all the units go away and I find the  osmotic pressure is 30 and a half atmospheres.  That means I've got to push on the water with at least that much pressure to get it to go  back so I can overcome the tendency of the freshwater to rush into the salt water and  push it back the other way and get freshwater out.  Of course I have to have a suitable semipermeable membrane and that has to not tear or then  all my polluted water comes through and it has to not clog or else I can't jam anything  through.  And then I need a huge pump.  It's like pumping up a bike tire.  As you start pumping and the tire gets full, it gets harder and harder to pump and you  notice your arms get tired and there's an energy cost to doing that.  Let's have a look then at what that might be.  Though the 30.5 is the minimum pressure we must apply and let's just use that minimum  pressure and let's just force 100 million gallons of water through at that pressure,  the minimum.  We need the volume of 100 million gallons in liters, 378.5 million liters and then let's  just estimate just using P times V, so much pressure, so much volume going through, P  V is an energy unit and we can convert it to joules by taking the ratio of the listed  values of the gas constant.  That's kind of a handy way to convert from liter atmospheres to joules.  Just use the ratio of the gas constant.  30.5 atmospheres, I have 378 million liters, the ratio of 8.314 to.082.  I get 1.2 times 10 to the 12 joules.  That's 1.2 trillion.  If we had a 10 megawatt reverse osmosis system, it would have to run for 120,000 seconds or  about 1.25 days.  This is just very, very, very crude analysis.  We can do better because we can actually look up what some of the pros on reverse osmosis  have said.  The best estimate that I got reading the most recent literature is that it takes 5.6 kilowatt  hours to purify a cubic meter for seawater.  If we use that, 100 million gallons is about 378,000 cubic meters.  We'll need to purify just 100 million gallons and there's a lot more water involved than  that, believe me.  You need 2 million kilowatt hours of electricity which has to come from somewhere, presumably  by burning the gas we've just fracked.  We're going round and round in a circle and a lot of stuff's getting used up.  Yes?  This one?  Yes?  Why do you assume there's two more each?  Because when sodium chloride dissolves, I get Na plus and Cl minus.  Remember, colligative properties depend on the number of particles but not their type.  There's the total number of particles in there.  That's what dictates it.  Therefore if I have a mixture of things, I just have to figure out the total molarity  of all the particles and that's what I need to know.  To figure out the freezing point depression, the boiling point elevation, the osmotic pressure.  I don't care what they are.  I just care how much.  Yes?  Well, I assume 300 Kelvin because I had to assume a temperature for the purpose of this  calculation.  If I assume a high temperature, it's going to be a lot more work and then on a hot day,  it may be more than 300 Kelvin.  The amount of work I'm going to have to put is going to depend on how hot it is.  If it's a hot day in Tennessee or something, it might be a good day to not run it, for  example.  Or I might want to run it in the winter.  Anyway, 5.6 kilowatt hours, 2 million kilowatt hours.  Even at 7 cents a kilowatt hour, if you're a big user, you might get that rate.  I don't know.  That's going to add up.  Yes?  What do you get, 120,000 seconds?  I figured I had a 10-megawatt machine and that's 10 million joules per second.  I know how many joules of energy I need to push it all through.  I divide the two and I get the number of seconds.  It came out to be about 120,000 in round numbers.  Yes?  No, it's two and I add up the total molarity of sodium bromide and sodium chloride first.  Then each of them produces two moles of ions.  Sodium chloride, sodium bromide, two each.  I added up the total concentration and then multiplied by two.  If I have a salt-like calcium chloride that produces three moles of ions, then what I  have to do is set that aside, figure out how many moles of calcium chloride are there,  and then multiply that by three and then add it in to the total.  The total dissolved solids, as they call it, in these waters is very high.  Some of them come out like the Great Salt Lake.  In other words, the chloride is the maximum amount of chloride you can dissolve in water  because these are dried out ocean deposits.  They could have tons of salt in there.  In actual fact, the water, this polluted water is so full of other stuff, sediment, particles  of mud, stuff that's a nightmare for a reverse osmosis system because particles of mud and  clay are just what you don't want with your nice semipermeable membrane because they just  clog the membrane and that's it.  You're out of luck.  The membrane's clogged, no water goes through and now you're sitting there.  Oh, well, let's change the membrane.  So you have to first have a settling tank.  You have to let the sediment settle.  You have to make sure, and then you have to make sure that your membrane's not letting  through any other nasty guys.  Maybe it keeps out sodium and chloride and bromide, but lets through something else because  it wasn't designed with that in mind.  So you have to check it and then you have to replace the membranes and you have to put  a bunch of guys on it and they have to watch it.  You have to test the water that comes out to make sure it's okay and all that costs money  and it could be a lot of money.  So the tendency will be to not do any of it because if it costs money and I don't have  to do it, there's no law that says I have to do it.  I don't.  Okay, practice problem 48.  In this problem we'll make sure we can keep fracking in Montana in the winter.  This was actually another proposed solution.  I know what we'll do with all the salty water.  We'll put it in some big basin and we'll let it dry and then we'll scoop up all the salt  and we'll salt all the roads in the eastern U.S. in the winter time with it and de-ice  the roads.  And we'll be doing great public service.  Unfortunately there's arsenic and other contaminants in there that they aren't going to let you  just spray around everywhere so that they get into everybody's crop and everybody's well  water and everything else.  You're still going to have to clean it up.  But anyway, here we have a problem.  The cryoscopic constant for water is 1.86 degrees per molal.  Suppose that a stretch of road in Montana is 70 feet wide and 10 miles long and has a  one-inch thick layer of ice on it.  If the ambient temperature is 20 degrees Fahrenheit, and boy does it get colder than  that up there.  I remember one winter in Utah we laughed every day because every day the coldest place in  the inner mountain west on the weather was big, tiny Wyoming.  And most of the winter it was never above zero Fahrenheit.  It was minus something.  And that's cold.  I don't know if you've ever been in minus five degrees Fahrenheit.  But if you aren't dressed for it, you're in immediate trouble.  If you come out in your bathrobe to get the newspaper and the door swings shut, you might  have an instant panic if the door locked and you're living in the middle of nowhere.  It's that serious.  It's that cold.  You can die of exposure.  But let's assume it's 20 Fahrenheit.  The question is, I'm in charge and I need to know at the start of the day, a guy calls  me up with a truck.  He says, how many 50-pound bags of salt do I need today, boss?  I know what the job is.  I know how much snow fell.  I know I have historical records of what happens with the roads.  And I know that if I leave the roads icy, we're going to have a lot of accidents and  a lot of misery.  So I've got to de-ice the roads.  How many 50-pound bags of salt should the trucks use, spreading it evenly, to make sure the  road is de-iced, but without using excess salt, because salt is very bad, kills all the plants  nearby?  I don't want to use more than I need.  And then there are all these conversion units.  One degree C is 1.8 degrees F. One mile is 55,280 feet.  One inch is 2.54 centimeters.  One kilogram is 2.2 pounds.  And the density of ice is 0.9168 grams per centimeter.  This is a great problem.  Let's figure out how we're going to do it.  Well, we have to depress the freezing point, which is normally for pure water, 32 Fahrenheit.  We have to depress the freezing point to 20 Fahrenheit.  If we depress the freezing point below 20, that means the ice melts.  And that's what we want.  It melts and it just runs off the road.  And we know what the expression is for freezing point depression.  It's delta T, which is always listed as a positive number, because we always know the  freezing point goes down.  So we're saying delta T is some positive number, because molality is positive and the  cryoscopic constant is positive.  But we know that this positive is how far down it went in temperature, because it always  depresses.  The delta T we need, well, 12 degrees Fahrenheit, that's 32 minus 20, and then convert to Celsius.  We need 6.67 degrees Celsius.  And therefore, based on our freezing point depression formula, we know how many moles  of particles we need.  The molality of particles we need is the freezing point depression we want divided by the cryoscopic  constant.  3.67 divided by 1.86 degrees C goes away, molal to the minus 1 is underneath, so it's  molal.  So we need 3.584 molals per kilogram of particles.  That means we need half as much salt per kilogram of water.  And here I'm going to leave you something to do over the weekend, which is to finish  this problem.  I'll tell you how to finish it, but I will not tell you the answer.  One second.  Here's how we finish it.  We know the density of ice.  We know the volume of ice.  We've got 1 inch, 70 feet, 10 miles, convert that to kilograms of ice, volume times density.  So figure out how much the volume of ice on that road is in cubic centimeters by converting  all the units and not screwing it up.  And then multiply that by 0.9168 to figure out how many grams of ice are on the road.  And then divide by 1,000 to get the number of kilograms of ice on the road.  Then you know for each kilogram of ice you need 1.792 moles of sodium chloride.  You know the molar mass of sodium chloride.  So you know how many grams of sodium chloride you need.  You back convert that into pounds because the guy driving the truck, if you tell him  what it is in grams, he's lost.  And then you divide by 50 and say, look, Joe, load up 1,000 bags over and out.  And that's what they do.  And if you get it wrong, if you don't get the factor of 2, you put on twice as much  salt as you need.  That costs you a ton of money and wrecks the environment.  And if you get it wrong and don't put on enough, they drive and waste all that diesel fuel,  spraying the solution out, the salt in the road.  And then it still has it.  So it's important to get it right.  OK?  Yes?  Can I repeat all that?  Can I repeat all that?  Guess what?  I'm going to film, and I promise you that we'll have all the lectures up pronto.  So just play it back.  OK?  Play it back and then go through it.  Yes?  You divide it at 3.5 and it's 4 below by 2.5?  Because of I. Yes.  Because I get 2 moles of particles from 1 mole of sodium chloride.  And so I don't need as much sodium chloride as because I'm lucky.  I get twice as much freezing point depression with sodium chloride.  OK?  And be prepared to solve something like this on next Tuesday.  OK?  Just a fun problem, converting units, fiddling around, and actually getting a practical answer.  Yes?  On Tuesday, because through the midterm, will we have the entire class through the midterm?  Will we have the entire class to do the midterm?  Yeah, pretty much.  As soon as we hand things out.  Pretty much.  You'll have the entire class.  And we'll try to hand things out as fast as we can and you can work like crazy.  Yes?  You said it was going to be worth the more than you're going to do on the midterm.  Yes.  It will be.  I don't know how much more.  But it'll, yeah.  I can't hear you.  The website for the lecture video.  The first ones are on our class website.  Go down to the bottom.  Click and you can find.  And this will be whatever lecture it is.  I think this is 12.  OK?  If you want to play this one back, in particular.  OK.  Let's press on.  Here's problem 49.  Aha.  What is this one?  Benzene.  Benzene.  Oi.  There's been a long history of things like benzene.  Benzene used to be used as a solvent in organic chemistry labs like crazy.  Everybody used it.  Except benzene, well it's known that benzene is poisonous.  But benzene is also a class A carcinogen.  And one day a crate of benzene came in and it was marked different than before.  It was just benzene, analytical grade, ready to roll.  This one was brightly colored like if you don't pay your power bill.  And it said all these hazardous warnings and I thought, gee, it would have been nice  to know that back then.  And there's a moral to that story.  If the science hasn't been done, you're on your own.  It could be hazardous or not.  Nobody knows yet.  And therefore the wisest thing is to be cautious.  Don't expose yourself to all kinds of new things just because they're new.  If there's no evidence about what they may or may not do.  You have to be kind of cautious.  I'm still here though, so probably wasn't that bad.  I also washed my hands with chloroform one time.  Another class A carcinogen because I had something nasty on my hands which was even worse.  And it was bugging me because it was staining my skin bright yellow and I thought that's  probably not good.  I know, get it off with chloroform.  You could never do that these days either.  That was a very long time ago.  Okay.  Benzene here in skeletal formation has a carbon and a hydrogen at each position.  So it's C6H6.  And I've drawn it here as alternating single and double bonds, but it in fact is a perfect  hexagon so it can't possibly be single and double alternating or it would be distorted.  So the bonds swap around as you may know, that's called resonance.  And here we have a list of all the mean bond enthalpy's for a C-H bond for 12 for a C-C  single bond, 348 kilojoules per mole, C-C double bond, 614, CO double bond, almost 800,  O-O double bond in oxygen, 495, and an OH single bond, 463.  And with this table here, I can work out the enthalpy of combustion of benzene.  I can estimate it.  So first we have to balance the complete combustion reaction.  I have six carbons.  Therefore the first, I always write CO2 and H2O for complete combustion.  I have six carbons and that means I've got to have a six there.  I have six hydrogens, H, this is the only thing with hydrogen, so I need three of these  guys.  And then all I do is carefully count up the oxygen, which won't matter for the combustion  reaction enthalpy because oxygen has, well actually I take that all back.  This matters a lot because we need to know how many oxygen bonds we're breaking because  we aren't doing it by formation.  I've got 12 oxygens here plus three, that's 15.  This is molecular oxygen so I need 15 halves.  The next thing we have to do is we have to count and boy you've got to be careful if  you're under pressure because if you miscount you get it wrong.  You can know exactly how to do it but if you miscount or you flub it with the calculator  you just get it wrong anyway.  Still wrong.  We count all the bonds in the reactants and products.  For benzene we've got three carbon-carbon single bonds, those are the single lines,  three carbon-carbon double bonds, those are the double lines and then we've got six hydrogens  around the ring, so that's six carbon-hydrogen single bonds.  For oxygen we've got seven and a half, we're just using the numbers, seven and a half OO  double bonds.  For carbon dioxide we've got six of them but each has two CO double bonds.  Again, we've got to count the bonds so that's 12 CO double bonds and for water we've got  two OH single bonds but we've got three of them so we've got six OH bonds.  Just as an aside chemists often write notations of the form AXN like SO4 or PO4 or CLO4 NO3,  there's lots of things like that.  Whenever it's written like that AXN it means that all the X's are independently stuck onto  the A like the spokes of a bicycle into the hub and that's how you can count the bonds  if you're just given the formula.  If it's not written like that it's still maybe like that, H2O for historical reasons we don't  write OH2, that would be consistent but we're so used to calling it H2O that we keep it  in that order but that's got an H and H and then the oxygen.  If you don't know how they're bonded you can't count the number of bonds.  If you just have a formula and you don't know who's bonded to whom you can't count the number  of bonds and so you can't get it done.  So you have to know the structure to be able to count.  Let's then take these and let's count them up.  I don't think it's too bad.  Let's break all the reactant bonds.  We got three carbon single bonds, three carbon double bonds, six carbon hydrogen single bonds  and seven and a half OO double bonds and that turns out to add up to quite a lot 9,070.5  kilojoules per mole.  And then let's take all the energy to break the product bonds.  We've got 12 carbon oxygen double bonds, that's 12 times 799 plus 6 hydrogen oxygen single  bonds, 6 times 463, that's even bigger, 12,366.  We're making the products though.  We aren't breaking the products into atoms.  What we're doing conceptually is we're breaking the reactants into atoms and then we're reassembling  the atoms in another way like tinker toys into the product.  And therefore we don't want this plus energy to make the products.  We get this energy back when we make them.  And therefore the delta H of combustion is 9,070.5 minus the 12,366 and that's minus  3,295.5 kilojoules per mole.  That's our estimate.  I looked in the CRC and the literature value is minus 3,273 kilojoules per mole.  It's off by 22 or so.  A benzene by this figure appears to be more stable than what we figured.  That might be, these numbers are kind of big, it might be because of our approximate nature  of the calculation using these averages over a library of compounds.  But in fact, benzene is more stable than we would have predicted.  And that has consequences because benzene's more stable and also benzene's stuck together  to make bigger things like pyrenes and molecules like that are also more stable.  And that means for example in cigarette smoke where you don't have complete combustion,  you have particles that have a lot of things like benz-pyrene and things like that on them.  And if you take a mouse and you take benz-pyrene and you paint it on their skin, they get cancer  right where you painted it.  Not good stuff.  If you're ever working with that, you have to be extremely careful because if you get  it on your skin, that can be it.  Now you're exposed.  Okay, practice problem 50.  Let's go way back.  Was it just so beautiful or so horrible?  Interesting how you can think back.  It seems so long ago, doesn't it?  How far we've come?  Barium titanate is a piezoelectric material.  A piezoelectric material is a material that if you put an electrical force on it, if you  put an electric potential on it, it will mechanically deform.  Or if you mechanically deform it, it will start generating an electric potential.  You may have heard the phrase piezoelectric tweeters because they use some of these materials  in loudspeakers because they put a voltage on and it mechanically deforms at the same  frequency as the voltage.  That shakes the air and then you hear the symbol crash.  The fidelity can be quite good.  Here's a material, barium titanate.  Here it is in this big unit cell here.  The question is, if this is the unit cell for barium titanate, what is the molecular  formula for barium titanate?  It sort of depends on how good your brain is at figuring out where spheres are.  Usually we would try to put some planes through some sort of dark circle through the thing.  But I'll just tell you that these oxygens are on the middle of the faces.  They're on the edge.  They aren't inside.  These guys here are on the exact corner and this guy here is totally inside the box.  We're going to use that to get the formula.  For, although we draw it like this, the real unit cell is all shaved off because it has  to be a perfect cube so when we put them together we make an entire crystal.  We can't have extra stuff hanging out over the edges.  We can only count what's inside the box, not what's outside.  Although we tend not to draw it that way because that turns out to be even more confusing  than drawing it this way.  People have a hard time seeing.  Okay, let's look.  The barium atoms are on the corners.  They're intersected by three planes.  Therefore they only count one-eighth.  Or if you imagine it's only the inner part on the corner, the outer parts are all gone.  That's one-eighth.  There's eight of them so there's one barium atom.  The titanium atoms completely inside and so there's one titanium per unit cell.  The six oxygen atoms are on the six faces.  They have one plane through them so they count half.  There's six of them.  Six times a half is three.  The charges also help us although the charges are not always listed with the unit cell.  Sometimes they aren't theirs.  But in this case they are.  It was listed plus two for barium.  Well that's an alkaline earth metal.  Plus four for titanium.  That's a common oxidation state for titanium.  And then three times two minus for oxygen.  This is six positive and six negative.  The salt's neutral just like sodium chloride is neutral.  Sodium plus chloride minus.  And so the formula is BATIO3.  And that's why it's called barium titanate.  It's purportedly being used as part of the new capacitor storage systems being investigated  for next generation vehicles.  So next generation vehicles they may have a big for electric vehicle.  They may have a big capacitor in the vehicle too in addition to the battery.  And when you really need to go the capacitor discharges and supplies you a lot of power  very quickly.  And then while you're coasting downhill the car is smart enough to charge the capacitor  back up like it does the battery.  Yeah.  What would happen on a test if you accidentally broke titanium, like titanium barium oxygen  3?  I'd give it to you because you aren't a chemist yet.  But the reason why it's called barium titanate and sodium chloride when you see the one  that has the IUM that's first.  IUM?  Yeah.  Sodium.  Barium.  Okay.  Otherwise it'd be called titanium bariate or something like that if it were backwards.  But for now we won't split hairs.  Okay.  If you get the right number of atoms we'll take it.  Okay.  All right.  Let's see.  Aha. A temperature sensitive, oops I meant compound.  I've got a temper, I'll fix that.  A temperature sensitive compound that is wet.  I can't heat it to dry it because if I heat it it decomposes.  It cooks.  Now I made this stuff in the lab and the last thing I want to do on the last step to dry  it out to weigh it is to cook it.  And so I want to get rid of the water but not by heating it up to 100 so that the water  vapor pressure is one atmosphere.  But I just want to heat it up to 40.  And if I know the enthalpy of vaporization of water then I should know if I have a pump  in a speedback what pressure I need to hold on the pump in order to be able to drive the  water off only at 40 Celsius.  I don't want the pressure to be higher than the vapor pressure of water at 40 Celsius.  If it's higher the water will go back onto the compound.  If my pressure is lower because I'm pumping fast enough then the water will just wander  off and I'll dry it out and I won't wreck the compound.  This is done all the time in the lab.  We need an equation then that relates delta H of vaporization to temperature and I see  ooh these are in Celsius.  Be careful.  While we have such an equation the Clausius-Clapeyron equation and it says if I know the vapor pressure  at one temperature then I can predict the vapor pressure at another temperature as long  as I know delta H but I know delta H and I know R should be fairly easy.  The only thing I have to be careful of is this 40 Celsius.  If I'm in a hurry I might put 1 over 100, 1 over 40 and I'll get into trouble right  away.  Let's insert all the numbers.  I'm calling conditions one.  Conditions one is water at 100 Celsius and one atmosphere pressure.  So I put P1, 1 atmosphere, P2 I want to figure out.  This is delta H in joules.  This is R in joules.  Formol goes away.  Calvin to the minus 1 that kills this.  Good.  The log of something is dimensionless.  I convert the 100 to 373.15 and I convert the 40 to 313.15 and then I solve all this  stuff and I get a number plus 2.5104 and then I take the exponential function of both sides  which just gets rid of the log.  I have one atmosphere divided by P2 is equal to the exponential function or e to the 2.5.  I punch e to the 2.5 on my calculator.  I get 12.31, therefore P2 is 1 over 12.31.  P2 is 0.0812 atmospheres or 61.7 Tor.  Oftentimes the meter will actually be listed in Tor just because people find it easier to  read 60 Tor than 0.08 something in atmosphere.  I know the vapor pressure of water is one atmosphere at its boiling point.  That I do know.  We can achieve this with any decent pump.  We had to make some assumptions that the material itself has very low vapor pressure  if the material has high vapor pressure will actually pump it off too and you have to be  careful sometimes depending what you've got.  Otherwise you end up pumping your product into the pump oil of the pump and then people  get very angry with you when you pump things into the pump oil because that wrecks the  pump oil for the next person.  That's one.  52.  A careless scientist has measured the vapor pressure of toluene.  That's the stuff in airplane glue that kids got into for a while.  None of them were chemists I assure you.  Chemists do not sniff anything ever.  I measured the vapor pressure of toluene in atmospheres here.  The boiling point of toluene is about 110.  To me this data looks okay.  And then after the measurement, now the goal of the project was to determine delta H of  vaporization for toluene.  Well I've got all this data.  This is much, much better than two points because if I can plot this data as a straight  line I can then do linear regression and I can get a great line through all of it.  And then I can get the slope of that line and that's minus delta H over R. So I can  get it.  Just have to do a little analysis.  Well here's what happened.  He plots log P versus one over T and comes to you and says help boss, help.  It's not straight.  What's going wrong?  He took the log okay I guess.  First of all what's wrong with this graph?  The axes are not labeled with the units.  Before you see a graph where the axes are not labeled, stand back.  Don't start looking at the graph.  Try to figure out what the units were.  He had things like 20 degrees and I notice he's got 05 and I notice that one over 20  is 0.05.  And so I figured this guy's adult.  What he's done is he's plotted the log of the pressure okay but he's plotted it versus  one over T in Celsius.  And that's why it's curved because it has to be one over T in Kelvin and he's careless  because he didn't put the units here which should be K to the minus one or in his case  degrees C to the minus one.  If you would have seen degrees C to the minus one you would have said hey that's wrong.  You never plot anything in chemistry like that.  We always use Kelvin and therefore if you go back and do it and so here's the conclusion.  The data's okay.  The graph doesn't have units.  We can see that the log of the pressure's okay because you can take the log of that and  the reference pressure is one atmosphere.  But it's in Celsius okay.  And what I'd like you to do is go back, convert it to Kelvin, plot it and see if it's straight.  And then here are the last important points for Tuesday.  First, same seating chart.  Second, we have to do some spot roll taking.  Therefore make sure you have your ID because somebody will come around and say you're in  G7 or you Joe Blow.  Third, practice.  And finally, don't count on looking things up in your notes.  Just slow algorithm.  And I hope you do well.
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